diff --git a/include/swift/AST/DiagnosticsSema.def b/include/swift/AST/DiagnosticsSema.def
index d0e7a3fa5105e..3716b949a6ff4 100644
--- a/include/swift/AST/DiagnosticsSema.def
+++ b/include/swift/AST/DiagnosticsSema.def
@@ -197,6 +197,9 @@ ERROR(cannot_match_expr_tuple_pattern_with_nontuple_value,none,
 ERROR(cannot_match_unresolved_expr_pattern_with_value,none,
       "pattern cannot match values of type %0",
       (Type))
+ERROR(cannot_match_value_with_pattern,none,
+      "pattern of type %1 cannot match %0",
+      (Type, Type))
 
 ERROR(cannot_reference_compare_types,none,
       "cannot check reference equality of functions; operands here have types "
diff --git a/include/swift/Sema/CompletionContextFinder.h b/include/swift/Sema/CompletionContextFinder.h
index 51dc3bfd515e2..dce6572908b7a 100644
--- a/include/swift/Sema/CompletionContextFinder.h
+++ b/include/swift/Sema/CompletionContextFinder.h
@@ -20,6 +20,10 @@
 
 namespace swift {
 
+namespace constraints {
+class SyntacticElementTarget;
+}
+
 class CompletionContextFinder : public ASTWalker {
   enum class ContextKind {
     FallbackExpression,
@@ -53,12 +57,9 @@ class CompletionContextFinder : public ASTWalker {
     return MacroWalking::Arguments;
   }
 
-  /// Finder for completion contexts within the provided initial expression.
-  CompletionContextFinder(ASTNode initialNode, DeclContext *DC)
-      : InitialExpr(initialNode.dyn_cast<Expr *>()), InitialDC(DC) {
-    assert(DC);
-    initialNode.walk(*this);
-  };
+  /// Finder for completion contexts within the provided SyntacticElementTarget.
+  CompletionContextFinder(constraints::SyntacticElementTarget target,
+                          DeclContext *DC);
 
   /// Finder for completion contexts within the outermost non-closure context of
   /// the code completion expression's direct context.
diff --git a/include/swift/Sema/ConstraintLocator.h b/include/swift/Sema/ConstraintLocator.h
index 71fd781385d97..981b70188ebfc 100644
--- a/include/swift/Sema/ConstraintLocator.h
+++ b/include/swift/Sema/ConstraintLocator.h
@@ -318,6 +318,9 @@ class ConstraintLocator : public llvm::FoldingSetNode {
   /// otherwise \c nullptr.
   NullablePtr<Pattern> getPatternMatch() const;
 
+  /// Whether the locator in question is for a pattern match.
+  bool isForPatternMatch() const;
+
   /// Returns true if \p locator is ending with either of the following
   ///  - Member
   ///  - Member -> KeyPathDynamicMember
diff --git a/include/swift/Sema/ConstraintLocatorPathElts.def b/include/swift/Sema/ConstraintLocatorPathElts.def
index 62649588386f0..c60640e114cd9 100644
--- a/include/swift/Sema/ConstraintLocatorPathElts.def
+++ b/include/swift/Sema/ConstraintLocatorPathElts.def
@@ -225,6 +225,10 @@ CUSTOM_LOCATOR_PATH_ELT(TernaryBranch)
 /// Performing a pattern patch.
 CUSTOM_LOCATOR_PATH_ELT(PatternMatch)
 
+/// The constraint that models the allowed implicit casts for
+/// an EnumElementPattern.
+SIMPLE_LOCATOR_PATH_ELT(EnumPatternImplicitCastMatch)
+
 /// Points to a particular attribute associated with one of
 /// the arguments e.g. `inout` or its type e.g. `@escaping`.
 ///
diff --git a/include/swift/Sema/ConstraintSystem.h b/include/swift/Sema/ConstraintSystem.h
index 1951e3ad1c05d..6d6bb23a2712c 100644
--- a/include/swift/Sema/ConstraintSystem.h
+++ b/include/swift/Sema/ConstraintSystem.h
@@ -1500,6 +1500,10 @@ class Solution {
   llvm::SmallMapVector<const CaseLabelItem *, CaseLabelItemInfo, 4>
       caseLabelItems;
 
+  /// A map of expressions to the ExprPatterns that they are being solved as
+  /// a part of.
+  llvm::SmallMapVector<Expr *, ExprPattern *, 2> exprPatterns;
+
   /// The set of parameters that have been inferred to be 'isolated'.
   llvm::SmallVector<ParamDecl *, 2> isolatedParams;
 
@@ -1685,6 +1689,16 @@ class Solution {
         : nullptr;
   }
 
+  /// Retrieve the solved ExprPattern that corresponds to provided
+  /// sub-expression.
+  NullablePtr<ExprPattern> getExprPatternFor(Expr *E) const {
+    auto result = exprPatterns.find(E);
+    if (result == exprPatterns.end())
+      return nullptr;
+
+    return result->second;
+  }
+
   /// This method implements functionality of `Expr::isTypeReference`
   /// with data provided by a given solution.
   bool isTypeReference(Expr *E) const;
@@ -2148,6 +2162,10 @@ class ConstraintSystem {
   llvm::SmallMapVector<const CaseLabelItem *, CaseLabelItemInfo, 4>
       caseLabelItems;
 
+  /// A map of expressions to the ExprPatterns that they are being solved as
+  /// a part of.
+  llvm::SmallMapVector<Expr *, ExprPattern *, 2> exprPatterns;
+
   /// The set of parameters that have been inferred to be 'isolated'.
   llvm::SmallSetVector<ParamDecl *, 2> isolatedParams;
 
@@ -2745,6 +2763,9 @@ class ConstraintSystem {
     /// The length of \c caseLabelItems.
     unsigned numCaseLabelItems;
 
+    /// The length of \c exprPatterns.
+    unsigned numExprPatterns;
+
     /// The length of \c isolatedParams.
     unsigned numIsolatedParams;
 
@@ -3166,6 +3187,15 @@ class ConstraintSystem {
     caseLabelItems[item] = info;
   }
 
+  /// Record a given ExprPattern as the parent of its sub-expression.
+  void setExprPatternFor(Expr *E, ExprPattern *EP) {
+    assert(E);
+    assert(EP);
+    auto inserted = exprPatterns.insert({E, EP}).second;
+    assert(inserted && "Mapping already defined?");
+    (void)inserted;
+  }
+
   Optional<CaseLabelItemInfo> getCaseLabelItemInfo(
       const CaseLabelItem *item) const {
     auto known = caseLabelItems.find(item);
@@ -4315,6 +4345,11 @@ class ConstraintSystem {
   /// \returns \c true if constraint generation failed, \c false otherwise
   bool generateConstraints(SingleValueStmtExpr *E);
 
+  /// Generate constraints for an array of ExprPatterns, forming a conjunction
+  /// that solves each expression in turn.
+  void generateConstraints(ArrayRef<ExprPattern *> exprPatterns,
+                           ConstraintLocatorBuilder locator);
+
   /// Generate constraints for the given (unchecked) expression.
   ///
   /// \returns a possibly-sanitized expression, or null if an error occurred.
diff --git a/lib/IDE/TypeCheckCompletionCallback.cpp b/lib/IDE/TypeCheckCompletionCallback.cpp
index d2f652bd84a68..9739a53fbd679 100644
--- a/lib/IDE/TypeCheckCompletionCallback.cpp
+++ b/lib/IDE/TypeCheckCompletionCallback.cpp
@@ -81,7 +81,13 @@ Type swift::ide::getTypeForCompletion(const constraints::Solution &S,
 /// \endcode
 /// If the code completion expression occurs in such an AST, return the
 /// declaration of the \c $match variable, otherwise return \c nullptr.
-static VarDecl *getMatchVarIfInPatternMatch(Expr *E, ConstraintSystem &CS) {
+static VarDecl *getMatchVarIfInPatternMatch(Expr *E, const Solution &S) {
+  if (auto EP = S.getExprPatternFor(E))
+    return EP.get()->getMatchVar();
+
+  // TODO: Once ExprPattern type-checking is fully moved into the solver,
+  // the below can be deleted.
+  auto &CS = S.getConstraintSystem();
   auto &Context = CS.getASTContext();
 
   auto *Binary = dyn_cast_or_null<BinaryExpr>(CS.getParentExpr(E));
@@ -109,20 +115,21 @@ static VarDecl *getMatchVarIfInPatternMatch(Expr *E, ConstraintSystem &CS) {
 }
 
 Type swift::ide::getPatternMatchType(const constraints::Solution &S, Expr *E) {
-  if (auto MatchVar = getMatchVarIfInPatternMatch(E, S.getConstraintSystem())) {
-    Type MatchVarType;
-    // If the MatchVar has an explicit type, it's not part of the solution. But
-    // we can look it up in the constraint system directly.
-    if (auto T = S.getConstraintSystem().getVarType(MatchVar)) {
-      MatchVarType = T;
-    } else {
-      MatchVarType = getTypeForCompletion(S, MatchVar);
-    }
-    if (MatchVarType) {
-      return MatchVarType;
-    }
-  }
-  return nullptr;
+  auto MatchVar = getMatchVarIfInPatternMatch(E, S);
+  if (!MatchVar)
+    return nullptr;
+
+  if (S.hasType(MatchVar))
+    return S.getResolvedType(MatchVar);
+
+  // If the ExprPattern wasn't solved as part of the constraint system, it's
+  // not part of the solution.
+  // TODO: This can be removed once ExprPattern type-checking is fully part
+  // of the constraint system.
+  if (auto T = S.getConstraintSystem().getVarType(MatchVar))
+    return T;
+
+  return getTypeForCompletion(S, MatchVar);
 }
 
 void swift::ide::getSolutionSpecificVarTypes(
diff --git a/lib/Sema/BuilderTransform.cpp b/lib/Sema/BuilderTransform.cpp
index 43fa783a0d786..b6ae98679227c 100644
--- a/lib/Sema/BuilderTransform.cpp
+++ b/lib/Sema/BuilderTransform.cpp
@@ -984,7 +984,8 @@ Optional<BraceStmt *> TypeChecker::applyResultBuilderBodyTransform(
     SmallVector<Solution, 4> solutions;
     cs.solveForCodeCompletion(solutions);
 
-    CompletionContextFinder analyzer(func, func->getDeclContext());
+    SyntacticElementTarget funcTarget(func);
+    CompletionContextFinder analyzer(funcTarget, func->getDeclContext());
     if (analyzer.hasCompletion()) {
       filterSolutionsForCodeCompletion(solutions, analyzer);
       for (const auto &solution : solutions) {
diff --git a/lib/Sema/CSApply.cpp b/lib/Sema/CSApply.cpp
index f6782775c5f23..f64ee2a0a82cb 100644
--- a/lib/Sema/CSApply.cpp
+++ b/lib/Sema/CSApply.cpp
@@ -8705,6 +8705,9 @@ namespace {
       return Action::SkipChildren();
     }
 
+    NullablePtr<Pattern>
+    rewritePattern(Pattern *pattern, DeclContext *DC);
+
     /// Rewrite the target, producing a new target.
     Optional<SyntacticElementTarget>
     rewriteTarget(SyntacticElementTarget target);
@@ -8951,12 +8954,68 @@ static Expr *wrapAsyncLetInitializer(
   return resultInit;
 }
 
