diff --git a/compiler/ast.nim b/compiler/ast.nim
index 9679c10c12791..198d21bead807 100644
--- a/compiler/ast.nim
+++ b/compiler/ast.nim
@@ -2047,6 +2047,9 @@ template detailedInfo*(sym: PSym): string =
 proc isInlineIterator*(typ: PType): bool {.inline.} =
   typ.kind == tyProc and tfIterator in typ.flags and typ.callConv != ccClosure
 
+proc isIterator*(typ: PType): bool {.inline.} =
+  typ.kind == tyProc and tfIterator in typ.flags
+
 proc isClosureIterator*(typ: PType): bool {.inline.} =
   typ.kind == tyProc and tfIterator in typ.flags and typ.callConv == ccClosure
 
diff --git a/compiler/docgen.nim b/compiler/docgen.nim
index e2c04430c4152..0a24d2e095ce1 100644
--- a/compiler/docgen.nim
+++ b/compiler/docgen.nim
@@ -558,7 +558,7 @@ proc runAllExamples(d: PDoc) =
 
 proc quoted(a: string): string = result.addQuoted(a)
 
-proc toInstantiationInfo(conf: ConfigRef, info: TLineInfo): auto =
+proc toInstantiationInfo(conf: ConfigRef, info: TLineInfo): (string, int, int) =
   # xxx expose in compiler/lineinfos.nim
   (conf.toMsgFilename(info), info.line.int, info.col.int + ColOffset)
 
diff --git a/compiler/lookups.nim b/compiler/lookups.nim
index 2121982a6594b..df5a5333e92a9 100644
--- a/compiler/lookups.nim
+++ b/compiler/lookups.nim
@@ -422,7 +422,7 @@ type SpellCandidate = object
   msg: string
   sym: PSym
 
-template toOrderTup(a: SpellCandidate): auto =
+template toOrderTup(a: SpellCandidate): (int, int, string) =
   # `dist` is first, to favor nearby matches
   # `depth` is next, to favor nearby enclosing scopes among ties
   # `sym.name.s` is last, to make the list ordered and deterministic among ties
diff --git a/compiler/sem.nim b/compiler/sem.nim
index a1388bd877e2d..1f8e217b335d8 100644
--- a/compiler/sem.nim
+++ b/compiler/sem.nim
@@ -81,7 +81,7 @@ template semIdeForTemplateOrGeneric(c: PContext; n: PNode;
 proc fitNodePostMatch(c: PContext, formal: PType, arg: PNode): PNode =
   let x = arg.skipConv
   if (x.kind == nkCurly and formal.kind == tySet and formal.base.kind != tyGenericParam) or
-    (x.kind in {nkPar, nkTupleConstr}) and formal.kind notin {tyUntyped, tyBuiltInTypeClass}:
+    (x.kind in {nkPar, nkTupleConstr}) and formal.kind notin {tyUntyped, tyBuiltInTypeClass, tyAnything}:
     changeType(c, x, formal, check=true)
   result = arg
   result = skipHiddenSubConv(result, c.graph, c.idgen)
@@ -439,7 +439,7 @@ proc semAfterMacroCall(c: PContext, call, macroResult: PNode,
       # does not mean we expect a tyTypeDesc.
       retType = retType[0]
     case retType.kind
-    of tyUntyped:
+    of tyUntyped, tyAnything:
       # Not expecting a type here allows templates like in ``tmodulealias.in``.
       result = semExpr(c, result, flags, expectedType)
     of tyTyped:
diff --git a/compiler/semexprs.nim b/compiler/semexprs.nim
index 064eae0b716d0..2efa1259a890a 100644
--- a/compiler/semexprs.nim
+++ b/compiler/semexprs.nim
@@ -1843,6 +1843,8 @@ proc semAsgn(c: PContext, n: PNode; mode=asgnNormal): PNode =
         var rhsTyp = rhs.typ
         if rhsTyp.kind in tyUserTypeClasses and rhsTyp.isResolvedUserTypeClass:
           rhsTyp = rhsTyp.lastSon
+        if lhs.sym.typ.kind == tyAnything:
+          rhsTyp = rhsTyp.skipIntLit(c.idgen)
         if cmpTypes(c, lhs.typ, rhsTyp) in {isGeneric, isEqual}:
           internalAssert c.config, c.p.resultSym != nil
           # Make sure the type is valid for the result variable
@@ -1916,8 +1918,8 @@ proc semProcBody(c: PContext, n: PNode; expectedType: PType = nil): PNode =
     else:
       localError(c.config, c.p.resultSym.info, errCannotInferReturnType %
         c.p.owner.name.s)
-  if isInlineIterator(c.p.owner.typ) and c.p.owner.typ[0] != nil and
-      c.p.owner.typ[0].kind == tyUntyped:
+  if isIterator(c.p.owner.typ) and c.p.owner.typ[0] != nil and
+      c.p.owner.typ[0].kind == tyAnything:
     localError(c.config, c.p.owner.info, errCannotInferReturnType %
       c.p.owner.name.s)
   closeScope(c)
diff --git a/compiler/semstmts.nim b/compiler/semstmts.nim
index a006013b805f2..d19d75611a015 100644
--- a/compiler/semstmts.nim
+++ b/compiler/semstmts.nim
@@ -2179,8 +2179,7 @@ proc semProcAux(c: PContext, n: PNode, kind: TSymKind,
     if hasProto: localError(c.config, n.info, errImplOfXexpected % proto.name.s)
     if {sfImportc, sfBorrow, sfError} * s.flags == {} and s.magic == mNone:
       # this is a forward declaration and we're building the prototype
-      if s.kind in {skProc, skFunc} and s.typ[0] != nil and s.typ[0].kind == tyUntyped:
-        # `auto` is represented as `tyUntyped` at this point in compilation.
+      if s.kind in {skProc, skFunc} and s.typ[0] != nil and s.typ[0].kind == tyAnything:
         localError(c.config, n[paramsPos][0].info, "return type 'auto' cannot be used in forward declarations")
 
