Better error message for accidental calls to get-accessors

src/compiler/checker.ts

@@ -26383,7 +26383,7 @@ namespace ts {
             return true;
         }
 
-        function invocationErrorDetails(apparentType: Type, kind: SignatureKind): { messageChain: DiagnosticMessageChain, relatedMessage: DiagnosticMessage | undefined } {
+        function invocationErrorDetails(errorTarget: Node, apparentType: Type, kind: SignatureKind): { messageChain: DiagnosticMessageChain, relatedMessage: DiagnosticMessage | undefined } {
             let errorInfo: DiagnosticMessageChain | undefined;
             const isCall = kind === SignatureKind.Call;
             const awaitedType = getAwaitedType(apparentType);
@@ -26452,16 +26452,24 @@ namespace ts {
                     typeToString(apparentType)
                 );
             }
+
+            let headMessage = isCall ? Diagnostics.This_expression_is_not_callable : Diagnostics.This_expression_is_not_constructable;
+
+            // Diagnose get accessors incorrectly called as functions
+            if (isCallExpression(errorTarget.parent) && errorTarget.parent.arguments.length === 0) {
+                const { resolvedSymbol } = getNodeLinks(errorTarget);
+                if (resolvedSymbol && resolvedSymbol.flags & SymbolFlags.GetAccessor) {
+                    headMessage = Diagnostics.This_expression_is_not_callable_because_it_is_a_get_accessor_Did_you_mean_to_use_it_without;
+                }
+            }
+
             return {
-                messageChain: chainDiagnosticMessages(
-                    errorInfo,
-                    isCall ? Diagnostics.This_expression_is_not_callable : Diagnostics.This_expression_is_not_constructable
-                ),
+                messageChain: chainDiagnosticMessages(errorInfo, headMessage),
                 relatedMessage: maybeMissingAwait ? Diagnostics.Did_you_forget_to_use_await : undefined,
             };
         }
         function invocationError(errorTarget: Node, apparentType: Type, kind: SignatureKind, relatedInformation?: DiagnosticRelatedInformation) {
-            const { messageChain, relatedMessage: relatedInfo } = invocationErrorDetails(apparentType, kind);
+            const { messageChain, relatedMessage: relatedInfo } = invocationErrorDetails(errorTarget, apparentType, kind);
             const diagnostic = createDiagnosticForNodeFromMessageChain(errorTarget, messageChain);
             if (relatedInfo) {
                 addRelatedInfo(diagnostic, createDiagnosticForNode(errorTarget, relatedInfo));
@@ -26565,7 +26573,7 @@ namespace ts {
 
             const headMessage = getDiagnosticHeadMessageForDecoratorResolution(node);
             if (!callSignatures.length) {
-                const errorDetails = invocationErrorDetails(apparentType, SignatureKind.Call);
+                const errorDetails = invocationErrorDetails(node.expression, apparentType, SignatureKind.Call);
                 const messageChain = chainDiagnosticMessages(errorDetails.messageChain, headMessage);
                 const diag = createDiagnosticForNodeFromMessageChain(node.expression, messageChain);
                 if (errorDetails.relatedMessage) {

src/compiler/diagnosticMessages.json

@@ -4416,6 +4416,10 @@
         "category": "Error",
         "code": 6233
     },
+    "This expression is not callable because it is a 'get' accessor. Did you mean to use it without '()'?": {
+        "category": "Message",
+        "code": 6234
+    },
 
