Clarify error message when an accessor is invoked.

Author: krk

src/compiler/checker.ts

@@ -20061,13 +20061,47 @@ namespace ts {
                 }
                 else {
                     let relatedInformation: DiagnosticRelatedInformation | undefined;
+                    let propertyName: string | undefined;
+                    let propertyAccessorText: string | undefined;
                     if (node.arguments.length === 1 && isTypeAssertion(first(node.arguments))) {
                         const text = getSourceFileOfNode(node).text;
                         if (isLineBreak(text.charCodeAt(skipTrivia(text, node.expression.end, /* stopAfterLineBreak */ true) - 1))) {
                             relatedInformation = createDiagnosticForNode(node.expression, Diagnostics.It_is_highly_likely_that_you_are_missing_a_semicolon);
                         }
                     }
-                    invocationError(node, apparentType, SignatureKind.Call, relatedInformation);
+                    else if (node.expression.kind === SyntaxKind.PropertyAccessExpression) {
+                        const propertyAccess = node.expression as PropertyAccessExpression;
+                        const symbol = getSymbolOfEntityNameOrPropertyAccessExpression(propertyAccess);
+
+                        // Handle union types with non-function-like signatures.
+                        if (symbol) {
+                            const links = getSymbolLinks(symbol);
+                            const isObjectUnionOrIntersection = links && links.type && (
+                                (links.type.flags & (TypeFlags.Union | TypeFlags.Intersection | TypeFlags.Object)) !== 0
+                            ) || false;
+
+                            let invokable = isObjectUnionOrIntersection;
+                            if (isObjectUnionOrIntersection) {
+                                if (links && links.type && (links.type.flags & TypeFlags.Object)) {
+                                    const resolvedType = links.type as ObjectType;
+                                    invokable = (resolvedType.callSignatures && resolvedType.callSignatures.length !== 0) || false;
+                                }
+                                else {
+                                    const resolvedType = links.type as UnionOrIntersectionType;
+                                    invokable = every(resolvedType.types, ty => (ty as ResolvedType).callSignatures && (ty as ResolvedType).callSignatures.length !== 0);
+                                }
+                            }
+
+                            if (!invokable) {
+                                const file = getSourceFileOfNode(node);
+
+                                propertyName = propertyAccess.name.escapedText.toString();
+                                propertyAccessorText = createPrinter().printNode(EmitHint.Expression, propertyAccess, file);
+                            }
+                        }
+                    }
+
+                    invocationError(node, apparentType, SignatureKind.Call, relatedInformation, propertyName, propertyAccessorText);
                 }
                 return resolveErrorCall(node);
             }
@@ -20237,11 +20271,14 @@ namespace ts {
             return true;
         }
 
-        function invocationError(node: Node, apparentType: Type, kind: SignatureKind, relatedInformation?: DiagnosticRelatedInformation) {
+        function invocationError(node: Node, apparentType: Type, kind: SignatureKind, relatedInformation?: DiagnosticRelatedInformation, propertyName?: string, didYouMean?: string) {
             const diagnostic = error(node, (kind === SignatureKind.Call ?
-                Diagnostics.Cannot_invoke_an_expression_whose_type_lacks_a_call_signature_Type_0_has_no_compatible_call_signatures :
+                (propertyName === undefined ?
+                    Diagnostics.Cannot_invoke_an_expression_whose_type_lacks_a_call_signature_Type_0_has_no_compatible_call_signatures :
+                    Diagnostics.Cannot_invoke_expression_1_which_is_a_property_and_has_the_type_0_which_has_no_compatible_call_signature_Did_you_mean_2
+                    ) :
                 Diagnostics.Cannot_use_new_with_an_expression_whose_type_lacks_a_call_or_construct_signature
-            ), typeToString(apparentType));
+            ), typeToString(apparentType), propertyName, didYouMean);
             invocationErrorRecovery(apparentType, kind, relatedInformation ? addRelatedInfo(diagnostic, relatedInformation) : diagnostic);
         }
 

src/compiler/diagnosticMessages.json

@@ -2489,6 +2489,10 @@
         "category": "Error",
         "code": 2734
     },
+    "Cannot invoke expression `{1}`, which is a property and has the type `{0}` which has no compatible call signature. Did you mean `{2}`": {
+        "category": "Error",
+        "code": 2735
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",

