Ensure we treat "type assertions" as JSX within a unary expression (#52667)

Author: jakebailey

src/compiler/parser.ts

@@ -5648,6 +5648,11 @@ namespace Parser {
             case SyntaxKind.VoidKeyword:
                 return parseVoidExpression();
             case SyntaxKind.LessThanToken:
+                // Just like in parseUpdateExpression, we need to avoid parsing type assertions when
+                // in JSX and we see an expression like "+ <foo> bar".
+                if (languageVariant === LanguageVariant.JSX) {
+                    return parseJsxElementOrSelfClosingElementOrFragment(/*inExpressionContext*/ true);
+                }
                 // This is modified UnaryExpression grammar in TypeScript
                 //  UnaryExpression (modified):
                 //      < type > UnaryExpression
@@ -6163,6 +6168,7 @@ namespace Parser {
     }
 
     function parseTypeAssertion(): TypeAssertion {
+        Debug.assert(scriptKind === ScriptKind.TS, "Type assertions should never be parsed outside of TS; they should either be comparisons or JSX.");
         const pos = getNodePos();
         parseExpected(SyntaxKind.LessThanToken);
         const type = parseType();

tests/baselines/reference/parseUnaryExpressionNoTypeAssertionInJsx1.errors.txt

@@ -0,0 +1,15 @@
+tests/cases/compiler/index.js(2,13): error TS17004: Cannot use JSX unless the '--jsx' flag is provided.
+tests/cases/compiler/index.js(2,14): error TS17008: JSX element 'number' has no corresponding closing tag.
+tests/cases/compiler/index.js(3,1): error TS1005: '</' expected.
+
+
+==== tests/cases/compiler/index.js (3 errors) ====
+    const x = "oops";
+    const y = + <number> x;
+                ~~~~~~~~
+!!! error TS17004: Cannot use JSX unless the '--jsx' flag is provided.
+                 ~~~~~~
+!!! error TS17008: JSX element 'number' has no corresponding closing tag.
+    
+    
+!!! error TS1005: '</' expected.

tests/baselines/reference/parseUnaryExpressionNoTypeAssertionInJsx1.symbols

@@ -0,0 +1,7 @@
+=== tests/cases/compiler/index.js ===
+const x = "oops";
+>x : Symbol(x, Decl(index.js, 0, 5))
+
+const y = + <number> x;
+>y : Symbol(y, Decl(index.js, 1, 5))
+

tests/baselines/reference/parseUnaryExpressionNoTypeAssertionInJsx1.types

@@ -0,0 +1,13 @@
+=== tests/cases/compiler/index.js ===
+const x = "oops";
+>x : "oops"
+>"oops" : "oops"
+
+const y = + <number> x;
+>y : number
+>+ <number> x; : number
+><number> x; : any
+>number : any
+
+> : any
+