+static Pattern *rewriteExprPattern(const SyntacticElementTarget &matchTarget,
+                                   Type patternTy,
+                                   RewriteTargetFn rewriteTarget) {
+  auto *EP = matchTarget.getExprPattern();
+
+  // See if we can simplify to another kind of pattern.
+  if (auto simplified = TypeChecker::trySimplifyExprPattern(EP, patternTy))
+    return simplified.get();
+
+  auto resultTarget = rewriteTarget(matchTarget);
+  if (!resultTarget)
+    return nullptr;
+
+  EP->setMatchExpr(resultTarget->getAsExpr());
+  EP->getMatchVar()->setInterfaceType(patternTy->mapTypeOutOfContext());
+  EP->setType(patternTy);
+  return EP;
+}
+
+/// Attempt to rewrite either an ExprPattern, or a pattern that was solved as
+/// an ExprPattern, e.g an EnumElementPattern that could not refer to an enum
+/// case.
+static Optional<Pattern *>
+tryRewriteExprPattern(Pattern *P, Solution &solution, Type patternTy,
+                      RewriteTargetFn rewriteTarget) {
+  // See if we have a match expression target.
+  auto matchTarget = solution.getTargetFor(P);
+  if (!matchTarget)
+    return None;
+
+  return rewriteExprPattern(*matchTarget, patternTy, rewriteTarget);
+}
+
+NullablePtr<Pattern> ExprWalker::rewritePattern(Pattern *pattern,
+                                                DeclContext *DC) {
+  auto &solution = Rewriter.solution;
+
+  // Figure out the pattern type.
+  auto patternTy = solution.getResolvedType(pattern);
+  patternTy = patternTy->reconstituteSugar(/*recursive=*/false);
+
+  // Coerce the pattern to its appropriate type.
+  TypeResolutionOptions patternOptions(TypeResolverContext::InExpression);
+  patternOptions |= TypeResolutionFlags::OverrideType;
+
+  auto tryRewritePattern = [&](Pattern *EP, Type ty) {
+    return ::tryRewriteExprPattern(
+        EP, solution, ty, [&](auto target) { return rewriteTarget(target); });
+  };
+
+  auto contextualPattern = ContextualPattern::forRawPattern(pattern, DC);
+  return TypeChecker::coercePatternToType(contextualPattern, patternTy,
+                                          patternOptions, tryRewritePattern);
+}
+
 /// Apply the given solution to the initialization target.
 ///
 /// \returns the resulting initialization expression.
 static Optional<SyntacticElementTarget>
 applySolutionToInitialization(Solution &solution, SyntacticElementTarget target,
-                              Expr *initializer) {
+                              Expr *initializer,
+                              RewriteTargetFn rewriteTarget) {
   auto wrappedVar = target.getInitializationWrappedVar();
   Type initType;
   if (wrappedVar) {
@@ -9021,10 +9080,14 @@ applySolutionToInitialization(Solution &solution, SyntacticElementTarget target,
 
   finalPatternType = finalPatternType->reconstituteSugar(/*recursive =*/false);
 
+  auto tryRewritePattern = [&](Pattern *EP, Type ty) {
+    return ::tryRewriteExprPattern(EP, solution, ty, rewriteTarget);
+  };
+
   // Apply the solution to the pattern as well.
   auto contextualPattern = target.getContextualPattern();
   if (auto coercedPattern = TypeChecker::coercePatternToType(
-          contextualPattern, finalPatternType, options)) {
+          contextualPattern, finalPatternType, options, tryRewritePattern)) {
     resultTarget.setPattern(coercedPattern);
   } else {
     return None;
@@ -9171,10 +9234,15 @@ static Optional<SyntacticElementTarget> applySolutionToForEachStmt(
     TypeResolutionOptions options(TypeResolverContext::ForEachStmt);
     options |= TypeResolutionFlags::OverrideType;
 
+    auto tryRewritePattern = [&](Pattern *EP, Type ty) {
+      return ::tryRewriteExprPattern(EP, solution, ty, rewriteTarget);
+    };
+
     // Apply the solution to the pattern as well.
     auto contextualPattern = target.getContextualPattern();
     auto coercedPattern = TypeChecker::coercePatternToType(
-        contextualPattern, forEachStmtInfo.initType, options);
+        contextualPattern, forEachStmtInfo.initType, options,
+        tryRewritePattern);
     if (!coercedPattern)
       return None;
 
@@ -9262,7 +9330,8 @@ ExprWalker::rewriteTarget(SyntacticElementTarget target) {
     switch (target.getExprContextualTypePurpose()) {
     case CTP_Initialization: {
       auto initResultTarget = applySolutionToInitialization(
-          solution, target, rewrittenExpr);
+          solution, target, rewrittenExpr,
+          [&](auto target) { return rewriteTarget(target); });
       if (!initResultTarget)
         return None;
 
@@ -9353,47 +9422,11 @@ ExprWalker::rewriteTarget(SyntacticElementTarget target) {
     ConstraintSystem &cs = solution.getConstraintSystem();
     auto info = *cs.getCaseLabelItemInfo(*caseLabelItem);
 
-    // Figure out the pattern type.
-    Type patternType = solution.simplifyType(solution.getType(info.pattern));
-    patternType = patternType->reconstituteSugar(/*recursive=*/false);
-
-    // Check whether this enum element is resolved via ~= application.
-    if (auto *enumElement = dyn_cast<EnumElementPattern>(info.pattern)) {
-      if (auto target = cs.getTargetFor(enumElement)) {
-        auto *EP = target->getExprPattern();
-        auto enumType = solution.getResolvedType(EP);
-
-        auto *matchCall = target->getAsExpr();
-
-        auto *result = matchCall->walk(*this);
-        if (!result)
-          return None;
-
-        {
-          auto *matchVar = EP->getMatchVar();
-          matchVar->setInterfaceType(enumType->mapTypeOutOfContext());
-        }
-
-        EP->setMatchExpr(result);
-        EP->setType(enumType);
-
-        (*caseLabelItem)->setPattern(EP, /*resolved=*/true);
-        return target;
-      }
-    }
-
-    // Coerce the pattern to its appropriate type.
-    TypeResolutionOptions patternOptions(TypeResolverContext::InExpression);
-    patternOptions |= TypeResolutionFlags::OverrideType;
-    auto contextualPattern =
-        ContextualPattern::forRawPattern(info.pattern,
-                                         target.getDeclContext());
-    if (auto coercedPattern = TypeChecker::coercePatternToType(
-            contextualPattern, patternType, patternOptions)) {
-      (*caseLabelItem)->setPattern(coercedPattern, /*resolved=*/true);
-    } else {
+    auto pattern = rewritePattern(info.pattern, target.getDeclContext());
+    if (!pattern)
       return None;
-    }
+
+    (*caseLabelItem)->setPattern(pattern.get(), /*resolved=*/true);
 
     // If there is a guard expression, coerce that.
     if (auto *guardExpr = info.guardExpr) {
@@ -9461,8 +9494,13 @@ ExprWalker::rewriteTarget(SyntacticElementTarget target) {
       options |= TypeResolutionFlags::OverrideType;
     }
 
+    auto tryRewritePattern = [&](Pattern *EP, Type ty) {
+      return ::tryRewriteExprPattern(
+          EP, solution, ty, [&](auto target) { return rewriteTarget(target); });
+    };
+
     if (auto coercedPattern = TypeChecker::coercePatternToType(
-            contextualPattern, patternType, options)) {
+            contextualPattern, patternType, options, tryRewritePattern)) {
       auto resultTarget = target;
       resultTarget.setPattern(coercedPattern);
       return resultTarget;
diff --git a/lib/Sema/CSDiagnostics.cpp b/lib/Sema/CSDiagnostics.cpp
index fc9b3cc28d9e3..241c849d5a80a 100644
--- a/lib/Sema/CSDiagnostics.cpp
+++ b/lib/Sema/CSDiagnostics.cpp
@@ -2715,6 +2715,19 @@ bool ContextualFailure::diagnoseAsError() {
     return false;
   }
 
+  case ConstraintLocator::EnumPatternImplicitCastMatch: {
+    // In this case, the types are reversed, as we are checking whether we
+    // can convert the pattern type to the context type.
+    std::swap(fromType, toType);
+    diagnostic = diag::cannot_match_value_with_pattern;
+    break;
+  }
+
+  case ConstraintLocator::PatternMatch: {
+    diagnostic = diag::cannot_match_value_with_pattern;
+    break;
+  }
+
   default:
     return false;
   }
@@ -2927,9 +2940,11 @@ bool ContextualFailure::diagnoseConversionToNil() const {
 void ContextualFailure::tryFixIts(InFlightDiagnostic &diagnostic) const {
   auto *locator = getLocator();
   // Can't apply any of the fix-its below if this failure
-  // is related to `inout` argument.
-  if (locator->isLastElement<LocatorPathElt::LValueConversion>())
+  // is related to `inout` argument, or a pattern mismatch.
+  if (locator->isLastElement<LocatorPathElt::LValueConversion>() ||
+      locator->isForPatternMatch()) {
     return;
+  }
 
   if (trySequenceSubsequenceFixIts(diagnostic))
     return;
@@ -3549,6 +3564,8 @@ ContextualFailure::getDiagnosticFor(ContextualTypePurpose context,
     return diag::cannot_convert_discard_value;
 
   case CTP_CaseStmt:
+    return diag::cannot_match_value_with_pattern;
+
   case CTP_ThrowStmt:
   case CTP_ForEachStmt:
   case CTP_ForEachSequence:
@@ -8756,7 +8773,7 @@ bool InvalidWeakAttributeUse::diagnoseAsError() {
     return false;
 
   auto *var = pattern->getDecl();
-  auto varType = OptionalType::get(getType(var));
+  auto varType = getType(var);
 
   auto diagnostic =
       emitDiagnosticAt(var, diag::invalid_ownership_not_optional,
diff --git a/lib/Sema/CSGen.cpp b/lib/Sema/CSGen.cpp
index efcfbc8123cd8..c30c94dbc2792 100644
--- a/lib/Sema/CSGen.cpp
+++ b/lib/Sema/CSGen.cpp
@@ -2438,37 +2438,21 @@ namespace {
     /// \param locator The locator to use for generated constraints and
     /// type variables.
     ///
-    /// \param externalPatternType The type imposed by the enclosing pattern,
-    /// if any. This will be non-null in cases where there is, e.g., a
-    /// pattern such as "is SubClass".
-    ///
     /// \param bindPatternVarsOneWay When true, generate fresh type variables
     /// for the types of each variable declared within the pattern, along
     /// with a one-way constraint binding that to the type to which the
     /// variable will be ascribed or inferred.
     Type getTypeForPattern(
        Pattern *pattern, ConstraintLocatorBuilder locator,
-       Type externalPatternType,
        bool bindPatternVarsOneWay,
        PatternBindingDecl *patternBinding = nullptr,
        unsigned patternBindingIndex = 0) {
-      // If there's no pattern, then we have an unknown subpattern. Create a
-      // type variable.
-      if (!pattern) {
-        return CS.createTypeVariable(CS.getConstraintLocator(locator),
-                                     TVO_CanBindToNoEscape);
-      }
+      assert(pattern);
 
       // Local function that must be called for each "return" throughout this
       // function, to set the type of the pattern.
       auto setType = [&](Type type) {
         CS.setType(pattern, type);
-        if (auto PE = dyn_cast<ExprPattern>(pattern)) {
-          // Set the type of the pattern's sub-expression as well, so code
-          // completion can retrieve the expression's type in case it is a code
-          // completion token.
-          CS.setType(PE->getSubExpr(), type);
-        }
         return type;
       };
 