     "Projects to reference": {
         "category": "Message",

tests/baselines/reference/accessorAccidentalCallDiagnostic.errors.txt

@@ -0,0 +1,16 @@
+tests/cases/compiler/accessorAccidentalCallDiagnostic.ts(6,14): message TS6234: This expression is not callable because it is a 'get' accessor. Did you mean to use it without '()'?
+  Type 'Number' has no call signatures.
+
+
+==== tests/cases/compiler/accessorAccidentalCallDiagnostic.ts (1 errors) ====
+    // https://github.com/microsoft/TypeScript/issues/24554
+    class Test24554 {
+        get property(): number { return 1; }
+    }
+    function test24554(x: Test24554) {
+        return x.property();
+                 ~~~~~~~~
+!!! message TS6234: This expression is not callable because it is a 'get' accessor. Did you mean to use it without '()'?
+!!! message TS6234:   Type 'Number' has no call signatures.
+    }
+

tests/baselines/reference/accessorAccidentalCallDiagnostic.js

@@ -0,0 +1,25 @@
+//// [accessorAccidentalCallDiagnostic.ts]
+// https://github.com/microsoft/TypeScript/issues/24554
+class Test24554 {
+    get property(): number { return 1; }
+}
+function test24554(x: Test24554) {
+    return x.property();
+}
+
+
+//// [accessorAccidentalCallDiagnostic.js]
+// https://github.com/microsoft/TypeScript/issues/24554
+var Test24554 = /** @class */ (function () {
+    function Test24554() {
+    }
+    Object.defineProperty(Test24554.prototype, "property", {
+        get: function () { return 1; },
+        enumerable: false,
+        configurable: true
+    });
+    return Test24554;
+}());
+function test24554(x) {
+    return x.property();
+}

tests/baselines/reference/accessorAccidentalCallDiagnostic.symbols

@@ -0,0 +1,19 @@
+=== tests/cases/compiler/accessorAccidentalCallDiagnostic.ts ===
+// https://github.com/microsoft/TypeScript/issues/24554
+class Test24554 {
+>Test24554 : Symbol(Test24554, Decl(accessorAccidentalCallDiagnostic.ts, 0, 0))
+
+    get property(): number { return 1; }
+>property : Symbol(Test24554.property, Decl(accessorAccidentalCallDiagnostic.ts, 1, 17))
+}
+function test24554(x: Test24554) {
+>test24554 : Symbol(test24554, Decl(accessorAccidentalCallDiagnostic.ts, 3, 1))
+>x : Symbol(x, Decl(accessorAccidentalCallDiagnostic.ts, 4, 19))
+>Test24554 : Symbol(Test24554, Decl(accessorAccidentalCallDiagnostic.ts, 0, 0))
+
+    return x.property();
+>x.property : Symbol(Test24554.property, Decl(accessorAccidentalCallDiagnostic.ts, 1, 17))
+>x : Symbol(x, Decl(accessorAccidentalCallDiagnostic.ts, 4, 19))
+>property : Symbol(Test24554.property, Decl(accessorAccidentalCallDiagnostic.ts, 1, 17))
+}
+

tests/baselines/reference/accessorAccidentalCallDiagnostic.types

@@ -0,0 +1,20 @@
+=== tests/cases/compiler/accessorAccidentalCallDiagnostic.ts ===
+// https://github.com/microsoft/TypeScript/issues/24554
+class Test24554 {
+>Test24554 : Test24554
+
+    get property(): number { return 1; }
+>property : number
+>1 : 1
+}
+function test24554(x: Test24554) {
+>test24554 : (x: Test24554) => any
+>x : Test24554
+
+    return x.property();
+>x.property() : any
+>x.property : number
+>x : Test24554
+>property : number
+}
+

tests/baselines/reference/instancePropertiesInheritedIntoClassType.errors.txt

@@ -1,10 +1,10 @@
 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(19,16): error TS2349: This expression is not callable.
+tests/cases/conformance/classes/members/classTypes/instancePropertiesInheritedIntoClassType.ts(19,16): message TS6234: This expression is not callable because it is a 'get' accessor. Did you mean to use it without '()'?
   Type 'Number' has no call signatures.
 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(41,16): error TS2349: This expression is not callable.
+tests/cases/conformance/classes/members/classTypes/instancePropertiesInheritedIntoClassType.ts(41,16): message TS6234: This expression is not callable because it is a 'get' accessor. Did you mean to use it without '()'?
   Type 'String' has no call signatures.
 
 
@@ -33,8 +33,8 @@ tests/cases/conformance/classes/members/classTypes/instancePropertiesInheritedIn
         r.y = 4;
         var r6 = d.y(); // error
                    ~
-!!! error TS2349: This expression is not callable.
-!!! error TS2349:   Type 'Number' has no call signatures.
+!!! message TS6234: This expression is not callable because it is a 'get' accessor. Did you mean to use it without '()'?
+!!! message TS6234:   Type 'Number' has no call signatures.
 
     }
 
@@ -62,6 +62,6 @@ tests/cases/conformance/classes/members/classTypes/instancePropertiesInheritedIn
         r.y = '';
         var r6 = d.y(); // error
                    ~
-!!! error TS2349: This expression is not callable.
-!!! error TS2349:   Type 'String' has no call signatures.
+!!! message TS6234: This expression is not callable because it is a 'get' accessor. Did you mean to use it without '()'?
+!!! message TS6234:   Type 'String' has no call signatures.
     }

tests/baselines/reference/instancePropertyInClassType.errors.txt

@@ -1,10 +1,10 @@
 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(17,16): error TS2349: This expression is not callable.
+tests/cases/conformance/classes/members/classTypes/instancePropertyInClassType.ts(17,16): message TS6234: This expression is not callable because it is a 'get' accessor. Did you mean to use it without '()'?
   Type 'Number' has no call signatures.
 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(37,16): error TS2349: This expression is not callable.
+tests/cases/conformance/classes/members/classTypes/instancePropertyInClassType.ts(37,16): message TS6234: This expression is not callable because it is a 'get' accessor. Did you mean to use it without '()'?
   Type 'String' has no call signatures.
 
 
@@ -31,8 +31,8 @@ tests/cases/conformance/classes/members/classTypes/instancePropertyInClassType.t
         r.y = 4;
         var r6 = c.y(); // error
                    ~
-!!! error TS2349: This expression is not callable.
-!!! error TS2349:   Type 'Number' has no call signatures.
+!!! message TS6234: This expression is not callable because it is a 'get' accessor. Did you mean to use it without '()'?
+!!! message TS6234:   Type 'Number' has no call signatures.
 
     }
 
@@ -58,6 +58,6 @@ tests/cases/conformance/classes/members/classTypes/instancePropertyInClassType.t
         r.y = '';
         var r6 = c.y(); // error
                    ~
-!!! error TS2349: This expression is not callable.
-!!! error TS2349:   Type 'String' has no call signatures.
+!!! message TS6234: This expression is not callable because it is a 'get' accessor. Did you mean to use it without '()'?
+!!! message TS6234:   Type 'String' has no call signatures.
     }

tests/cases/compiler/accessorAccidentalCallDiagnostic.ts

@@ -0,0 +1,9 @@
+// @target: es5
+
+// https://github.com/microsoft/TypeScript/issues/24554
+class Test24554 {
+    get property(): number { return 1; }
+}
+function test24554(x: Test24554) {
+    return x.property();
+}