BoundUsingLocalDeclarations/BoundUsingStatement - don't store Conversion in the node.

src/Compilers/CSharp/Portable/Binder/UsingStatementBinder.cs

@@ -100,7 +100,6 @@ internal static BoundStatement BindUsingStatementOrDeclarationFromParts(SyntaxNo
             Debug.Assert((object)disposableInterface != null);
             bool hasErrors = ReportUseSite(disposableInterface, diagnostics, hasAwait ? awaitKeyword : usingKeyword);
 
-            Conversion iDisposableConversion;
             ImmutableArray<BoundLocalDeclaration> declarationsOpt = default;
             BoundMultipleLocalDeclarations? multipleDeclarationsOpt = null;
             BoundExpression? expressionOpt = null;
@@ -111,7 +110,7 @@ internal static BoundStatement BindUsingStatementOrDeclarationFromParts(SyntaxNo
             if (isExpression)
             {
                 expressionOpt = usingBinderOpt!.BindTargetExpression(diagnostics, originalBinder);
-                hasErrors |= !populateDisposableConversionOrDisposeMethod(fromExpression: true, out iDisposableConversion, out patternDisposeInfo, out awaitableTypeOpt);
+                hasErrors |= !bindDisposable(fromExpression: true, out patternDisposeInfo, out awaitableTypeOpt);
             }
             else
             {
@@ -124,13 +123,12 @@ internal static BoundStatement BindUsingStatementOrDeclarationFromParts(SyntaxNo
 
                 if (declarationTypeOpt.IsDynamic())
                 {
-                    iDisposableConversion = Conversion.ImplicitDynamic;
                     patternDisposeInfo = null;
                     awaitableTypeOpt = null;
                 }
                 else
                 {
-                    hasErrors |= !populateDisposableConversionOrDisposeMethod(fromExpression: false, out iDisposableConversion, out patternDisposeInfo, out awaitableTypeOpt);
+                    hasErrors |= !bindDisposable(fromExpression: false, out patternDisposeInfo, out awaitableTypeOpt);
                 }
             }
 
@@ -156,7 +154,7 @@ internal static BoundStatement BindUsingStatementOrDeclarationFromParts(SyntaxNo
             // In the future it might be better to have a separate shared type that we add the info to, and have the callers create the appropriate bound nodes from it
             if (isUsingDeclaration)
             {
-                return new BoundUsingLocalDeclarations(syntax, patternDisposeInfo, iDisposableConversion, awaitOpt, declarationsOpt, hasErrors);
+                return new BoundUsingLocalDeclarations(syntax, patternDisposeInfo, awaitOpt, declarationsOpt, hasErrors);
             }
             else
             {
@@ -167,17 +165,16 @@ internal static BoundStatement BindUsingStatementOrDeclarationFromParts(SyntaxNo
                     usingBinderOpt.Locals,
                     multipleDeclarationsOpt,
                     expressionOpt,
-                    iDisposableConversion,
                     boundBody,
                     awaitOpt,
                     patternDisposeInfo,
                     hasErrors);
             }
 
-            bool populateDisposableConversionOrDisposeMethod(bool fromExpression, out Conversion iDisposableConversion, out MethodArgumentInfo? patternDisposeInfo, out TypeSymbol? awaitableType)
+            bool bindDisposable(bool fromExpression, out MethodArgumentInfo? patternDisposeInfo, out TypeSymbol? awaitableType)
             {
                 CompoundUseSiteInfo<AssemblySymbol> useSiteInfo = originalBinder.GetNewCompoundUseSiteInfo(diagnostics);
-                iDisposableConversion = classifyConversion(fromExpression, disposableInterface, ref useSiteInfo);
+                Conversion iDisposableConversion = classifyConversion(fromExpression, disposableInterface, ref useSiteInfo);
                 patternDisposeInfo = null;
                 awaitableType = null;
 
@@ -261,12 +258,18 @@ Conversion classifyConversion(bool fromExpression, TypeSymbol targetInterface, r
                 if (fromExpression)
                 {
                     Debug.Assert(expressionOpt is { });
-                    return conversions.ClassifyImplicitConversionFromExpression(expressionOpt, targetInterface, ref useSiteInfo);
+                    var result = conversions.ClassifyImplicitConversionFromExpression(expressionOpt, targetInterface, ref useSiteInfo);
+
+                    Debug.Assert(expressionOpt.Type?.IsDynamic() != true || result.Kind == ConversionKind.ImplicitDynamic);
+                    return result;
                 }
                 else
                 {
                     Debug.Assert(declarationTypeOpt is { });
-                    return conversions.ClassifyImplicitConversionFromType(declarationTypeOpt, targetInterface, ref useSiteInfo);
+                    var result = conversions.ClassifyImplicitConversionFromType(declarationTypeOpt, targetInterface, ref useSiteInfo);
+
+                    Debug.Assert(!declarationTypeOpt.IsDynamic() || result.Kind == ConversionKind.ImplicitDynamic);
+                    return result;
                 }
             }
 

src/Compilers/CSharp/Portable/BoundTree/BoundNodes.xml

@@ -933,7 +933,6 @@
   -->
   <Node Name="BoundUsingLocalDeclarations" Base="BoundMultipleLocalDeclarationsBase">
     <Field Name="PatternDisposeInfoOpt" Type="MethodArgumentInfo?"/>
-    <Field Name="IDisposableConversion" Type="Conversion"/>
     <Field Name="AwaitOpt" Type="BoundAwaitableInfo?"/>
   </Node>
 