@@ -2476,33 +2460,18 @@ namespace {
       case PatternKind::Paren: {
         auto *paren = cast<ParenPattern>(pattern);
 
-        // Parentheses don't affect the canonical type, but record them as
-        // type sugar.
-        if (externalPatternType &&
-            isa<ParenType>(externalPatternType.getPointer())) {
-          externalPatternType = cast<ParenType>(externalPatternType.getPointer())
-              ->getUnderlyingType();
-        }
-
         auto *subPattern = paren->getSubPattern();
         auto underlyingType = getTypeForPattern(
             subPattern,
             locator.withPathElement(LocatorPathElt::PatternMatch(subPattern)),
-            externalPatternType, bindPatternVarsOneWay);
-
-        if (!underlyingType)
-          return Type();
+            bindPatternVarsOneWay);
 
         return setType(ParenType::get(CS.getASTContext(), underlyingType));
       }
       case PatternKind::Binding: {
         auto *subPattern = cast<BindingPattern>(pattern)->getSubPattern();
-        auto type = getTypeForPattern(subPattern, locator, externalPatternType,
+        auto type = getTypeForPattern(subPattern, locator,
                                       bindPatternVarsOneWay);
-
-        if (!type)
-          return Type();
-
         // Var doesn't affect the type.
         return setType(type);
       }
@@ -2526,9 +2495,7 @@ namespace {
             locator.withPathElement(LocatorPathElt::PatternMatch(pattern));
 
         // Always prefer a contextual type when it's available.
-        if (externalPatternType) {
-          type = externalPatternType;
-        } else if (auto *initializer = getInitializerExpr()) {
+        if (auto *initializer = getInitializerExpr()) {
           // For initialization always assume a type of initializer.
           type = CS.getType(initializer)->getRValueType();
         } else {
@@ -2608,18 +2575,13 @@ namespace {
           // diagnostic in the middle of the solver path.
 
           CS.addConstraint(ConstraintKind::OneWayEqual, oneWayVarType,
-                           externalPatternType ? externalPatternType : varType,
-                           locator);
+                           varType, locator);
         }
 
         // Ascribe a type to the declaration so it's always available to
         // constraint system.
         if (oneWayVarType) {
           CS.setType(var, oneWayVarType);
-        } else if (externalPatternType) {
-          // If there is an externally imposed type, that's what the
-          // declaration is going to be bound to.
-          CS.setType(var, externalPatternType);
         } else {
           // Otherwise, let's use the type of the pattern. The type
           // of the declaration has to be r-value, so let's add an
@@ -2691,9 +2653,6 @@ namespace {
 
         Type type = TypeChecker::typeCheckPattern(contextualPattern);
 
-        if (!type)
-          return Type();
-
         // Look through reference storage types.
         type = type->getReferenceStorageReferent();
 
@@ -2708,13 +2667,13 @@ namespace {
         Type subPatternType = getTypeForPattern(
             subPattern,
             locator.withPathElement(LocatorPathElt::PatternMatch(subPattern)),
-            openedType, bindPatternVarsOneWay);
-
-        if (!subPatternType)
-          return Type();
+            bindPatternVarsOneWay);
 
+        // NOTE: The order here is important! Pattern matching equality is
+        // not symmetric (we need to fix that either by using a different
+        // constraint, or actually making it symmetric).
         CS.addConstraint(
-            ConstraintKind::Conversion, subPatternType, openedType,
+            ConstraintKind::Equal, openedType, subPatternType,
             locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
 
         // FIXME [OPAQUE SUPPORT]: the distinction between where we want opaque
@@ -2728,41 +2687,16 @@ namespace {
       case PatternKind::Tuple: {
         auto tuplePat = cast<TuplePattern>(pattern);
 
-        // If there's an externally-imposed type, decompose it into element
-        // types so long as we have the right number of such types.
-        SmallVector<AnyFunctionType::Param, 4> externalEltTypes;
-        if (externalPatternType) {
-          decomposeTuple(externalPatternType, externalEltTypes);
-
-          // If we have the wrong number of elements, we may not be able to
-          // provide more specific types.
-          if (tuplePat->getNumElements() != externalEltTypes.size()) {
-            externalEltTypes.clear();
-
-            // Implicit tupling.
-            if (tuplePat->getNumElements() == 1) {
-              externalEltTypes.push_back(
-                  AnyFunctionType::Param(externalPatternType));
-            }
-          }
-        }
-
         SmallVector<TupleTypeElt, 4> tupleTypeElts;
         tupleTypeElts.reserve(tuplePat->getNumElements());
         for (unsigned i = 0, e = tuplePat->getNumElements(); i != e; ++i) {
           auto &tupleElt = tuplePat->getElement(i);
-          Type externalEltType;
-          if (!externalEltTypes.empty())
-            externalEltType = externalEltTypes[i].getPlainType();
 
           auto *eltPattern = tupleElt.getPattern();
           Type eltTy = getTypeForPattern(
               eltPattern,
               locator.withPathElement(LocatorPathElt::PatternMatch(eltPattern)),
-              externalEltType, bindPatternVarsOneWay);
-
-          if (!eltTy)
-            return Type();
+              bindPatternVarsOneWay);
 
           tupleTypeElts.push_back(TupleTypeElt(eltTy, tupleElt.getLabel()));
         }
@@ -2771,28 +2705,12 @@ namespace {
       }
 
       case PatternKind::OptionalSome: {
-        // Remove an optional from the object type.
-        if (externalPatternType) {
-          Type objVar = CS.createTypeVariable(
-              CS.getConstraintLocator(
-                  locator.withPathElement(ConstraintLocator::OptionalPayload)),
-              TVO_CanBindToNoEscape);
-          CS.addConstraint(
-              ConstraintKind::OptionalObject, externalPatternType, objVar,
-              locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
-
-          externalPatternType = objVar;
-        }
-
         auto *subPattern = cast<OptionalSomePattern>(pattern)->getSubPattern();
         // The subpattern must have optional type.
         Type subPatternType = getTypeForPattern(
             subPattern,
             locator.withPathElement(LocatorPathElt::PatternMatch(subPattern)),
-            externalPatternType, bindPatternVarsOneWay);
-
-        if (!subPatternType)
-          return Type();
+            bindPatternVarsOneWay);
 
         return setType(OptionalType::get(subPatternType));
       }
@@ -2803,22 +2721,6 @@ namespace {
         const Type castType = resolveTypeReferenceInExpression(
             isPattern->getCastTypeRepr(), TypeResolverContext::InExpression,
             locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
-        if (!castType) return Type();
-
-        auto *subPattern = isPattern->getSubPattern();
-        Type subPatternType = getTypeForPattern(
-            subPattern,
-            locator.withPathElement(LocatorPathElt::PatternMatch(subPattern)),
-            castType, bindPatternVarsOneWay);
-
-        if (!subPatternType)
-          return Type();
-
-        // Make sure we can cast from the subpattern type to the type we're
-        // checking; if it's impossible, fail.
-        CS.addConstraint(
-            ConstraintKind::CheckedCast, subPatternType, castType,
-            locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
 
         // Allow `is` pattern to infer type from context which is then going
         // to be propaged down to its sub-pattern via conversion. This enables
@@ -2828,9 +2730,26 @@ namespace {
         auto isType =
             CS.createTypeVariable(CS.getConstraintLocator(pattern),
                                   TVO_CanBindToNoEscape | TVO_CanBindToHole);
+
+        // Make sure we can cast from the subpattern type to the type we're
+        // checking; if it's impossible, fail.
         CS.addConstraint(
-            ConstraintKind::Conversion, subPatternType, isType,
+            ConstraintKind::CheckedCast, isType, castType,
             locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
+
+        if (auto *subPattern = isPattern->getSubPattern()) {
+          auto subPatternType = getTypeForPattern(
+              subPattern,
+              locator.withPathElement(LocatorPathElt::PatternMatch(subPattern)),
+              bindPatternVarsOneWay);
+
+          // NOTE: The order here is important! Pattern matching equality is
+          // not symmetric (we need to fix that either by using a different
+          // constraint, or actually making it symmetric).
+          CS.addConstraint(
+              ConstraintKind::Equal, castType, subPatternType,
+              locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
+        }
         return setType(isType);
       }
 
@@ -2864,6 +2783,9 @@ namespace {
         if (dyn_cast_or_null<TuplePattern>(enumPattern->getSubPattern()))
           functionRefKind = FunctionRefKind::Compound;
 
+        auto patternLocator =
+            locator.withPathElement(LocatorPathElt::PatternMatch(pattern));
+
         if (enumPattern->getParentType() || enumPattern->getParentTypeRepr()) {
           // Resolve the parent type.
           const auto parentType = [&] {
@@ -2889,42 +2811,25 @@ namespace {
                 TypeResolverContext::InExpression, patternMatchLoc);
           }();
 
-          if (!parentType)
-            return Type();
-
           // Perform member lookup into the parent's metatype.
           Type parentMetaType = MetatypeType::get(parentType);
-          CS.addValueMemberConstraint(
-              parentMetaType, enumPattern->getName(), memberType, CurDC,
-              functionRefKind, {},
-              CS.getConstraintLocator(locator,
-                                      LocatorPathElt::PatternMatch(pattern)));
+          CS.addValueMemberConstraint(parentMetaType, enumPattern->getName(),
+                                      memberType, CurDC, functionRefKind, {},
+                                      patternLocator);
 
           // Parent type needs to be convertible to the pattern type; this
           // accounts for cases where the pattern type is existential.
           CS.addConstraint(
               ConstraintKind::Conversion, parentType, patternType,
-              locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
+              patternLocator.withPathElement(
+                  ConstraintLocator::EnumPatternImplicitCastMatch));
 
           baseType = parentType;
-          // Perform member lookup into the external pattern metatype. e.g.
-          // `case let .test(tuple) as Test`.
-        } else if (externalPatternType) {
-          Type externalMetaType = MetatypeType::get(externalPatternType);
-
-          CS.addValueMemberConstraint(
-              externalMetaType, enumPattern->getName(), memberType, CurDC,
-              functionRefKind, {},
-              CS.getConstraintLocator(locator,
-                                      LocatorPathElt::PatternMatch(pattern)));
-
-          baseType = externalPatternType;
         } else {
           // Use the pattern type for member lookup.
           CS.addUnresolvedValueMemberConstraint(
               MetatypeType::get(patternType), enumPattern->getName(),
-              memberType, CurDC, functionRefKind,
-              locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
+              memberType, CurDC, functionRefKind, patternLocator);
 
           baseType = patternType;
         }
@@ -2936,10 +2841,7 @@ namespace {
           Type subPatternType = getTypeForPattern(
               subPattern,
               locator.withPathElement(LocatorPathElt::PatternMatch(subPattern)),
-              Type(), bindPatternVarsOneWay);
-
-          if (!subPatternType)
-            return Type();
+              bindPatternVarsOneWay);
 
           SmallVector<AnyFunctionType::Param, 4> params;
           decomposeTuple(subPatternType, params);
@@ -2957,28 +2859,29 @@ namespace {
           // FIXME: Verify ExtInfo state is correct, not working by accident.
           FunctionType::ExtInfo info;
           Type functionType = FunctionType::get(params, outputType, info);
-          // TODO: Convert to FunctionInput/FunctionResult constraints.
-          CS.addConstraint(
-              ConstraintKind::Equal, functionType, memberType,
-              locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
 
