Merge pull request #14320 from AlekseyTs/Issue5002

SymbolDisplayVisitor.CreateAliasMap – pop out of speculative semantic model to lookup for declared aliases.

src/Compilers/CSharp/Portable/SymbolDisplay/SymbolDisplayVisitor_Minimal.cs

@@ -166,7 +166,22 @@ private void MinimallyQualify(INamedTypeSymbol symbol)
                 return SpecializedCollections.EmptyDictionary<INamespaceOrTypeSymbol, IAliasSymbol>();
             }
 
-            var token = semanticModelOpt.SyntaxTree.GetRoot().FindToken(positionOpt);
+            // Walk up the ancestors from the current position. If this is a speculative
+            // model, walk up the corresponding ancestors in the parent model.
+            SemanticModel semanticModel;
+            int position;
+            if (semanticModelOpt.IsSpeculativeSemanticModel)
+            {
+                semanticModel = semanticModelOpt.ParentModel;
+                position = semanticModelOpt.OriginalPositionForSpeculation;
+            }
+            else
+            {
+                semanticModel = semanticModelOpt;
+                position = positionOpt;
+            }
+ 
+            var token = semanticModel.SyntaxTree.GetRoot().FindToken(position);
             var startNode = token.Parent;
 
             // NOTE(cyrusn): If we're currently in a block of usings, then we want to collect the
@@ -182,7 +197,7 @@ private void MinimallyQualify(INamedTypeSymbol symbol)
                 .SelectMany(n => n.Usings)
                 .Concat(GetAncestorsOrThis<CompilationUnitSyntax>(startNode).SelectMany(c => c.Usings))
                 .Where(u => u.Alias != null)
-                .Select(u => semanticModelOpt.GetDeclaredSymbol(u) as IAliasSymbol)
+                .Select(u => semanticModel.GetDeclaredSymbol(u) as IAliasSymbol)
                 .Where(u => u != null);
 
             var builder = ImmutableDictionary.CreateBuilder<INamespaceOrTypeSymbol, IAliasSymbol>();

src/Compilers/CSharp/Test/Symbol/SymbolDisplay/SymbolDisplayTests.cs

@@ -7,6 +7,7 @@
 using System.Linq;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Symbols;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
 using Microsoft.CodeAnalysis.Test.Utilities;
 using Roslyn.Test.Utilities;
@@ -5182,5 +5183,44 @@ public void DisplayFakeTupleTypeSymbol()
                 SymbolDisplayPartKind.Keyword, // string
                 SymbolDisplayPartKind.Punctuation);
         }
+
+        [WorkItem(5002, "https://github.com/dotnet/roslyn/issues/5002")]
+        [Fact]
+        public void AliasInSpeculativeSemanticModel()
+        {
+            var text =
+@"using A = N.M;
+namespace N.M
+{
+    class B
+    {
+    }
+}
+class C
+{
+    static void M()
+    {
+    }
+}";
+            var comp = CreateCompilationWithMscorlib(text);
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+            var methodDecl = tree.GetCompilationUnitRoot().DescendantNodes().OfType<MethodDeclarationSyntax>().First();
+            int position = methodDecl.Body.SpanStart;
+
+            tree = CSharpSyntaxTree.ParseText(@"
+class C
+{
+    static void M()
+    {
+    }
+}");
+            methodDecl = tree.GetCompilationUnitRoot().DescendantNodes().OfType<MethodDeclarationSyntax>().First();
+            Assert.True(model.TryGetSpeculativeSemanticModelForMethodBody(position, methodDecl, out model));
+            var symbol = comp.GetMember<NamedTypeSymbol>("N.M.B");
+            position = methodDecl.Body.SpanStart;
+            var description = symbol.ToMinimalDisplayParts(model, position, SymbolDisplayFormat.MinimallyQualifiedFormat);
+            Verify(description, "A.B", SymbolDisplayPartKind.AliasName, SymbolDisplayPartKind.Punctuation, SymbolDisplayPartKind.ClassName);
+        }
     }
 }

src/Compilers/VisualBasic/Test/Symbol/SymbolDisplay/SymbolDisplayTests.vb

@@ -4603,6 +4603,42 @@ class Outer
             Assert.Equal(Nothing, SymbolDisplay.FormatPrimitive(New Object(), quoteStrings:=False, useHexadecimalNumbers:=False))
         End Sub
 
+        <Fact>
+        Public Sub AliasInSpeculativeSemanticModel()
+            Dim text =
+        <compilation>
+            <file name="a.vb">
+Imports A = N.M
+Namespace N.M
+    Class B
+    End Class
+End Namespace
+Class C
+    Shared Sub M()
+        Dim o = 1
+    End Sub
+End Class
+                </file>
+        </compilation>
+            Dim comp = CompilationUtils.CreateCompilationWithMscorlib(text)
+            Dim tree = comp.SyntaxTrees.First()
+            Dim model = comp.GetSemanticModel(tree)
+            Dim methodDecl = tree.GetCompilationUnitRoot().DescendantNodes().OfType(Of MethodBlockBaseSyntax)().First()
+            Dim position = methodDecl.Statements(0).SpanStart
+            tree = VisualBasicSyntaxTree.ParseText("
+Class C
+    Shared Sub M()
+        Dim o = 1
+    End Sub
+End Class")
+            methodDecl = tree.GetCompilationUnitRoot().DescendantNodes().OfType(Of MethodBlockBaseSyntax)().First()
+            Assert.True(model.TryGetSpeculativeSemanticModelForMethodBody(position, methodDecl, model))
+            Dim symbol = comp.GetMember(Of NamedTypeSymbol)("N.M.B")
+            position = methodDecl.Statements(0).SpanStart
+            Dim description = symbol.ToMinimalDisplayParts(model, position, SymbolDisplayFormat.MinimallyQualifiedFormat)
+            Verify(description, "A.B", SymbolDisplayPartKind.AliasName, SymbolDisplayPartKind.Operator, SymbolDisplayPartKind.ClassName)
+        End Sub
+
 #Region "Helpers"
 
         Private Sub TestSymbolDescription(