tests/baselines/reference/instancePropertiesInheritedIntoClassType.errors.txt

@@ -1,9 +1,9 @@
 tests/cases/conformance/classes/members/classTypes/instancePropertiesInheritedIntoClassType.ts(4,13): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
 tests/cases/conformance/classes/members/classTypes/instancePropertiesInheritedIntoClassType.ts(7,13): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/conformance/classes/members/classTypes/instancePropertiesInheritedIntoClassType.ts(19,14): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'Number' has no compatible call signatures.
+tests/cases/conformance/classes/members/classTypes/instancePropertiesInheritedIntoClassType.ts(19,14): error TS2735: Cannot invoke expression `y`, which is a property and has the type `Number` which has no compatible call signature. Did you mean `d.y`
 tests/cases/conformance/classes/members/classTypes/instancePropertiesInheritedIntoClassType.ts(26,13): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
 tests/cases/conformance/classes/members/classTypes/instancePropertiesInheritedIntoClassType.ts(29,13): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/conformance/classes/members/classTypes/instancePropertiesInheritedIntoClassType.ts(41,14): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+tests/cases/conformance/classes/members/classTypes/instancePropertiesInheritedIntoClassType.ts(41,14): error TS2735: Cannot invoke expression `y`, which is a property and has the type `String` which has no compatible call signature. Did you mean `d.y`
 
 
 ==== tests/cases/conformance/classes/members/classTypes/instancePropertiesInheritedIntoClassType.ts (6 errors) ====
@@ -31,7 +31,7 @@ tests/cases/conformance/classes/members/classTypes/instancePropertiesInheritedIn
         r.y = 4;
         var r6 = d.y(); // error
                  ~~~~~
-!!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'Number' has no compatible call signatures.
+!!! error TS2735: Cannot invoke expression `y`, which is a property and has the type `Number` which has no compatible call signature. Did you mean `d.y`
 
     }
 
@@ -59,5 +59,5 @@ tests/cases/conformance/classes/members/classTypes/instancePropertiesInheritedIn
         r.y = '';
         var r6 = d.y(); // error
                  ~~~~~
-!!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+!!! error TS2735: Cannot invoke expression `y`, which is a property and has the type `String` which has no compatible call signature. Did you mean `d.y`
     }

tests/baselines/reference/instancePropertyInClassType.errors.txt

@@ -1,9 +1,9 @@
 tests/cases/conformance/classes/members/classTypes/instancePropertyInClassType.ts(4,13): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
 tests/cases/conformance/classes/members/classTypes/instancePropertyInClassType.ts(7,13): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/conformance/classes/members/classTypes/instancePropertyInClassType.ts(17,14): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'Number' has no compatible call signatures.
+tests/cases/conformance/classes/members/classTypes/instancePropertyInClassType.ts(17,14): error TS2735: Cannot invoke expression `y`, which is a property and has the type `Number` which has no compatible call signature. Did you mean `c.y`
 tests/cases/conformance/classes/members/classTypes/instancePropertyInClassType.ts(24,13): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
 tests/cases/conformance/classes/members/classTypes/instancePropertyInClassType.ts(27,13): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/conformance/classes/members/classTypes/instancePropertyInClassType.ts(37,14): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+tests/cases/conformance/classes/members/classTypes/instancePropertyInClassType.ts(37,14): error TS2735: Cannot invoke expression `y`, which is a property and has the type `String` which has no compatible call signature. Did you mean `c.y`
 
 
 ==== tests/cases/conformance/classes/members/classTypes/instancePropertyInClassType.ts (6 errors) ====
@@ -29,7 +29,7 @@ tests/cases/conformance/classes/members/classTypes/instancePropertyInClassType.t
         r.y = 4;
         var r6 = c.y(); // error
                  ~~~~~
-!!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'Number' has no compatible call signatures.
+!!! error TS2735: Cannot invoke expression `y`, which is a property and has the type `Number` which has no compatible call signature. Did you mean `c.y`
 
     }
 
@@ -55,5 +55,5 @@ tests/cases/conformance/classes/members/classTypes/instancePropertyInClassType.t
         r.y = '';
         var r6 = c.y(); // error
                  ~~~~~
-!!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+!!! error TS2735: Cannot invoke expression `y`, which is a property and has the type `String` which has no compatible call signature. Did you mean `c.y`
     }