-          CS.addConstraint(
-              ConstraintKind::Conversion, outputType, baseType,
-              locator.withPathElement(LocatorPathElt::PatternMatch(pattern)));
+          // TODO: Convert to own constraint? Note that ApplicableFn isn't quite
+          // right, as pattern matching has data flowing *into* the apply result
+          // and call arguments, not the other way around.
+          // NOTE: The order here is important! Pattern matching equality is
+          // not symmetric (we need to fix that either by using a different
+          // constraint, or actually making it symmetric).
+          CS.addConstraint(ConstraintKind::Equal, functionType, memberType,
+                           patternLocator);
+
+          CS.addConstraint(ConstraintKind::Conversion, outputType, baseType,
+                           patternLocator);
         }
 
         return setType(patternType);
       }
 
-      // Refutable patterns occur when checking the PatternBindingDecls in an
-      // if/let or while/let condition.  They always require an initial value,
-      // so they always allow unspecified types.
-      case PatternKind::Expr:
-        // TODO: we could try harder here, e.g. for enum elements to provide the
-        // enum type.
-        return setType(
-            CS.createTypeVariable(CS.getConstraintLocator(locator),
-                                  TVO_CanBindToNoEscape | TVO_CanBindToHole));
+      case PatternKind::Expr: {
+        // We generate constraints for ExprPatterns in a separate pass. For
+        // now, just create a type variable.
+        return setType(CS.createTypeVariable(CS.getConstraintLocator(locator),
+                                             TVO_CanBindToNoEscape));
+      }
       }
 
       llvm_unreachable("Unhandled pattern kind");
@@ -4421,16 +4324,18 @@ bool ConstraintSystem::generateWrappedPropertyTypeConstraints(
 static bool generateInitPatternConstraints(ConstraintSystem &cs,
                                            SyntacticElementTarget target,
                                            Expr *initializer) {
-  auto pattern = target.getInitializationPattern();
   auto locator = cs.getConstraintLocator(
       initializer, LocatorPathElt::ContextualType(CTP_Initialization));
-  Type patternType = cs.generateConstraints(
-      pattern, locator, target.shouldBindPatternVarsOneWay(),
-      target.getInitializationPatternBindingDecl(),
-      target.getInitializationPatternBindingIndex());
 
-  if (!patternType)
-    return true;
+  Type patternType;
+  if (auto pattern = target.getInitializationPattern()) {
+    patternType = cs.generateConstraints(
+        pattern, locator, target.shouldBindPatternVarsOneWay(),
+        target.getInitializationPatternBindingDecl(),
+        target.getInitializationPatternBindingIndex());
+  } else {
+    patternType = cs.createTypeVariable(locator, TVO_CanBindToNoEscape);
+  }
 
   if (auto wrappedVar = target.getInitializationWrappedVar())
     return cs.generateWrappedPropertyTypeConstraints(
@@ -4845,8 +4750,20 @@ Type ConstraintSystem::generateConstraints(
     bool bindPatternVarsOneWay, PatternBindingDecl *patternBinding,
     unsigned patternIndex) {
   ConstraintGenerator cg(*this, nullptr);
-  return cg.getTypeForPattern(pattern, locator, Type(), bindPatternVarsOneWay,
-                              patternBinding, patternIndex);
+  auto ty = cg.getTypeForPattern(pattern, locator, bindPatternVarsOneWay,
+                                 patternBinding, patternIndex);
+  assert(ty);
+
+  // Gather the ExprPatterns, and form a conjunction for their expressions.
+  SmallVector<ExprPattern *, 4> exprPatterns;
+  pattern->forEachNode([&](Pattern *P) {
+    if (auto *EP = dyn_cast<ExprPattern>(P))
+      exprPatterns.push_back(EP);
+  });
+  if (!exprPatterns.empty())
+    generateConstraints(exprPatterns, getConstraintLocator(pattern));
+
+  return ty;
 }
 
 bool ConstraintSystem::generateConstraints(StmtCondition condition,
diff --git a/lib/Sema/CSSimplify.cpp b/lib/Sema/CSSimplify.cpp
index 2a638c3a8c06f..b2a7e3b74ec95 100644
--- a/lib/Sema/CSSimplify.cpp
+++ b/lib/Sema/CSSimplify.cpp
@@ -2165,7 +2165,9 @@ class TupleMatcher {
       const auto &elt2 = tuple2->getElement(i);
 
       if (inPatternMatchingContext) {
-        if (elt1.hasName() && elt1.getName() != elt2.getName())
+        // FIXME: The fact that this isn't symmetric is wrong since this logic
+        // is called for bind and equal constraints...
+        if (elt2.hasName() && elt1.getName() != elt2.getName())
           return true;
       } else {
         // If the names don't match, we have a conflict.
@@ -3523,21 +3525,12 @@ ConstraintSystem::matchFunctionTypes(FunctionType *func1, FunctionType *func2,
       // FIXME: We should check value ownership too, but it's not completely
       // trivial because of inout-to-pointer conversions.
 
-      // For equality contravariance doesn't matter, but let's make sure
-      // that types are matched in original order because that is important
-      // when function types are equated as part of pattern matching.
-      auto paramType1 = kind == ConstraintKind::Equal ? func1Param.getOldType()
-                                                      : func2Param.getOldType();
-
-      auto paramType2 = kind == ConstraintKind::Equal ? func2Param.getOldType()
-                                                      : func1Param.getOldType();
-
-      // Compare the parameter types.
-      auto result = matchTypes(paramType1, paramType2, subKind, subflags,
-                               (func1Params.size() == 1
-                                ? argumentLocator
-                                : argumentLocator.withPathElement(
-                                      LocatorPathElt::TupleElement(i))));
+      // Compare the parameter types, taking contravariance into account.
+      auto result = matchTypes(
+          func2Param.getOldType(), func1Param.getOldType(), subKind, subflags,
+          (func1Params.size() == 1 ? argumentLocator
+                                   : argumentLocator.withPathElement(
+                                         LocatorPathElt::TupleElement(i))));
       if (result.isFailure())
         return result;
     }
@@ -6367,8 +6360,20 @@ bool ConstraintSystem::repairFailures(
     break;
   }
 
+  case ConstraintLocator::EnumPatternImplicitCastMatch: {
+    // If either type is a placeholder, consider this fixed.
+    if (lhs->isPlaceholder() || rhs->isPlaceholder())
+      return true;
+
+    conversionsOrFixes.push_back(ContextualMismatch::create(
+        *this, lhs, rhs, getConstraintLocator(locator)));
+    break;
+  }
+
   case ConstraintLocator::PatternMatch: {
     auto *pattern = elt.castTo<LocatorPathElt::PatternMatch>().getPattern();
+
+    // TODO: We ought to introduce a new locator element for this.
     bool isMemberMatch =
         lhs->is<FunctionType>() && isa<EnumElementPattern>(pattern);
 
@@ -6383,13 +6388,12 @@ bool ConstraintSystem::repairFailures(
     if (lhs->isPlaceholder() || rhs->isPlaceholder())
       return true;
 
-    // If member reference didn't match expected pattern,
-    // let's consider that a contextual mismatch.
     if (isMemberMatch) {
       recordAnyTypeVarAsPotentialHole(lhs);
       recordAnyTypeVarAsPotentialHole(rhs);
       conversionsOrFixes.push_back(AllowAssociatedValueMismatch::create(
           *this, lhs, rhs, getConstraintLocator(locator)));
+      break;
     }
 
     // `weak` declaration with an explicit non-optional type e.g.
@@ -6402,7 +6406,7 @@ bool ConstraintSystem::repairFailures(
         if (auto *OA = var->getAttrs().getAttribute<ReferenceOwnershipAttr>())
           ROK = OA->get();
 
-        if (!rhs->getOptionalObjectType() &&
+        if (!lhs->getOptionalObjectType() &&
             optionalityOf(ROK) == ReferenceOwnershipOptionality::Required) {
           conversionsOrFixes.push_back(
               AllowNonOptionalWeak::create(*this, getConstraintLocator(NP)));
@@ -6411,6 +6415,9 @@ bool ConstraintSystem::repairFailures(
       }
     }
 
+    conversionsOrFixes.push_back(ContextualMismatch::create(
+        *this, lhs, rhs, getConstraintLocator(locator)));
+
     break;
   }
 
@@ -14833,8 +14840,10 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyFixConstraint(
     if (recordFix(fix))
       return SolutionKind::Error;
 
-    (void)matchTypes(type1, OptionalType::get(type2),
-                     ConstraintKind::Conversion,
+    // NOTE: The order here is important! Pattern matching equality is
+    // not symmetric (we need to fix that either by using a different
+    // constraint, or actually making it symmetric).
+    (void)matchTypes(OptionalType::get(type1), type2, ConstraintKind::Equal,
                      TypeMatchFlags::TMF_ApplyingFix, locator);
 
     return SolutionKind::Solved;
diff --git a/lib/Sema/CSSolver.cpp b/lib/Sema/CSSolver.cpp
index e80def2f385f1..97dcdef70744b 100644
--- a/lib/Sema/CSSolver.cpp
+++ b/lib/Sema/CSSolver.cpp
@@ -195,6 +195,7 @@ Solution ConstraintSystem::finalize() {
 
   solution.targets = targets;
   solution.caseLabelItems = caseLabelItems;
+  solution.exprPatterns = exprPatterns;
   solution.isolatedParams.append(isolatedParams.begin(), isolatedParams.end());
   solution.preconcurrencyClosures.append(preconcurrencyClosures.begin(),
                                          preconcurrencyClosures.end());
@@ -327,6 +328,9 @@ void ConstraintSystem::applySolution(const Solution &solution) {
     isolatedParams.insert(param);
   }
 
+  for (auto &pair : solution.exprPatterns)
+    exprPatterns.insert(pair);
+
   for (auto closure : solution.preconcurrencyClosures) {
     preconcurrencyClosures.insert(closure);
   }
@@ -621,6 +625,7 @@ ConstraintSystem::SolverScope::SolverScope(ConstraintSystem &cs)
   numContextualTypes = cs.contextualTypes.size();
   numTargets = cs.targets.size();
   numCaseLabelItems = cs.caseLabelItems.size();
+  numExprPatterns = cs.exprPatterns.size();
   numIsolatedParams = cs.isolatedParams.size();
   numPreconcurrencyClosures = cs.preconcurrencyClosures.size();
   numImplicitValueConversions = cs.ImplicitValueConversions.size();
@@ -737,6 +742,9 @@ ConstraintSystem::SolverScope::~SolverScope() {
   // Remove any case label item infos.
   truncate(cs.caseLabelItems, numCaseLabelItems);
 
+  // Remove any ExprPattern mappings.
+  truncate(cs.exprPatterns, numExprPatterns);
+
   // Remove any isolated parameters.
   truncate(cs.isolatedParams, numIsolatedParams);
 
diff --git a/lib/Sema/CSSyntacticElement.cpp b/lib/Sema/CSSyntacticElement.cpp
index 43e0ac33a50c9..8fdec6b319a5d 100644
--- a/lib/Sema/CSSyntacticElement.cpp
+++ b/lib/Sema/CSSyntacticElement.cpp
@@ -410,7 +410,7 @@ ElementInfo makeJoinElement(ConstraintSystem &cs, TypeJoinExpr *join,
 
 struct SyntacticElementContext
     : public llvm::PointerUnion<AbstractFunctionDecl *, AbstractClosureExpr *,
-                                SingleValueStmtExpr *> {
+                                SingleValueStmtExpr *, ExprPattern *> {
   // Inherit the constructors from PointerUnion.
   using PointerUnion::PointerUnion;
 