       incl(s.flags, sfForward)
diff --git a/compiler/semtypes.nim b/compiler/semtypes.nim
index 3eaf297556bb8..dca0d753b79c4 100644
--- a/compiler/semtypes.nim
+++ b/compiler/semtypes.nim
@@ -1405,9 +1405,7 @@ proc semProcTypeNode(c: PContext, n, genericParams: PNode,
             "' is only valid for macros and templates")
       # 'auto' as a return type does not imply a generic:
       elif r.kind == tyAnything:
-        # 'p(): auto' and 'p(): untyped' are equivalent, but the rest of the
-        # compiler is hardly aware of 'auto':
-        r = newTypeS(tyUntyped, c)
+        discard
       elif r.kind == tyStatic:
         # type allowed should forbid this type
         discard
diff --git a/tests/misc/t12869.nim b/tests/misc/t12869.nim
new file mode 100644
index 0000000000000..731a4e95ec586
--- /dev/null
+++ b/tests/misc/t12869.nim
@@ -0,0 +1,14 @@
+discard """
+  errormsg: "type mismatch: got <bool> but expected 'int'"
+  line: 12
+"""
+
+import sugar
+from algorithm import sorted, SortOrder
+
+let a = 5
+
+proc sorted*[T](a: openArray[T], key: proc(v: T): int, order = SortOrder.Ascending): seq[T] =
+  sorted(a, (x, y) => key(x) < key(y), order)
+
+echo sorted(@[9, 1, 8, 2, 6, 4, 5, 0], (x) => (a - x).abs)
diff --git a/tests/misc/t16244.nim b/tests/misc/t16244.nim
new file mode 100644
index 0000000000000..5e81287369e80
--- /dev/null
+++ b/tests/misc/t16244.nim
@@ -0,0 +1,9 @@
+discard """
+  errormsg: "type mismatch: got <int, float64>"
+  line: 9
+"""
+
+proc g(): auto = 1
+proc h(): auto = 1.0
+
+var a = g() + h()
diff --git a/tests/proc/tillegalreturntype.nim b/tests/proc/tillegalreturntype.nim
index 799cad53a6ca7..1076f7f75ce17 100644
--- a/tests/proc/tillegalreturntype.nim
+++ b/tests/proc/tillegalreturntype.nim
@@ -1,5 +1,5 @@
 discard """
-  cmd: "nim check $file"
+  cmd: "nim check --hints:off $file"
   errormsg: ""
   nimout: '''
 tillegalreturntype.nim(11, 11) Error: return type 'typed' is only valid for macros and templates
diff --git a/tests/types/t15836.nim b/tests/types/t15836.nim
new file mode 100644
index 0000000000000..9c0c26decf084
--- /dev/null
+++ b/tests/types/t15836.nim
@@ -0,0 +1,11 @@
+discard """
+  errormsg: "type mismatch: got <string> but expected 'int'"
+  line: 11
+""" 
+
+proc takesProc[T](x: T, f: proc(x: T): int) =
+    echo f(x) + 2
+
+takesProc(1, proc (a: int): int = 2) # ok, prints 4
+takesProc(1, proc (a: auto): auto = 2) # ok, prints 4
+takesProc(1, proc (a: auto): auto = "uh uh") # prints garbage
diff --git a/tests/types/t15836_2.nim b/tests/types/t15836_2.nim
new file mode 100644
index 0000000000000..9afef416a88db
--- /dev/null
+++ b/tests/types/t15836_2.nim
@@ -0,0 +1,26 @@
+
+discard """
+  action: "compile"
+  disabled: true
+"""
+import std/sugar
+
+type Tensor[T] = object
+  x: T
+
+proc numerical_gradient*[T](input: T, f: (proc(x: T): T), h = T(1e-5)): T {.inline.} =
+  result = default(T)
+
+proc numerical_gradient*[T](input: Tensor[T], f: (proc(x: Tensor[T]): T), h = T(1e-5)): Tensor[T] {.noinit.} =
+  result = default(Tensor[T])
+
+proc conv2d*[T](input: Tensor[T]): Tensor[T] {.inline.} =
+  result = default(Tensor[T])
+
+proc sum*[T](arg: Tensor[T]): T = default(T)
+
+proc sum*[T](arg: Tensor[T], axis: int): Tensor[T] {.noinit.} = default(Tensor[T])
+
+let dinput = Tensor[int](x: 1)
+let target_grad_input = dinput.numerical_gradient(
+    x => conv2d(x).sum())