Suggest completions of property values in type arguments

Author: mkantor

src/services/completions.ts

@@ -3625,17 +3625,20 @@ function getCompletionData(
     }
 
     log("getCompletionData: Semantic work: " + (timestamp() - semanticStart));
-    const contextualType = previousToken && getContextualType(previousToken, position, sourceFile, typeChecker);
+    const contextualTypeOrConstraint = previousToken && (
+        getContextualType(previousToken, position, sourceFile, typeChecker) ??
+            getConstraintOfTypeArgumentProperty(previousToken, typeChecker)
+    );
 
     // exclude literal suggestions after <input type="text" [||] /> (#51667) and after closing quote (#52675)
     // for strings getStringLiteralCompletions handles completions
     const isLiteralExpected = !tryCast(previousToken, isStringLiteralLike) && !isJsxIdentifierExpected;
     const literals = !isLiteralExpected ? [] : mapDefined(
-        contextualType && (contextualType.isUnion() ? contextualType.types : [contextualType]),
+        contextualTypeOrConstraint && (contextualTypeOrConstraint.isUnion() ? contextualTypeOrConstraint.types : [contextualTypeOrConstraint]),
         t => t.isLiteral() && !(t.flags & TypeFlags.EnumLiteral) ? t.value : undefined,
     );
 
-    const recommendedCompletion = previousToken && contextualType && getRecommendedCompletion(previousToken, contextualType, typeChecker);
+    const recommendedCompletion = previousToken && contextualTypeOrConstraint && getRecommendedCompletion(previousToken, contextualTypeOrConstraint, typeChecker);
     return {
         kind: CompletionDataKind.Data,
         symbols,
@@ -5779,6 +5782,13 @@ function getConstraintOfTypeArgumentProperty(node: Node, checker: TypeChecker):
     switch (node.kind) {
         case SyntaxKind.PropertySignature:
             return checker.getTypeOfPropertyOfContextualType(t, (node as PropertySignature).symbol.escapedName);
+        case SyntaxKind.ColonToken:
+            if (node.parent.kind === SyntaxKind.PropertySignature) {
+                // The cursor is at a property value location like `Foo<{ x: | }`.
+                // `t` already refers to the appropriate property type.
+                return t;
+            }
+            break;
         case SyntaxKind.IntersectionType:
         case SyntaxKind.TypeLiteral:
         case SyntaxKind.UnionType:

tests/cases/fourslash/completionListInTypeLiteralInTypeParameter17.ts

@@ -0,0 +1,18 @@
+/// <reference path="fourslash.ts" />
+
+////class Foo<T extends { x: 'one' | 2 }> {}
+////function foo<T extends { x: 'one' | 2 }>() {}
+////
+////type A = Foo<{ x: /*0*/ }>;
+////new Foo<{ x: /*1*/ }>();
+////foo<{ x: /*2*/ }>();
+////foo<{ x: /*3*/ }>;
+////Foo<{ x: /*4*/ }>;
+
+verify.completions(
+    { marker: "0", includes: ['"one"', '2'], isNewIdentifierLocation: false },
+    { marker: "1", includes: ['"one"', '2'], isNewIdentifierLocation: false },
+    { marker: "2", includes: ['"one"', '2'], isNewIdentifierLocation: false },
+    { marker: "3", includes: ['"one"', '2'], isNewIdentifierLocation: false },
+    { marker: "4", includes: ['"one"', '2'], isNewIdentifierLocation: false },
+);