@@ -441,6 +441,10 @@ struct SyntacticElementContext
     return context;
   }
 
+  static SyntacticElementContext forExprPattern(ExprPattern *EP) {
+    return SyntacticElementContext{EP};
+  }
+
   DeclContext *getAsDeclContext() const {
     if (auto *fn = this->dyn_cast<AbstractFunctionDecl *>()) {
       return fn;
@@ -448,6 +452,8 @@ struct SyntacticElementContext
       return closure;
     } else if (auto *SVE = dyn_cast<SingleValueStmtExpr *>()) {
       return SVE->getDeclContext();
+    } else if (auto *EP = dyn_cast<ExprPattern *>()) {
+      return EP->getDeclContext();
     } else {
       llvm_unreachable("unsupported kind");
     }
@@ -519,7 +525,32 @@ class SyntacticElementConstraintGenerator
                                       ConstraintLocator *locator)
       : cs(cs), context(context), locator(locator) {}
 
-  void visitPattern(Pattern *pattern, ContextualTypeInfo context) {
+  void visitExprPattern(ExprPattern *EP) {
+    auto target = SyntacticElementTarget::forExprPattern(EP);
+
+    if (cs.preCheckTarget(target, /*replaceInvalidRefWithErrors=*/true,
+                          /*leaveClosureBodyUnchecked=*/false)) {
+      hadError = true;
+      return;
+    }
+    cs.setType(EP->getMatchVar(), cs.getType(EP));
+
+    if (cs.generateConstraints(target)) {
+      hadError = true;
+      return;
+    }
+    cs.setTargetFor(EP, target);
+    cs.setExprPatternFor(EP->getSubExpr(), EP);
+  }
+
+  void visitPattern(Pattern *pattern, ContextualTypeInfo contextInfo) {
+    if (context.is<ExprPattern *>()) {
+      // This is for an ExprPattern conjunction, go ahead and generate
+      // constraints for the match expression.
+      visitExprPattern(cast<ExprPattern>(pattern));
+      return;
+    }
+
     auto parentElement =
         locator->getLastElementAs<LocatorPathElt::SyntacticElement>();
 
@@ -535,7 +566,7 @@ class SyntacticElementConstraintGenerator
       }
 
       if (isa<CaseStmt>(stmt)) {
-        visitCaseItemPattern(pattern, context);
+        visitCaseItemPattern(pattern, contextInfo);
         return;
       }
     }
@@ -626,8 +657,11 @@ class SyntacticElementConstraintGenerator
 
     // Convert the contextual type to the pattern, which establishes the
     // bindings.
-    cs.addConstraint(ConstraintKind::Conversion, context.getType(), patternType,
-                     locator);
+    auto *loc = cs.getConstraintLocator(
+        locator, {LocatorPathElt::PatternMatch(pattern),
+                  LocatorPathElt::ContextualType(context.purpose)});
+    cs.addConstraint(ConstraintKind::Equal, context.getType(), patternType,
+                     loc);
 
     // For any pattern variable that has a parent variable (i.e., another
     // pattern variable with the same name in the same case), require that
@@ -1438,6 +1472,24 @@ bool ConstraintSystem::generateConstraints(SingleValueStmtExpr *E) {
   return generator.hadError;
 }
 
+void ConstraintSystem::generateConstraints(ArrayRef<ExprPattern *> exprPatterns,
+                                           ConstraintLocatorBuilder locator) {
+  // Form a conjunction of ExprPattern elements, isolated from the rest of the
+  // pattern.
+  SmallVector<ElementInfo> elements;
+  SmallVector<TypeVariableType *, 2> referencedTypeVars;
+  for (auto *EP : exprPatterns) {
+    auto ty = getType(EP)->castTo<TypeVariableType>();
+    referencedTypeVars.push_back(ty);
+
+    ContextualTypeInfo context(ty, CTP_ExprPattern);
+    elements.push_back(makeElement(EP, getConstraintLocator(EP), context));
+  }
+  auto *loc = getConstraintLocator(locator);
+  createConjunction(*this, elements, loc, /*isIsolated*/ true,
+                    referencedTypeVars);
+}
+
 bool ConstraintSystem::isInResultBuilderContext(ClosureExpr *closure) const {
   if (!closure->hasSingleExpressionBody()) {
     auto *DC = closure->getParent();
@@ -1488,6 +1540,8 @@ ConstraintSystem::simplifySyntacticElementConstraint(
     context = SyntacticElementContext::forFunction(fn);
   } else if (auto *SVE = getAsExpr<SingleValueStmtExpr>(anchor)) {
     context = SyntacticElementContext::forSingleValueStmtExpr(SVE);
+  } else if (auto *EP = getAsPattern<ExprPattern>(anchor)) {
+    context = SyntacticElementContext::forExprPattern(EP);
   } else {
     return SolutionKind::Error;
   }
diff --git a/lib/Sema/CompletionContextFinder.cpp b/lib/Sema/CompletionContextFinder.cpp
index f4ef0f7a9336f..9279a038d160a 100644
--- a/lib/Sema/CompletionContextFinder.cpp
+++ b/lib/Sema/CompletionContextFinder.cpp
@@ -12,10 +12,19 @@
 
 #include "swift/Sema/CompletionContextFinder.h"
 #include "swift/Parse/Lexer.h"
+#include "swift/Sema/SyntacticElementTarget.h"
 
 using namespace swift;
+using namespace constraints;
 using Fallback = CompletionContextFinder::Fallback;
 
+CompletionContextFinder::CompletionContextFinder(
+    SyntacticElementTarget target, DeclContext *DC)
+    : InitialExpr(target.getAsExpr()), InitialDC(DC) {
+  assert(DC);
+  target.walk(*this);
+}
+
 ASTWalker::PreWalkResult<Expr *>
 CompletionContextFinder::walkToExprPre(Expr *E) {
   if (auto *closure = dyn_cast<ClosureExpr>(E)) {
diff --git a/lib/Sema/ConstraintLocator.cpp b/lib/Sema/ConstraintLocator.cpp
index e3fe38458601b..4987c3a47cb21 100644
--- a/lib/Sema/ConstraintLocator.cpp
+++ b/lib/Sema/ConstraintLocator.cpp
@@ -90,6 +90,7 @@ unsigned LocatorPathElt::getNewSummaryFlags() const {
   case ConstraintLocator::ImplicitCallAsFunction:
   case ConstraintLocator::TernaryBranch:
   case ConstraintLocator::PatternMatch:
+  case ConstraintLocator::EnumPatternImplicitCastMatch:
   case ConstraintLocator::ArgumentAttribute:
   case ConstraintLocator::UnresolvedMemberChainResult:
   case ConstraintLocator::PlaceholderType:
@@ -403,6 +404,10 @@ void LocatorPathElt::dump(raw_ostream &out) const {
     out << "pattern match";
     break;
 
+  case ConstraintLocator::EnumPatternImplicitCastMatch:
+    out << "enum pattern implicit cast match";
+    break;
+
   case ConstraintLocator::ArgumentAttribute: {
     using AttrLoc = LocatorPathElt::ArgumentAttribute;
 
@@ -677,6 +682,10 @@ NullablePtr<Pattern> ConstraintLocator::getPatternMatch() const {
   return matchElt->getPattern();
 }
 
+bool ConstraintLocator::isForPatternMatch() const {
+  return getPatternMatch() != nullptr;
+}
+
 bool ConstraintLocator::isMemberRef() const {
   if (isLastElement<LocatorPathElt::Member>()) {
     return true;
diff --git a/lib/Sema/ConstraintSystem.cpp b/lib/Sema/ConstraintSystem.cpp
index 36b34ccbd4c84..10563c1fe10f8 100644
--- a/lib/Sema/ConstraintSystem.cpp
+++ b/lib/Sema/ConstraintSystem.cpp
@@ -5824,6 +5824,11 @@ void constraints::simplifyLocator(ASTNode &anchor,
       continue;
     }
 
+    case ConstraintLocator::EnumPatternImplicitCastMatch: {
+      path = path.slice(1);
+      continue;
+    }
+
     case ConstraintLocator::PackType:
     case ConstraintLocator::ParentType:
     case ConstraintLocator::KeyPathType:
diff --git a/lib/Sema/TypeCheckCodeCompletion.cpp b/lib/Sema/TypeCheckCodeCompletion.cpp
index e93d22a6f06ca..58acb0c1e1965 100644
--- a/lib/Sema/TypeCheckCodeCompletion.cpp
+++ b/lib/Sema/TypeCheckCodeCompletion.cpp
@@ -574,15 +574,12 @@ bool TypeChecker::typeCheckForCodeCompletion(
       return false;
   }
 
-  auto node = target.getAsASTNode();
-  if (!node)
-    return false;
-
-  if (auto *expr = getAsExpr(node)) {
-    node = expr->walk(SanitizeExpr(Context));
+  if (getAsExpr(target.getAsASTNode())) {
+    SanitizeExpr sanitizer(Context);
+    target = *target.walk(sanitizer);
   }
 
-  CompletionContextFinder contextAnalyzer(node, DC);
+  CompletionContextFinder contextAnalyzer(target, DC);
 
   // If there was no completion expr (e.g. if the code completion location was
   // among tokens that were skipped over during parser error recovery) bail.
diff --git a/lib/Sema/TypeCheckPattern.cpp b/lib/Sema/TypeCheckPattern.cpp
index 946e86da0d858..69260e9a0975e 100644
--- a/lib/Sema/TypeCheckPattern.cpp
+++ b/lib/Sema/TypeCheckPattern.cpp
@@ -1034,15 +1034,61 @@ void repairTupleOrAssociatedValuePatternIfApplicable(
                 enumCase->getName());
 }
 
+NullablePtr<Pattern> TypeChecker::trySimplifyExprPattern(ExprPattern *EP,
+                                                         Type patternTy) {
+  auto *subExpr = EP->getSubExpr();
+  auto &ctx = EP->getDeclContext()->getASTContext();
+
+  if (patternTy->isBool()) {
+    // The type is Bool.
+    // Check if the pattern is a Bool literal
+    auto *semanticSubExpr = subExpr->getSemanticsProvidingExpr();
+    if (auto *BLE = dyn_cast<BooleanLiteralExpr>(semanticSubExpr)) {
+      auto *BP = new (ctx) BoolPattern(BLE->getLoc(), BLE->getValue());
+      BP->setType(patternTy);
+      return BP;
+    }
+  }
+
+  // case nil is equivalent to .none when switching on Optionals.
+  if (auto *NLE = dyn_cast<NilLiteralExpr>(EP->getSubExpr())) {
+    if (patternTy->getOptionalObjectType()) {
+      auto *NoneEnumElement = ctx.getOptionalNoneDecl();
+      auto *BaseTE = TypeExpr::createImplicit(patternTy, ctx);
+      auto *EEP = new (ctx)
+          EnumElementPattern(BaseTE, NLE->getLoc(), DeclNameLoc(NLE->getLoc()),
+                             NoneEnumElement->createNameRef(), NoneEnumElement,
+                             nullptr, EP->getDeclContext());
+      EEP->setType(patternTy);
+      return EEP;
+    } else {
+      // ...but for non-optional types it can never match! Diagnose it.
+      ctx.Diags
+          .diagnose(NLE->getLoc(), diag::value_type_comparison_with_nil_illegal,
+                    patternTy)
+          .warnUntilSwiftVersion(6);
+
+      if (ctx.isSwiftVersionAtLeast(6))
+        return nullptr;
+    }
+  }
+  return nullptr;
+}
+
 /// Perform top-down type coercion on the given pattern.
-Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
-                                          Type type,
-                                          TypeResolutionOptions options) {
+Pattern *TypeChecker::coercePatternToType(
+    ContextualPattern pattern, Type type, TypeResolutionOptions options,
+    llvm::function_ref<Optional<Pattern *>(Pattern *, Type)>
+        tryRewritePattern) {
   auto P = pattern.getPattern();
   auto dc = pattern.getDeclContext();
   auto &Context = dc->getASTContext();
   auto &diags = Context.Diags;
 