tests/baselines/reference/parseUnaryExpressionNoTypeAssertionInJsx2.errors.txt

@@ -0,0 +1,15 @@
+tests/cases/compiler/index.js(2,12): error TS17014: JSX fragment has no corresponding closing tag.
+tests/cases/compiler/index.js(2,13): error TS17004: Cannot use JSX unless the '--jsx' flag is provided.
+tests/cases/compiler/index.js(3,1): error TS1005: '</' expected.
+
+
+==== tests/cases/compiler/index.js (3 errors) ====
+    const x = "oops";
+    const y = + <> x;
+               ~~~
+!!! error TS17014: JSX fragment has no corresponding closing tag.
+                ~~
+!!! error TS17004: Cannot use JSX unless the '--jsx' flag is provided.
+    
+    
+!!! error TS1005: '</' expected.

tests/baselines/reference/parseUnaryExpressionNoTypeAssertionInJsx2.symbols

@@ -0,0 +1,7 @@
+=== tests/cases/compiler/index.js ===
+const x = "oops";
+>x : Symbol(x, Decl(index.js, 0, 5))
+
+const y = + <> x;
+>y : Symbol(y, Decl(index.js, 1, 5))
+

tests/baselines/reference/parseUnaryExpressionNoTypeAssertionInJsx2.types

@@ -0,0 +1,10 @@
+=== tests/cases/compiler/index.js ===
+const x = "oops";
+>x : "oops"
+>"oops" : "oops"
+
+const y = + <> x;
+>y : number
+>+ <> x; : number
+><> x; : any
+

tests/baselines/reference/parseUnaryExpressionNoTypeAssertionInJsx3.errors.txt

@@ -0,0 +1,15 @@
+tests/cases/compiler/index.js(2,13): error TS17004: Cannot use JSX unless the '--jsx' flag is provided.
+tests/cases/compiler/index.js(2,14): error TS1003: Identifier expected.
+tests/cases/compiler/index.js(2,14): error TS2365: Operator '>' cannot be applied to types 'number' and 'string'.
+
+
+==== tests/cases/compiler/index.js (3 errors) ====
+    const x = "oops";
+    const y = + <1234> x;
+                ~
+!!! error TS17004: Cannot use JSX unless the '--jsx' flag is provided.
+                 ~~~~
+!!! error TS1003: Identifier expected.
+                 ~~~~~~~
+!!! error TS2365: Operator '>' cannot be applied to types 'number' and 'string'.
+    

tests/baselines/reference/parseUnaryExpressionNoTypeAssertionInJsx3.symbols

@@ -0,0 +1,8 @@
+=== tests/cases/compiler/index.js ===
+const x = "oops";
+>x : Symbol(x, Decl(index.js, 0, 5))
+
+const y = + <1234> x;
+>y : Symbol(y, Decl(index.js, 1, 5))
+>x : Symbol(x, Decl(index.js, 0, 5))
+

tests/baselines/reference/parseUnaryExpressionNoTypeAssertionInJsx3.types

@@ -0,0 +1,14 @@
+=== tests/cases/compiler/index.js ===
+const x = "oops";
+>x : "oops"
+>"oops" : "oops"
+
+const y = + <1234> x;
+>y : number
+>+ < : number
+>< : any
+> : any
+>1234> x : boolean
+>1234 : 1234
+>x : "oops"
+

tests/baselines/reference/parseUnaryExpressionNoTypeAssertionInJsx4.errors.txt

@@ -0,0 +1,24 @@
+tests/cases/compiler/index.tsx(3,14): error TS17008: JSX element 'number' has no corresponding closing tag.
+tests/cases/compiler/index.tsx(4,13): error TS17014: JSX fragment has no corresponding closing tag.
+tests/cases/compiler/index.tsx(5,14): error TS1003: Identifier expected.
+tests/cases/compiler/index.tsx(5,18): error TS1382: Unexpected token. Did you mean `{'>'}` or `>`?
+tests/cases/compiler/index.tsx(6,1): error TS1005: '</' expected.
+
+
+==== tests/cases/compiler/index.tsx (5 errors) ====
+    const x = "oops";
+    
+    const a = + <number> x;
+                 ~~~~~~
+!!! error TS17008: JSX element 'number' has no corresponding closing tag.
+    const b = + <> x;
+                ~~
+!!! error TS17014: JSX fragment has no corresponding closing tag.
+    const c = + <1234> x;
+                 ~~~~
+!!! error TS1003: Identifier expected.
+                     ~
+!!! error TS1382: Unexpected token. Did you mean `{'>'}` or `&gt;`?
+    
+    
+!!! error TS1005: '</' expected.

tests/baselines/reference/parseUnaryExpressionNoTypeAssertionInJsx4.js

@@ -0,0 +1,14 @@
+//// [index.tsx]
+const x = "oops";
+
+const a = + <number> x;
+const b = + <> x;
+const c = + <1234> x;
+
+
+//// [index.jsx]
+var x = "oops";
+var a = +<number> x;
+const b = + <> x;
+const c = + < />1234> x;
+</></>;

tests/baselines/reference/parseUnaryExpressionNoTypeAssertionInJsx4.symbols

@@ -0,0 +1,10 @@
+=== tests/cases/compiler/index.tsx ===
+const x = "oops";
+>x : Symbol(x, Decl(index.tsx, 0, 5))
+
+const a = + <number> x;
+>a : Symbol(a, Decl(index.tsx, 2, 5))
+
+const b = + <> x;
+const c = + <1234> x;
+

tests/baselines/reference/parseUnaryExpressionNoTypeAssertionInJsx4.types

@@ -0,0 +1,20 @@
+=== tests/cases/compiler/index.tsx ===
+const x = "oops";
+>x : "oops"
+>"oops" : "oops"
+
+const a = + <number> x;
+>a : number
+>+ <number> x;const b = + <> x;const c = + <1234> x; : number
+><number> x;const b = + <> x;const c = + <1234> x; : any
+>number : any
+
+const b = + <> x;
+><> x;const c = + <1234> x; : any
+
+const c = + <1234> x;
+>< : any
+> : any
+
+> : any
+

tests/cases/compiler/parseUnaryExpressionNoTypeAssertionInJsx1.ts

@@ -0,0 +1,7 @@
+// @allowJs: true
+// @noEmit: true
+// @checkJs: true
+// @filename: index.js
+
+const x = "oops";
+const y = + <number> x;

tests/cases/compiler/parseUnaryExpressionNoTypeAssertionInJsx2.ts

@@ -0,0 +1,7 @@
+// @allowJs: true
+// @noEmit: true
+// @checkJs: true
+// @filename: index.js
+
+const x = "oops";
+const y = + <> x;

tests/cases/compiler/parseUnaryExpressionNoTypeAssertionInJsx3.ts

@@ -0,0 +1,7 @@
+// @allowJs: true
+// @noEmit: true
+// @checkJs: true
+// @filename: index.js
+
+const x = "oops";
+const y = + <1234> x;

tests/cases/compiler/parseUnaryExpressionNoTypeAssertionInJsx4.ts

@@ -0,0 +1,8 @@
+// @filename: index.tsx
+// @jsx: preserve
+
+const x = "oops";
+
+const a = + <number> x;
+const b = + <> x;
+const c = + <1234> x;