improve Diagnostics for accidentally calling type-assertion expressions

src/compiler/checker.ts

@@ -19655,6 +19655,13 @@ namespace ts {
                     error(node, Diagnostics.Value_of_type_0_is_not_callable_Did_you_mean_to_include_new, typeToString(funcType));
                 }
                 else {
+                    if (node.arguments.length === 1 && isTypeAssertion(first(node.arguments))) {
+                        const text = getSourceFileOfNode(node).text;
+                        const pos = skipTrivia(text, node.expression.end, /* stepAfterLineBreak */ true) - 1;
+                        if (isLineBreak(text.charCodeAt(pos))) {
+                            error(node.expression, Diagnostics.It_is_highly_likely_that_you_are_missing_a_semicolon);
+                        }
+                    }
                     invocationError(node, apparentType, SignatureKind.Call);
                 }
                 return resolveErrorCall(node);

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 +1,35 @@
+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 TS2734: It is highly likely that you are missing a semicolon.
+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 TS2734: It is highly likely that you are missing a semicolon.
+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 (6 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()
+    ~~~~~
+!!! error TS2734: It is highly likely that you are missing a semicolon.
+    ~~~~~
+    (1 as number).toString();
+    ~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+    
+    foo()   
+    ~~~~~
+!!! error TS2734: It is highly likely that you are missing a semicolon.
+    ~~~~~~~~
+        (1 as number).toString();
+    ~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'String' has no compatible call signatures.
+    

tests/baselines/reference/betterErrorForAccidentallyCallingTypeAssertionExpressions.js

@@ -0,0 +1,19 @@
+//// [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();
+
+
+//// [betterErrorForAccidentallyCallingTypeAssertionExpressions.js]
+foo()(1).toString();
+foo()(1).toString();
+foo()(1).toString();
+foo()(1).toString();

tests/baselines/reference/betterErrorForAccidentallyCallingTypeAssertionExpressions.symbols

@@ -0,0 +1,20 @@
+=== 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();
+

tests/baselines/reference/betterErrorForAccidentallyCallingTypeAssertionExpressions.types

@@ -0,0 +1,48 @@
+=== 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
+

tests/cases/compiler/betterErrorForAccidentallyCallingTypeAssertionExpressions.ts

@@ -0,0 +1,11 @@
+declare function foo(): string;
+
+foo()(1 as number).toString();
+
+foo()   (1 as number).toString();
+
+foo()
+(1 as number).toString();
+
+foo()   
+    (1 as number).toString();