+  // See if we can rewrite this using the constraint system.
+  if (auto result = tryRewritePattern(P, type))
+    return *result;
+
   options = applyContextualPatternOptions(options, pattern);
   auto subOptions = options;
   subOptions.setContext(None);
@@ -1061,8 +1107,8 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
         if (tupleType->getNumElements() == 1) {
           auto element = tupleType->getElement(0);
           sub = coercePatternToType(
-              pattern.forSubPattern(sub, /*retainTopLevel=*/true), element.getType(),
-              subOptions);
+              pattern.forSubPattern(sub, /*retainTopLevel=*/true),
+              element.getType(), subOptions, tryRewritePattern);
           if (!sub)
             return nullptr;
           TuplePatternElt elt(element.getName(), SourceLoc(), sub);
@@ -1077,7 +1123,8 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
     }
 
     sub = coercePatternToType(
-        pattern.forSubPattern(sub, /*retainTopLevel=*/false), type, subOptions);
+        pattern.forSubPattern(sub, /*retainTopLevel=*/false), type, subOptions,
+        tryRewritePattern);
     if (!sub)
       return nullptr;
 
@@ -1090,7 +1137,8 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
 
     Pattern *sub = VP->getSubPattern();
     sub = coercePatternToType(
-        pattern.forSubPattern(sub, /*retainTopLevel=*/false), type, subOptions);
+        pattern.forSubPattern(sub, /*retainTopLevel=*/false), type, subOptions,
+        tryRewritePattern);
     if (!sub)
       return nullptr;
     VP->setSubPattern(sub);
@@ -1123,7 +1171,8 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
     Pattern *sub = TP->getSubPattern();
     sub = coercePatternToType(
         pattern.forSubPattern(sub, /*retainTopLevel=*/false), type,
-        subOptions | TypeResolutionFlags::FromNonInferredPattern);
+        subOptions | TypeResolutionFlags::FromNonInferredPattern,
+        tryRewritePattern);
     if (!sub)
       return nullptr;
 
@@ -1212,9 +1261,9 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
     auto decayToParen = [&]() -> Pattern * {
       assert(canDecayToParen);
       Pattern *sub = TP->getElement(0).getPattern();
-      sub = TypeChecker::coercePatternToType(
+      sub = coercePatternToType(
           pattern.forSubPattern(sub, /*retainTopLevel=*/false), type,
-          subOptions);
+          subOptions, tryRewritePattern);
       if (!sub)
         return nullptr;
 
@@ -1271,7 +1320,7 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
 
       auto sub = coercePatternToType(
           pattern.forSubPattern(elt.getPattern(), /*retainTopLevel=*/false),
-          CoercionType, subOptions);
+          CoercionType, subOptions, tryRewritePattern);
       if (!sub)
         return nullptr;
 
@@ -1291,37 +1340,9 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
     assert(cast<ExprPattern>(P)->isResolved()
            && "coercing unresolved expr pattern!");
     auto *EP = cast<ExprPattern>(P);
-    if (type->isBool()) {
-      // The type is Bool.
-      // Check if the pattern is a Bool literal
-      if (auto *BLE = dyn_cast<BooleanLiteralExpr>(
-              EP->getSubExpr()->getSemanticsProvidingExpr())) {
-        P = new (Context) BoolPattern(BLE->getLoc(), BLE->getValue());
-        P->setType(type);
-        return P;
-      }
-    }
-
-    // case nil is equivalent to .none when switching on Optionals.
-    if (auto *NLE = dyn_cast<NilLiteralExpr>(EP->getSubExpr())) {
-      if (type->getOptionalObjectType()) {
-        auto *NoneEnumElement = Context.getOptionalNoneDecl();
-        auto *BaseTE = TypeExpr::createImplicit(type, Context);
-        P = new (Context) EnumElementPattern(
-            BaseTE, NLE->getLoc(), DeclNameLoc(NLE->getLoc()),
-            NoneEnumElement->createNameRef(), NoneEnumElement, nullptr, dc);
-        return TypeChecker::coercePatternToType(
-            pattern.forSubPattern(P, /*retainTopLevel=*/true), type, options);
-      } else {
-        // ...but for non-optional types it can never match! Diagnose it.
-        diags.diagnose(NLE->getLoc(),
-                       diag::value_type_comparison_with_nil_illegal, type)
-             .warnUntilSwiftVersion(6);
 
-        if (type->getASTContext().isSwiftVersionAtLeast(6))
-          return nullptr;
-      }
-    }
+    if (auto P = trySimplifyExprPattern(EP, type))
+      return P.get();
 
     if (TypeChecker::typeCheckExprPattern(EP, dc, type))
       return nullptr;
@@ -1370,7 +1391,8 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
 
       P = sub;
       return coercePatternToType(
-          pattern.forSubPattern(P, /*retainTopLevel=*/true), type, options);
+          pattern.forSubPattern(P, /*retainTopLevel=*/true), type, options,
+          tryRewritePattern);
     }
 
     CheckedCastKind castKind = TypeChecker::typeCheckCheckedCast(
@@ -1419,7 +1441,8 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
       sub = coercePatternToType(
           pattern.forSubPattern(sub, /*retainTopLevel=*/false),
           IP->getCastType(),
-          subOptions | TypeResolutionFlags::FromNonInferredPattern);
+          subOptions | TypeResolutionFlags::FromNonInferredPattern,
+          tryRewritePattern);
       if (!sub)
         return nullptr;
 
@@ -1457,7 +1480,7 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
                                                       EEP->getEndLoc());
               return coercePatternToType(
                   pattern.forSubPattern(P, /*retainTopLevel=*/true), type,
-                  options);
+                  options, tryRewritePattern);
             } else {
               diags.diagnose(EEP->getLoc(),
                              diag::enum_element_pattern_member_not_found,
@@ -1472,7 +1495,7 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
                 Context, EEP->getUnresolvedOriginalExpr(), dc);
             return coercePatternToType(
                 pattern.forSubPattern(P, /*retainTopLevel=*/true), type,
-                options);
+                options, tryRewritePattern);
           }
         }
       }
@@ -1547,9 +1570,8 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
             type, parentTy, CheckedCastContextKind::EnumElementPattern, dc);
         // If the cast failed, we can't resolve the pattern.
         if (foundCastKind < CheckedCastKind::First_Resolved) {
-          diags
-              .diagnose(EEP->getLoc(), diag::downcast_to_unrelated, type,
-                        parentTy)
+          diags.diagnose(EEP->getLoc(), diag::cannot_match_value_with_pattern,
+                         type, parentTy)
               .highlight(EEP->getSourceRange());
           return nullptr;
         }
@@ -1559,9 +1581,9 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
         castKind = foundCastKind;
         enumTy = parentTy;
       } else {
-        diags.diagnose(EEP->getLoc(),
-                       diag::enum_element_pattern_not_member_of_enum,
-                       EEP->getName(), type);
+        diags.diagnose(EEP->getLoc(), diag::cannot_match_value_with_pattern,
+                       type, parentTy)
+            .highlight(EEP->getSourceRange());
         return nullptr;
       }
     }
@@ -1595,7 +1617,7 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
 
       sub = coercePatternToType(
           pattern.forSubPattern(sub, /*retainTopLevel=*/false), elementType,
-          newSubOptions);
+          newSubOptions, tryRewritePattern);
       if (!sub)
         return nullptr;
 
@@ -1630,7 +1652,7 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
       newSubOptions |= TypeResolutionFlags::FromNonInferredPattern;
       sub = coercePatternToType(
           pattern.forSubPattern(sub, /*retainTopLevel=*/false), elementType,
-          newSubOptions);
+          newSubOptions, tryRewritePattern);
       if (!sub)
         return nullptr;
       EEP->setSubPattern(sub);
@@ -1674,7 +1696,7 @@ Pattern *TypeChecker::coercePatternToType(ContextualPattern pattern,
     newSubOptions |= TypeResolutionFlags::FromNonInferredPattern;
     sub = coercePatternToType(
         pattern.forSubPattern(sub, /*retainTopLevel=*/false), elementType,
-        newSubOptions);
+        newSubOptions, tryRewritePattern);
     if (!sub)
       return nullptr;
 
diff --git a/lib/Sema/TypeChecker.h b/lib/Sema/TypeChecker.h
index 6538ae8cd4f87..4cba8b17db863 100644
--- a/lib/Sema/TypeChecker.h
+++ b/lib/Sema/TypeChecker.h
@@ -733,15 +733,26 @@ Pattern *resolvePattern(Pattern *P, DeclContext *dc, bool isStmtCondition);
 /// unbound generic types.
 Type typeCheckPattern(ContextualPattern pattern);
 
+/// Attempt to simplify an ExprPattern into a BoolPattern or
+/// OptionalSomePattern. Returns \c nullptr if the pattern could not be
+/// simplified.
+NullablePtr<Pattern> trySimplifyExprPattern(ExprPattern *EP, Type patternTy);
+
 /// Coerce a pattern to the given type.
 ///
 /// \param pattern The contextual pattern.
 /// \param type the type to coerce the pattern to.
 /// \param options Options that control the coercion.
+/// \param tryRewritePattern A function that attempts to externally rewrite
+/// the given pattern. This is used by the constraint system to take over
+/// rewriting for ExprPatterns.
 ///
 /// \returns the coerced pattern, or nullptr if the coercion failed.
-Pattern *coercePatternToType(ContextualPattern pattern, Type type,
-                             TypeResolutionOptions options);
+Pattern *coercePatternToType(
+    ContextualPattern pattern, Type type, TypeResolutionOptions options,
+    llvm::function_ref<Optional<Pattern *>(Pattern *, Type)> tryRewritePattern =
+        [](Pattern *, Type) { return None; });
+
 bool typeCheckExprPattern(ExprPattern *EP, DeclContext *DC, Type type);
 