@@ -1099,7 +1098,6 @@
     <Field Name="Locals" Type="ImmutableArray&lt;LocalSymbol&gt;"/>
     <Field Name="DeclarationsOpt" Type="BoundMultipleLocalDeclarations?"/>
     <Field Name="ExpressionOpt" Type="BoundExpression?"/>
-    <Field Name="IDisposableConversion" Type="Conversion" />
     <Field Name="Body" Type="BoundStatement"/>
     <Field Name="AwaitOpt" Type="BoundAwaitableInfo?"/>
     <Field Name="PatternDisposeInfoOpt" Type="MethodArgumentInfo?"/>

src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_UsingStatement.cs

@@ -52,7 +52,6 @@ public override BoundNode VisitUsingStatement(BoundUsingStatement node)
                                                      tryBlock,
                                                      node.Locals,
                                                      node.DeclarationsOpt.LocalDeclarations,
-                                                     node.IDisposableConversion,
                                                      node.PatternDisposeInfoOpt,
                                                      node.AwaitOpt,
                                                      awaitKeyword);
@@ -63,7 +62,6 @@ private BoundStatement MakeDeclarationUsingStatement(SyntaxNode syntax,
                                                        BoundBlock body,
                                                        ImmutableArray<LocalSymbol> locals,
                                                        ImmutableArray<BoundLocalDeclaration> declarations,
-                                                       Conversion iDisposableConversion,
                                                        MethodArgumentInfo? patternDisposeInfo,
                                                        BoundAwaitableInfo? awaitOpt,
                                                        SyntaxToken awaitKeyword)
@@ -73,7 +71,7 @@ private BoundStatement MakeDeclarationUsingStatement(SyntaxNode syntax,
             BoundBlock result = body;
             for (int i = declarations.Length - 1; i >= 0; i--) //NB: inner-to-outer = right-to-left
             {
-                result = RewriteDeclarationUsingStatement(syntax, declarations[i], result, iDisposableConversion, awaitKeyword, awaitOpt, patternDisposeInfo);
+                result = RewriteDeclarationUsingStatement(syntax, declarations[i], result, awaitKeyword, awaitOpt, patternDisposeInfo);
             }
 
             // Declare all locals in a single, top-level block so that the scope is correct in the debugger
@@ -96,7 +94,6 @@ private BoundStatement MakeLocalUsingDeclarationStatement(BoundUsingLocalDeclara
                                                                body,
                                                                ImmutableArray<LocalSymbol>.Empty,
                                                                usingDeclarations.LocalDeclarations,
-                                                               usingDeclarations.IDisposableConversion,
                                                                usingDeclarations.PatternDisposeInfoOpt,
                                                                awaitOpt: usingDeclarations.AwaitOpt,
                                                                awaitKeyword: syntax.AwaitKeyword);
@@ -155,7 +152,8 @@ private BoundBlock MakeExpressionUsingStatement(BoundUsingStatement node, BoundB
 
             BoundAssignmentOperator tempAssignment;
             BoundLocal boundTemp;
-            if (expressionType is null || expressionType.IsDynamic())
+
+            if (expressionType.IsDynamic())
             {
                 // IDisposable temp = (IDisposable) expr;
                 // or
@@ -169,7 +167,7 @@ private BoundBlock MakeExpressionUsingStatement(BoundUsingStatement node, BoundB
                 BoundExpression tempInit = MakeConversionNode(
                     expressionSyntax,
                     rewrittenExpression,
-                    Conversion.GetTrivialConversion(node.IDisposableConversion.Kind),
+                    Conversion.ImplicitDynamic,
                     iDisposableType,
                     @checked: false,
                     constantValueOpt: rewrittenExpression.ConstantValue);
@@ -208,7 +206,6 @@ private BoundBlock RewriteDeclarationUsingStatement(
             SyntaxNode usingSyntax,
             BoundLocalDeclaration localDeclaration,
             BoundBlock tryBlock,
-            Conversion iDisposableConversion,
             SyntaxToken awaitKeywordOpt,
             BoundAwaitableInfo? awaitOpt,
             MethodArgumentInfo? patternDisposeInfo)
@@ -246,7 +243,7 @@ private BoundBlock RewriteDeclarationUsingStatement(
                 BoundExpression tempInit = MakeConversionNode(
                     declarationSyntax,
                     boundLocal,
-                    iDisposableConversion,
+                    Conversion.ImplicitDynamic,
                     iDisposableType,
                     @checked: false);