Nullable analysis of yield return (#31072)

dotnet · Nov 13, 2018 · ff8e1c7 · ff8e1c7
1 parent c4598d7
commit ff8e1c7
Show file tree

Hide file tree

Showing 6 changed files with 752 additions and 273 deletions.
diff --git a/src/Compilers/CSharp/Portable/Binder/InMethodBinder.cs b/src/Compilers/CSharp/Portable/Binder/InMethodBinder.cs
@@ -176,27 +176,37 @@ internal override TypeSymbol GetIteratorElementType(YieldStatementSyntax node, D
         }
 
         private TypeSymbol GetIteratorElementTypeFromReturnType(RefKind refKind, TypeSymbol returnType, CSharpSyntaxNode errorLocationNode, DiagnosticBag diagnostics)
+        {
+            return GetIteratorElementTypeFromReturnType(Compilation, refKind, returnType, errorLocationNode, diagnostics).TypeSymbol;
+        }
+
+        internal static TypeSymbolWithAnnotations GetIteratorElementTypeFromReturnType(CSharpCompilation compilation, RefKind refKind, TypeSymbol returnType, CSharpSyntaxNode errorLocationNode, DiagnosticBag diagnostics)
         {
             if (refKind == RefKind.None && returnType.Kind == SymbolKind.NamedType)
             {
                 switch (returnType.OriginalDefinition.SpecialType)
                 {
                     case SpecialType.System_Collections_IEnumerable:
                     case SpecialType.System_Collections_IEnumerator:
-                        return GetSpecialType(SpecialType.System_Object, diagnostics, errorLocationNode);
+                        var objectType = compilation.GetSpecialType(SpecialType.System_Object);
+                        if (diagnostics != null)
+                        {
+                            ReportUseSiteDiagnostics(objectType, diagnostics, errorLocationNode);
+                        }
+                        return TypeSymbolWithAnnotations.Create(objectType);
 
                     case SpecialType.System_Collections_Generic_IEnumerable_T:
                     case SpecialType.System_Collections_Generic_IEnumerator_T:
-                        return ((NamedTypeSymbol)returnType).TypeArgumentsNoUseSiteDiagnostics[0].TypeSymbol;
+                        return ((NamedTypeSymbol)returnType).TypeArgumentsNoUseSiteDiagnostics[0];
                 }
 
-                if (returnType.OriginalDefinition == Compilation.GetWellKnownType(WellKnownType.System_Collections_Generic_IAsyncEnumerable_T))
+                if (returnType.OriginalDefinition == compilation.GetWellKnownType(WellKnownType.System_Collections_Generic_IAsyncEnumerable_T))
                 {
-                    return ((NamedTypeSymbol)returnType).TypeArgumentsNoUseSiteDiagnostics[0].TypeSymbol;
+                    return ((NamedTypeSymbol)returnType).TypeArgumentsNoUseSiteDiagnostics[0];
                 }
             }
 
-            return null;
+            return default;
         }
 
         internal override void LookupSymbolsInSingleBinder(

diff --git a/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs b/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs
@@ -4592,6 +4592,19 @@ public override BoundNode VisitThrowExpression(BoundThrowExpression node)
             return result;
         }
 
+        public override BoundNode VisitYieldReturnStatement(BoundYieldReturnStatement node)
+        {
+            BoundExpression expr = node.Expression;
+            if (expr == null)
+            {
+                return null;
+            }
+            var method = (MethodSymbol)_member;
+            TypeSymbolWithAnnotations elementType = InMethodBinder.GetIteratorElementTypeFromReturnType(compilation, RefKind.None, method.ReturnType.TypeSymbol, errorLocationNode: null, diagnostics: null);
+            VisitOptionalImplicitConversion(expr, elementType, useLegacyWarnings: false, AssignmentKind.Return);
+            return null;
+        }
+
 #endregion Visitors
 
         protected override string Dump(LocalState state)