 /// Coerce the specified parameter list of a ClosureExpr to the specified
diff --git a/test/Constraints/patterns.swift b/test/Constraints/patterns.swift
index 0104bbe045c16..7305d549e6fdf 100644
--- a/test/Constraints/patterns.swift
+++ b/test/Constraints/patterns.swift
@@ -120,7 +120,7 @@ case iPadHair<E>.HairForceOne:
   ()
 case iPadHair.HairForceOne: // expected-error{{generic enum type 'iPadHair' is ambiguous without explicit generic parameters when matching value of type 'any HairType'}}
   ()
-case Watch.Edition: // expected-warning {{cast from 'any HairType' to unrelated type 'Watch' always fails}}
+case Watch.Edition: // expected-error {{pattern of type 'Watch' cannot match 'any HairType'}}
   ()
 case .HairForceOne: // expected-error{{type 'any HairType' has no member 'HairForceOne'}}
   ()
@@ -564,3 +564,97 @@ struct TestIUOMatchOp {
     if case self = self {}
   }
 }
+
+struct TestRecursiveVarRef<T> {
+  lazy var e: () -> Int = {e}()
+}
+
+func testMultiStmtClosureExprPattern(_ x: Int) {
+  if case { (); return x }() = x {}
+}
+
+func testExprPatternIsolation() {
+  // We type-check ExprPatterns separately, so these are illegal.
+  if case 0 = nil {} // expected-error {{'nil' requires a contextual type}}
+  let _ = {
+    if case 0 = nil {} // expected-error {{'nil' requires a contextual type}}
+  }
+  for case 0 in nil {} // expected-error {{'nil' requires a contextual type}}
+  for case 0 in [nil] {}
+  // expected-error@-1 {{type 'Any' cannot conform to 'Equatable'}}
+  // expected-note@-2 {{only concrete types such as structs, enums and classes can conform to protocols}}
+  // expected-note@-3 {{requirement from conditional conformance of 'Any?' to 'Equatable'}}
+
+  // Though we will try Double for an integer literal...
+  let d: Double = 0
+  if case d = 0 {}
+  let _ = {
+    if case d = 0 {}
+  }
+  for case d in [0] {}
+
+  // But not Float
+  let f: Float = 0
+  if case f = 0 {} // expected-error {{expression pattern of type 'Float' cannot match values of type 'Int'}}
+  let _ = {
+    if case f = 0 {} // expected-error {{expression pattern of type 'Float' cannot match values of type 'Int'}}
+  }
+  for case f in [0] {}  // expected-error {{expression pattern of type 'Float' cannot match values of type 'Int'}}
+
+  enum MultiPayload<T: Equatable>: Equatable {
+    case e(T, T)
+    static func f(_ x: T, _ y: T) -> Self { .e(x, y) }
+  }
+  enum E: Equatable {
+    case a, b
+    static var c: E { .a }
+    static var d: E { .b }
+  }
+
+  func produceMultiPayload<T>() -> MultiPayload<T> { fatalError() }
+
+  // We type-check ExprPatterns left to right, so only one of these works.
+  if case .e(0.0, 0) = produceMultiPayload() {}
+  if case .e(0, 0.0) = produceMultiPayload() {} // expected-error {{expression pattern of type 'Double' cannot match values of type 'Int'}}
+
+  for case .e(0.0, 0) in [produceMultiPayload()] {}
+  for case .e(0, 0.0) in [produceMultiPayload()] {} // expected-error {{expression pattern of type 'Double' cannot match values of type 'Int'}}
+
+  // Same, because although it's a top-level ExprPattern, we don't resolve
+  // that until during solving.
+  if case .f(0.0, 0) = produceMultiPayload() {}
+  if case .f(0, 0.0) = produceMultiPayload() {} // expected-error {{expression pattern of type 'Double' cannot match values of type 'Int'}}
+
+  if case .e(5, nil) = produceMultiPayload() {} // expected-warning {{type 'Int' is not optional, value can never be nil; this is an error in Swift 6}}
+
+  // FIXME: Bad error (https://github.com/apple/swift/issues/64279)
+  if case .e(nil, 0) = produceMultiPayload() {}
+  // expected-error@-1 {{expression pattern of type 'String' cannot match values of type 'Substring'}}
+  // expected-note@-2 {{overloads for '~=' exist with these partially matching parameter lists}}
+
+  if case .e(5, nil) = produceMultiPayload() as MultiPayload<Int?> {}
+  if case .e(nil, 0) = produceMultiPayload() as MultiPayload<Int?> {}
+
+  // Enum patterns are solved together.
+  if case .e(E.a, .b) = produceMultiPayload() {}
+  if case .e(.a, E.b) = produceMultiPayload() {}
+
+  // These also work because they start life as EnumPatterns.
+  if case .e(E.c, .d) = produceMultiPayload() {}
+  if case .e(.c, E.d) = produceMultiPayload() {}
+  for case .e(E.c, .d) in [produceMultiPayload()] {}
+  for case .e(.c, E.d) in [produceMultiPayload()] {}
+
+  // Silly, but allowed.
+  if case 0: Int? = 0 {} // expected-warning {{non-optional expression of type 'Int' used in a check for optionals}}
+
+  var opt: Int?
+  if case opt = 0 {}
+}
+
+enum LotsOfOptional {
+  case yup(Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?)
+}
+func testLotsOfNil(_ x: LotsOfOptional) {
+  if case .yup(nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil) = x {}
+}
diff --git a/test/Constraints/rdar105781521.swift b/test/Constraints/rdar105781521.swift
index ec76bf061d662..6e5f6eebe3092 100644
--- a/test/Constraints/rdar105781521.swift
+++ b/test/Constraints/rdar105781521.swift
@@ -12,7 +12,6 @@ func test(value: MyEnum) {
     switch value {
     case .first(true):
       // expected-error@-1 {{expression pattern of type 'Bool' cannot match values of type 'String'}}
-      // expected-note@-2 {{overloads for '~=' exist with these partially matching parameter lists: (Substring, String)}}
       break
     default:
       break
diff --git a/test/Constraints/rdar105782480.swift b/test/Constraints/rdar105782480.swift
new file mode 100644
index 0000000000000..581f7b3d0db3b
--- /dev/null
+++ b/test/Constraints/rdar105782480.swift
@@ -0,0 +1,18 @@
+// RUN: %target-typecheck-verify-swift
+
+// rdar://105782480
+enum MyEnum {
+  case second(Int?)
+}
+
+func takeClosure(_ x: () -> Void) {}
+
+func foo(value: MyEnum) {
+  takeClosure {
+    switch value {
+    case .second(let drag).invalid:
+      // expected-error@-1 {{value of type 'MyEnum' has no member 'invalid'}}
+      break
+    }
+  }
+}
diff --git a/test/Constraints/rdar106598067.swift b/test/Constraints/rdar106598067.swift
new file mode 100644
index 0000000000000..941bbae2f2a2e
--- /dev/null
+++ b/test/Constraints/rdar106598067.swift
@@ -0,0 +1,11 @@
+// RUN: %target-typecheck-verify-swift
+
+enum E: Error { case e }
+
+// rdar://106598067 – Make sure we don't crash.
+// FIXME: Bad diagnostic (the issue is that it should be written 'as', not 'as?')
+let fn = {
+  // expected-error@-1 {{unable to infer closure type in the current context}}
+  do {} catch let x as? E {}
+  // expected-warning@-1 {{'catch' block is unreachable because no errors are thrown in 'do' block}}
+}
diff --git a/test/Constraints/rdar107420031.swift b/test/Constraints/rdar107420031.swift
new file mode 100644
index 0000000000000..2f5687eb6fe31
--- /dev/null
+++ b/test/Constraints/rdar107420031.swift
@@ -0,0 +1,18 @@
+// RUN: %target-typecheck-verify-swift
+
+enum E {
+  case e
+}
+
+func ~= (lhs: any Error, rhs: E) -> Bool { true }
+
+// rdar://107420031 – Make sure we don't crash.
+// TODO: This ought to compile.
+func foo(_ error: any Error) {
+  switch error {
+  case E.e: // expected-error {{pattern of type 'E' cannot match 'any Error'}}
+    break
+  default:
+    break
+  }
+}
diff --git a/test/Constraints/rdar107709341.swift b/test/Constraints/rdar107709341.swift
new file mode 100644
index 0000000000000..cc38962ec4f12
--- /dev/null
+++ b/test/Constraints/rdar107709341.swift
@@ -0,0 +1,13 @@
+// RUN: %target-typecheck-verify-swift
+
+// rdar://107709341 – Make sure we don't crash.
+func foo(_ x: Int) {
+  let _ = {
+    switch x {
+    case Optional<Int>.some(x): // expected-error {{pattern of type 'Optional<Int>' cannot match 'Int'}} {{none}}
+      break
+    default:
+      break
+    }
+  }
+}
diff --git a/test/Constraints/rdar109419240.swift b/test/Constraints/rdar109419240.swift
new file mode 100644
index 0000000000000..9d78a4c6cf831
--- /dev/null
+++ b/test/Constraints/rdar109419240.swift
@@ -0,0 +1,15 @@
+// RUN: %target-typecheck-verify-swift
+
+// rdar://109419240 – Make sure we don't crash
+enum E { // expected-note {{'E' declared here}}
+  case e(Int)
+}
+
+func foo(_ arr: [E]) -> Int {
+  return arr.reduce(0) { (total, elem) -> Int in
+    switch elem {
+    case let e(x): // expected-error {{cannot find 'e' in scope; did you mean 'E'?}}
+      return total + x
+    }
+  }
+}
diff --git a/test/Constraints/result_builder_diags.swift b/test/Constraints/result_builder_diags.swift
index 660e719a0e569..5cd49c0cc771a 100644
--- a/test/Constraints/result_builder_diags.swift
+++ b/test/Constraints/result_builder_diags.swift
@@ -659,8 +659,6 @@ struct MyView {
   }
 
