improve Diagnostics for accidentally calling type-assertion expressions

src/compiler/checker.ts

@@ -19655,7 +19655,14 @@ namespace ts {
                     error(node, Diagnostics.Value_of_type_0_is_not_callable_Did_you_mean_to_include_new, typeToString(funcType));
                 }
                 else {
-                    invocationError(node, apparentType, SignatureKind.Call);
+                    let relatedInformation: DiagnosticRelatedInformation | 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);
                 }
                 return resolveErrorCall(node);
             }
@@ -19825,11 +19832,12 @@ namespace ts {
             return true;
         }
 
-        function invocationError(node: Node, apparentType: Type, kind: SignatureKind) {
-            invocationErrorRecovery(apparentType, kind, error(node, kind === SignatureKind.Call
-                ? Diagnostics.Cannot_invoke_an_expression_whose_type_lacks_a_call_signature_Type_0_has_no_compatible_call_signatures
-                : Diagnostics.Cannot_use_new_with_an_expression_whose_type_lacks_a_call_or_construct_signature
-            , typeToString(apparentType)));
+        function invocationError(node: Node, apparentType: Type, kind: SignatureKind, relatedInformation?: DiagnosticRelatedInformation) {
+            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 :
+                Diagnostics.Cannot_use_new_with_an_expression_whose_type_lacks_a_call_or_construct_signature
+            ), typeToString(apparentType));
+            invocationErrorRecovery(apparentType, kind, relatedInformation ? addRelatedInfo(diagnostic, relatedInformation) : diagnostic);
         }
 
         function invocationErrorRecovery(apparentType: Type, kind: SignatureKind, diagnostic: Diagnostic) {

src/compiler/diagnosticMessages.json

@@ -2457,6 +2457,10 @@
         "category": "Error",
         "code": 2733
     },
+    "It is highly likely that you are missing a semicolon.": {
+        "category": "Error",
+        "code": 2734
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",

tests/baselines/reference/betterErrorForAccidentallyCallingTypeAssertionExpressions.errors.txt

