Create returnOnlySignature only when inferences will possibly be made

Author: ahejlsberg

src/compiler/checker.ts

@@ -26051,15 +26051,19 @@ namespace ts {
             if (checkMode && checkMode & CheckMode.SkipContextSensitive && isContextSensitive(node)) {
                 // Skip parameters, return signature with return type that retains noncontextual parts so inferences can still be drawn in an early stage
                 if (!getEffectiveReturnTypeNode(node) && hasContextSensitiveReturnExpression(node)) {
-                    const links = getNodeLinks(node);
-                    if (links.contextFreeType) {
-                        return links.contextFreeType;
-                    }
-                    const returnType = getReturnTypeFromBody(node, checkMode);
-                    const returnOnlySignature = createSignature(undefined, undefined, undefined, emptyArray, returnType, /*resolvedTypePredicate*/ undefined, 0, SignatureFlags.None);
-                    const returnOnlyType = createAnonymousType(node.symbol, emptySymbols, [returnOnlySignature], emptyArray, undefined, undefined);
-                    returnOnlyType.objectFlags |= ObjectFlags.NonInferrableType;
-                    return links.contextFreeType = returnOnlyType;
+                    // Return plain anyFunctionType if there is no possibility we'll make inferences from the return type
+                    const contextualSignature = getContextualSignature(node);
+                    if (contextualSignature && couldContainTypeVariables(getReturnTypeOfSignature(contextualSignature))) {
+                        const links = getNodeLinks(node);
+                        if (links.contextFreeType) {
+                            return links.contextFreeType;
+                        }
+                        const returnType = getReturnTypeFromBody(node, checkMode);
+                        const returnOnlySignature = createSignature(undefined, undefined, undefined, emptyArray, returnType, /*resolvedTypePredicate*/ undefined, 0, SignatureFlags.None);
+                        const returnOnlyType = createAnonymousType(node.symbol, emptySymbols, [returnOnlySignature], emptyArray, undefined, undefined);
+                        returnOnlyType.objectFlags |= ObjectFlags.NonInferrableType;
+                        return links.contextFreeType = returnOnlyType;
+                    }
                 }
                 return anyFunctionType;
             }