   @TupleBuilder var invalidCaseWithoutDot: some P {
-  // expected-error@-1 {{return type of property 'invalidCaseWithoutDot' requires that 'Either<Int, Int>' conform to 'P'}}
-  // expected-note@-2 {{opaque return type declared here}}
     switch Optional.some(1) {
     case none: 42 // expected-error {{cannot find 'none' in scope}}
     case .some(let x):
diff --git a/test/Constraints/result_builder_invalid_stmts.swift b/test/Constraints/result_builder_invalid_stmts.swift
index 5de3ccc668b1f..5f8dc47268ee4 100644
--- a/test/Constraints/result_builder_invalid_stmts.swift
+++ b/test/Constraints/result_builder_invalid_stmts.swift
@@ -15,7 +15,6 @@ func foo(_ x: String) -> Int {
   if .random() {
     switch x {
     case 1: // expected-error {{expression pattern of type 'Int' cannot match values of type 'String'}}
-      // expected-note@-1 {{overloads for '~=' exist with these partially matching parameter lists}}
       0
     default:
       1
@@ -29,7 +28,6 @@ func bar(_ x: String) -> Int {
   case 0:
     switch x {
     case 1: // expected-error {{expression pattern of type 'Int' cannot match values of type 'String'}}
-    // expected-note@-1 {{overloads for '~=' exist with these partially matching parameter lists}}
       0
     default:
       1
@@ -44,7 +42,6 @@ func baz(_ x: String) -> Int {
   do {
     switch x {
     case 1: // expected-error {{expression pattern of type 'Int' cannot match values of type 'String'}}
-    // expected-note@-1 {{overloads for '~=' exist with these partially matching parameter lists}}
       0
     default:
       1
@@ -57,7 +54,6 @@ func qux(_ x: String) -> Int {
   for _ in 0 ... 0 {
     switch x {
     case 1: // expected-error {{expression pattern of type 'Int' cannot match values of type 'String'}}
-    // expected-note@-1 {{overloads for '~=' exist with these partially matching parameter lists}}
       0
     default:
       1
diff --git a/test/IDE/complete_unresolved_members.swift b/test/IDE/complete_unresolved_members.swift
index 0e29f7935297e..f81f9a6c31ade 100644
--- a/test/IDE/complete_unresolved_members.swift
+++ b/test/IDE/complete_unresolved_members.swift
@@ -710,3 +710,38 @@ let _: DispatchTime = .#^UNRESOLVED_FUNCTION_CALL^#now() + 0.2
 // UNRESOLVED_FUNCTION_CALL: Begin completions, 2 items
 // UNRESOLVED_FUNCTION_CALL-DAG: Decl[StaticMethod]/CurrNominal/Flair[ExprSpecific]/TypeRelation[Convertible]: now()[#DispatchTime#];
 // UNRESOLVED_FUNCTION_CALL-DAG: Decl[Constructor]/CurrNominal/TypeRelation[Convertible]: init()[#DispatchTime#];
+
+func id<T>(_ x: T) -> T { x }
+
+func testNestedExprPatternCompletion(_ x: SomeEnum1) {
+  // Multi-statement closures have different type-checking code paths,
+  // so we need to test both.
+  let fn = {
+    switch x {
+    case id(.#^UNRESOLVED_NESTED1^#):
+      // UNRESOLVED_NESTED1: Begin completions, 3 items
+      // UNRESOLVED_NESTED1: Decl[EnumElement]/CurrNominal/Flair[ExprSpecific]/TypeRelation[Convertible]: South[#SomeEnum1#]; name=South
+      // UNRESOLVED_NESTED1: Decl[EnumElement]/CurrNominal/Flair[ExprSpecific]/TypeRelation[Convertible]: North[#SomeEnum1#]; name=North
+      // UNRESOLVED_NESTED1: Decl[InstanceMethod]/CurrNominal/TypeRelation[Invalid]: hash({#(self): SomeEnum1#})[#(into: inout Hasher) -> Void#]; name=hash(:)
+      break
+    }
+    if case id(.#^UNRESOLVED_NESTED2^#) = x {}
+    // UNRESOLVED_NESTED2: Begin completions, 3 items
+    // UNRESOLVED_NESTED2: Decl[EnumElement]/CurrNominal/Flair[ExprSpecific]/TypeRelation[Convertible]: South[#SomeEnum1#]; name=South
+    // UNRESOLVED_NESTED2: Decl[EnumElement]/CurrNominal/Flair[ExprSpecific]/TypeRelation[Convertible]: North[#SomeEnum1#]; name=North
+    // UNRESOLVED_NESTED2: Decl[InstanceMethod]/CurrNominal/TypeRelation[Invalid]: hash({#(self): SomeEnum1#})[#(into: inout Hasher) -> Void#]; name=hash(:)
+  }
+  switch x {
+  case id(.#^UNRESOLVED_NESTED3^#):
+    // UNRESOLVED_NESTED3: Begin completions, 3 items
+    // UNRESOLVED_NESTED3: Decl[EnumElement]/CurrNominal/Flair[ExprSpecific]/TypeRelation[Convertible]: South[#SomeEnum1#]; name=South
+    // UNRESOLVED_NESTED3: Decl[EnumElement]/CurrNominal/Flair[ExprSpecific]/TypeRelation[Convertible]: North[#SomeEnum1#]; name=North
+    // UNRESOLVED_NESTED3: Decl[InstanceMethod]/CurrNominal/TypeRelation[Invalid]: hash({#(self): SomeEnum1#})[#(into: inout Hasher) -> Void#]; name=hash(:)
+    break
+  }
+  if case id(.#^UNRESOLVED_NESTED4^#) = x {}
+  // UNRESOLVED_NESTED4: Begin completions, 3 items
+  // UNRESOLVED_NESTED4: Decl[EnumElement]/CurrNominal/Flair[ExprSpecific]/TypeRelation[Convertible]: South[#SomeEnum1#]; name=South
+  // UNRESOLVED_NESTED4: Decl[EnumElement]/CurrNominal/Flair[ExprSpecific]/TypeRelation[Convertible]: North[#SomeEnum1#]; name=North
+  // UNRESOLVED_NESTED4: Decl[InstanceMethod]/CurrNominal/TypeRelation[Invalid]: hash({#(self): SomeEnum1#})[#(into: inout Hasher) -> Void#]; name=hash(:)
+}
diff --git a/test/Parse/matching_patterns.swift b/test/Parse/matching_patterns.swift
index 932fb84e550c8..050916fac0574 100644
--- a/test/Parse/matching_patterns.swift
+++ b/test/Parse/matching_patterns.swift
@@ -122,7 +122,7 @@ if case let .Naught(value1, value2, value3) = n {} // expected-error{{pattern wi
 
 
 switch n {
-case Foo.A: // expected-error{{enum case 'A' is not a member of type 'Voluntary<Int>'}}
+case Foo.A: // expected-error{{pattern of type 'Foo' cannot match 'Voluntary<Int>'}}
   ()
 case Voluntary<Int>.Naught,
      Voluntary<Int>.Naught(), // expected-error {{pattern with associated values does not match enum case 'Naught'}}
@@ -307,6 +307,7 @@ do {
   while case let _ as [Derived] = arr {}
   // expected-warning@-1 {{'let' pattern has no effect; sub-pattern didn't bind any variables}}
 
+  // https://github.com/apple/swift/issues/61850
   for case _ as [Derived] in [arr] {}
 
   if case is [Derived] = arr {}
diff --git a/test/Parse/matching_patterns_reference_bindings.swift b/test/Parse/matching_patterns_reference_bindings.swift
index 906bea74dfae0..fbf6b9840b1b2 100644
--- a/test/Parse/matching_patterns_reference_bindings.swift
+++ b/test/Parse/matching_patterns_reference_bindings.swift
@@ -140,7 +140,7 @@ if case inout .Naught(value1, value2, value3) = n {} // expected-error{{pattern
 
 
 switch n {
-case Foo.A: // expected-error{{enum case 'A' is not a member of type 'Voluntary<Int>'}}
+case Foo.A: // expected-error{{pattern of type 'Foo' cannot match 'Voluntary<Int>'}}
   ()
 case Voluntary<Int>.Naught,
      Voluntary<Int>.Naught(), // expected-error {{pattern with associated values does not match enum case 'Naught'}}
@@ -328,6 +328,7 @@ do {
   while case let _ as [Derived] = arr {}
   // expected-warning@-1 {{'let' pattern has no effect; sub-pattern didn't bind any variables}}
 
+  // https://github.com/apple/swift/issues/61850
   for case _ as [Derived] in [arr] {}
 
   if case is [Derived] = arr {}
diff --git a/test/SILGen/switch_expr.swift b/test/SILGen/switch_expr.swift
index 7275aa1bb534d..310dc90329ab3 100644
--- a/test/SILGen/switch_expr.swift
+++ b/test/SILGen/switch_expr.swift
@@ -605,3 +605,14 @@ struct TestLValues {
     opt![keyPath: kp] = switch Bool.random() { case true: 1 case false: throw Err() }
   }
 }
+
+func exprPatternInClosure() {
+  let f: (Int) -> Void = { i in
+    switch i {
+    case i:
+      ()
+    default:
+      ()
+    }
+  }
+}
diff --git a/test/decl/var/property_wrappers.swift b/test/decl/var/property_wrappers.swift
index fa33d07393543..33acdbf13df9a 100644
--- a/test/decl/var/property_wrappers.swift
+++ b/test/decl/var/property_wrappers.swift
@@ -1338,7 +1338,7 @@ struct MissingPropertyWrapperUnwrap {
 
 struct InvalidPropertyDelegateUse {
   // TODO(diagnostics): We need to a tailored diagnostic for extraneous arguments in property delegate initialization
-  @Foo var x: Int = 42 // expected-error@:21 {{argument passed to call that takes no arguments}}
+  @Foo var x: Int = 42 // expected-error@:21 {{extra argument 'wrappedValue' in call}}
 
   func test() {
     self.x.foo() // expected-error {{value of type 'Int' has no member 'foo'}}
diff --git a/test/stdlib/StringDiagnostics.swift b/test/stdlib/StringDiagnostics.swift
index c3fde8ff884f5..3a53a26c69ee0 100644
--- a/test/stdlib/StringDiagnostics.swift
+++ b/test/stdlib/StringDiagnostics.swift
@@ -48,7 +48,6 @@ func testAmbiguousStringComparisons(s: String) {
   
   // Shouldn't suggest 'as' in a pattern-matching context, as opposed to all these other situations
   if case nsString = "" {} // expected-error{{expression pattern of type 'NSString' cannot match values of type 'String'}}
-  // expected-note@-1 {{overloads for '~=' exist with these partially matching parameter lists: (Substring, String)}}
 }
 
 func testStringDeprecation(hello: String) {
diff --git a/test/stmt/errors.swift b/test/stmt/errors.swift
index d71da201b4247..506b2230f775a 100644
--- a/test/stmt/errors.swift
+++ b/test/stmt/errors.swift
@@ -169,7 +169,8 @@ func thirteen() {
   thirteen_helper { (a) in // expected-error {{invalid conversion from throwing function of type '(Thirteen) throws -> ()' to non-throwing function type '(Thirteen) -> ()'}}
     do {
       try thrower()
-    } catch a {
+      // FIXME: Bad diagnostic (https://github.com/apple/swift/issues/63459)
+    } catch a { // expected-error {{binary operator '~=' cannot be applied to two 'any Error' operands}}
     }
   }
 }
diff --git a/validation-test/Sema/SwiftUI/rdar70256351.swift b/validation-test/Sema/SwiftUI/rdar70256351.swift
index 0881009bd7457..1aa7ad723e977 100644
--- a/validation-test/Sema/SwiftUI/rdar70256351.swift
+++ b/validation-test/Sema/SwiftUI/rdar70256351.swift
@@ -10,7 +10,6 @@ struct ContentView: View {
   var body: some View {
     switch currentPage {
     case 1: // expected-error {{expression pattern of type 'Int' cannot match values of type 'String'}}
-            // expected-note@-1 {{overloads for '~=' exist with these partially matching parameter lists: (Substring, String)}}
       Text("1")
     default:
       Text("default")
diff --git a/validation-test/Sema/type_checker_crashers_fixed/issue-65360.swift b/validation-test/Sema/type_checker_crashers_fixed/issue-65360.swift
index 2e7e10322c932..fd6652a85f4e4 100644
--- a/validation-test/Sema/type_checker_crashers_fixed/issue-65360.swift
+++ b/validation-test/Sema/type_checker_crashers_fixed/issue-65360.swift
@@ -9,12 +9,24 @@ let _: () -> Void = {
 
 let _: () -> Void = {
   for case (0)? in [a] {}
+  // expected-error@-1 {{pattern cannot match values of type 'Any?'}}
   if case (0, 0) = a {}
-  // expected-error@-1 {{cannot convert value of type 'Any?' to specified type '(_, _)}}
 }
 
 let _: () -> Void = {
   for case (0)? in [a] {}
+  // expected-error@-1 {{pattern cannot match values of type 'Any?'}}
   for case (0, 0) in [a] {}
-  // expected-error@-1 {{cannot convert value of type 'Any?' to expected element type '(_, _)'}}
+}
+
+let _: () -> Void = {
+  if case (0, 0) = a {}
+  // expected-error@-1 {{cannot convert value of type 'Any?' to specified type '(Int, Int)'}}
+  for case (0)? in [a] {}
+}
+
+let _: () -> Void = {
+  for case (0, 0) in [a] {}
+  // expected-error@-1 {{cannot convert value of type 'Any?' to expected element type '(Int, Int)'}}
+  for case (0)? in [a] {}
 }