Merge pull request dotnet#49154 from huoyaoyuan/issue-48742

Don't generate nullable type when applying value type with unconstrained nullable generic
cston · May 17, 2021 · ac43b83 · ac43b83
2 parents 6c46bd0 + 3638c73
commit ac43b83
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Showing 2 changed files with 137 additions and 3 deletions.
diff --git a/src/EditorFeatures/CSharpTest/ImplementAbstractClass/ImplementAbstractClassTests.cs b/src/EditorFeatures/CSharpTest/ImplementAbstractClass/ImplementAbstractClassTests.cs
@@ -1911,5 +1911,134 @@ public override void AbstractMethod()
     }
 }", parseOptions: TestOptions.RegularPreview);
         }
+
+        [WorkItem(48742, "https://github.com/dotnet/roslyn/issues/48742")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsImplementAbstractClass)]
+        public async Task TestUnconstrainedGenericNullable()
+        {
+            await TestAllOptionsOffAsync(
+@"#nullable enable
+
+abstract class B<T>
+{
+    public abstract T? M();
+}
+
+class [|D|] : B<int>
+{
+}",
+@"#nullable enable
+
+abstract class B<T>
+{
+    public abstract T? M();
+}
+
+class D : B<int>
+{
+    public override int M()
+    {
+        throw new System.NotImplementedException();
+    }
+}");
+        }
+
+        [WorkItem(48742, "https://github.com/dotnet/roslyn/issues/48742")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsImplementAbstractClass)]
+        public async Task TestUnconstrainedGenericNullable2()
+        {
+            await TestAllOptionsOffAsync(
+@"#nullable enable
+
+abstract class B<T>
+{
+    public abstract T? M();
+}
+
+class [|D<T>|] : B<T> where T : struct
+{
+}",
+@"#nullable enable
+
+abstract class B<T>
+{
+    public abstract T? M();
+}
+
+class D<T> : B<T> where T : struct
+{
+    public override T M()
+    {
+        throw new System.NotImplementedException();
+    }
+}");
+        }
+
+        [WorkItem(48742, "https://github.com/dotnet/roslyn/issues/48742")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsImplementAbstractClass)]
+        public async Task TestUnconstrainedGenericNullable_Tuple()
+        {
+            await TestAllOptionsOffAsync(
+@"#nullable enable
+
+abstract class B<T>
+{
+    public abstract T? M();
+}
+
+class [|D<T>|] : B<(T, T)>
+{
+}",
+@"#nullable enable
+
+abstract class B<T>
+{
+    public abstract T? M();
+}
+
+class D<T> : B<(T, T)>
+{
+    public override (T, T) M()
+    {
+        throw new System.NotImplementedException();
+    }
+}");
+        }
+
+        [WorkItem(48742, "https://github.com/dotnet/roslyn/issues/48742")]
+        [Theory, Trait(Traits.Feature, Traits.Features.CodeActionsImplementAbstractClass)]
+        [InlineData("", "T")]
+        [InlineData(" where T : class", "T")]
+        [InlineData("", "T?")]
+        [InlineData(" where T : class", "T?")]
+        [InlineData(" where T : struct", "T?")]
+        public async Task TestUnconstrainedGenericNullable_NoRegression(string constraint, string passToBase)
+        {
+            await TestAllOptionsOffAsync(
+$@"#nullable enable
+
+abstract class B<T>
+{{
+    public abstract T? M();
+}}
+
+class [|D<T>|] : B<{passToBase}>{constraint}
+{{
+}}",
+$@"#nullable enable
+
+abstract class B<T>
+{{
+    public abstract T? M();
+}}
+
+class D<T> : B<{passToBase}>{constraint}
+{{
+    public override T? M()
+    {{
+        throw new System.NotImplementedException();
+    }}
+}}");
+        }
     }
 }
diff --git a/...xtensions/Workspace/CSharp/Extensions/ITypeSymbolExtensions.TypeSyntaxGeneratorVisitor.cs b/...xtensions/Workspace/CSharp/Extensions/ITypeSymbolExtensions.TypeSyntaxGeneratorVisitor.cs
@@ -300,9 +300,10 @@ public override TypeSyntax VisitNamedType(INamedTypeSymbol symbol)
                     }
                 }
 
-                if (symbol.NullableAnnotation == NullableAnnotation.Annotated &&
-                    !symbol.IsValueType)
+                if (symbol is { IsValueType: false, NullableAnnotation: NullableAnnotation.Annotated })
                 {
+                    // value type with nullable annotation may be composed from unconstrained nullable generic
+                    // doesn't mean nullable value type in this case
                     typeSyntax = AddInformationTo(SyntaxFactory.NullableType(typeSyntax), symbol);
                 }
 
@@ -355,8 +356,12 @@ public override TypeSyntax VisitPointerType(IPointerTypeSymbol symbol)
             public override TypeSyntax VisitTypeParameter(ITypeParameterSymbol symbol)
             {
                 TypeSyntax typeSyntax = AddInformationTo(symbol.Name.ToIdentifierName(), symbol);
-                if (symbol.NullableAnnotation == NullableAnnotation.Annotated)
+                if (symbol is { IsValueType: false, NullableAnnotation: NullableAnnotation.Annotated })
+                {
+                    // value type with nullable annotation may be composed from unconstrained nullable generic
+                    // doesn't mean nullable value type in this case
                     typeSyntax = AddInformationTo(SyntaxFactory.NullableType(typeSyntax), symbol);
+                }
 
                 return typeSyntax;
             }