@@ -0,0 +1,39 @@
+tests/cases/compiler/betterErrorForAccidentallyCallingTypeAssertionExpressions.ts(3,1): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+tests/cases/compiler/betterErrorForAccidentallyCallingTypeAssertionExpressions.ts(5,1): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+tests/cases/compiler/betterErrorForAccidentallyCallingTypeAssertionExpressions.ts(7,1): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+tests/cases/compiler/betterErrorForAccidentallyCallingTypeAssertionExpressions.ts(10,1): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+tests/cases/compiler/betterErrorForAccidentallyCallingTypeAssertionExpressions.ts(13,1): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+
+
+==== tests/cases/compiler/betterErrorForAccidentallyCallingTypeAssertionExpressions.ts (5 errors) ====
+    declare function foo(): string;
+
+    foo()(1 as number).toString();
+    ~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+
+    foo()   (1 as number).toString();
+    ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+
+    foo()
+    ~~~~~
+    (1 as number).toString();
+    ~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+!!! related TS2734 tests/cases/compiler/betterErrorForAccidentallyCallingTypeAssertionExpressions.ts:7:1: It is highly likely that you are missing a semicolon.
+
+    foo()   
+    ~~~~~~~~
+        (1 as number).toString();
+    ~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+!!! related TS2734 tests/cases/compiler/betterErrorForAccidentallyCallingTypeAssertionExpressions.ts:10:1: It is highly likely that you are missing a semicolon.
+
+    foo()   
+    ~~~~~~~~
+        (<number>1).toString();
+    ~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+!!! related TS2734 tests/cases/compiler/betterErrorForAccidentallyCallingTypeAssertionExpressions.ts:13:1: It is highly likely that you are missing a semicolon.
+

tests/baselines/reference/betterErrorForAccidentallyCallingTypeAssertionExpressions.js

@@ -0,0 +1,23 @@
+//// [betterErrorForAccidentallyCallingTypeAssertionExpressions.ts]
+declare function foo(): string;
+
+foo()(1 as number).toString();
+
+foo()   (1 as number).toString();
+
+foo()
+(1 as number).toString();
+
+foo()   
+    (1 as number).toString();
+
+foo()   
+    (<number>1).toString();
+
+
+//// [betterErrorForAccidentallyCallingTypeAssertionExpressions.js]
+foo()(1).toString();
+foo()(1).toString();
+foo()(1).toString();
+foo()(1).toString();
+foo()(1).toString();

tests/baselines/reference/betterErrorForAccidentallyCallingTypeAssertionExpressions.symbols

@@ -0,0 +1,25 @@
+=== tests/cases/compiler/betterErrorForAccidentallyCallingTypeAssertionExpressions.ts ===
+declare function foo(): string;
+>foo : Symbol(foo, Decl(betterErrorForAccidentallyCallingTypeAssertionExpressions.ts, 0, 0))
+
+foo()(1 as number).toString();
+>foo : Symbol(foo, Decl(betterErrorForAccidentallyCallingTypeAssertionExpressions.ts, 0, 0))
+
+foo()   (1 as number).toString();
+>foo : Symbol(foo, Decl(betterErrorForAccidentallyCallingTypeAssertionExpressions.ts, 0, 0))
+
+foo()
+>foo : Symbol(foo, Decl(betterErrorForAccidentallyCallingTypeAssertionExpressions.ts, 0, 0))
+
+(1 as number).toString();
+
+foo()   
+>foo : Symbol(foo, Decl(betterErrorForAccidentallyCallingTypeAssertionExpressions.ts, 0, 0))
+
+    (1 as number).toString();
+
+foo()   
+>foo : Symbol(foo, Decl(betterErrorForAccidentallyCallingTypeAssertionExpressions.ts, 0, 0))
+
+    (<number>1).toString();
+

tests/baselines/reference/betterErrorForAccidentallyCallingTypeAssertionExpressions.types

@@ -0,0 +1,60 @@
+=== tests/cases/compiler/betterErrorForAccidentallyCallingTypeAssertionExpressions.ts ===
+declare function foo(): string;
+>foo : () => string
+
+foo()(1 as number).toString();
+>foo()(1 as number).toString() : any
+>foo()(1 as number).toString : any
+>foo()(1 as number) : any
+>foo() : string
+>foo : () => string
+>1 as number : number
+>1 : 1
+>toString : any
+
+foo()   (1 as number).toString();
+>foo()   (1 as number).toString() : any
+>foo()   (1 as number).toString : any
+>foo()   (1 as number) : any
+>foo() : string
+>foo : () => string
+>1 as number : number
+>1 : 1
+>toString : any
+
+foo()
+>foo()(1 as number).toString() : any
+>foo()(1 as number).toString : any
+>foo()(1 as number) : any
+>foo() : string
+>foo : () => string
+
+(1 as number).toString();
+>1 as number : number
+>1 : 1
+>toString : any
+
+foo()   
+>foo()       (1 as number).toString() : any
+>foo()       (1 as number).toString : any
+>foo()       (1 as number) : any
+>foo() : string
+>foo : () => string
+
+    (1 as number).toString();
+>1 as number : number
+>1 : 1
+>toString : any
+
+foo()   
+>foo()       (<number>1).toString() : any
+>foo()       (<number>1).toString : any
+>foo()       (<number>1) : any
+>foo() : string
+>foo : () => string
+
+    (<number>1).toString();
+><number>1 : number
+>1 : 1
+>toString : any
+

tests/cases/compiler/betterErrorForAccidentallyCallingTypeAssertionExpressions.ts

@@ -0,0 +1,14 @@
+declare function foo(): string;
+
+foo()(1 as number).toString();
+
+foo()   (1 as number).toString();
+
+foo()
+(1 as number).toString();
+
+foo()   
+    (1 as number).toString();
+
+foo()   
+    (<number>1).toString();