fix #2991: crash with inline typescript decorator

CHANGELOG.md

@@ -1,5 +1,21 @@
 # Changelog
 
+## Unreleased
+
+* Fix a crash when parsing inline TypeScript decorators ([#2991](https://github.com/evanw/esbuild/issues/2991))
+
+    Previously esbuild's TypeScript parser crashed when parsing TypeScript decorators if the definition of the decorator was inlined into the decorator itself:
+
+    ```ts
+    @(function sealed(constructor: Function) {
+      Object.seal(constructor);
+      Object.seal(constructor.prototype);
+    })
+    class Foo {}
+    ```
+
+    This crash was not noticed earlier because this edge case did not have test coverage. The crash is fixed in this release.
+
 ## 0.17.11
 
 * Fix the `alias` feature to always prefer the longest match ([#2963](https://github.com/evanw/esbuild/issues/2963))

internal/js_parser/ts_parser.go

@@ -1245,7 +1245,6 @@ func (p *parser) parseTypeScriptDecorators(tsDecoratorScope *js_ast.Scope) []js_
 		p.currentScope = tsDecoratorScope
 
 		for p.lexer.Token == js_lexer.TAt {
-			loc := p.lexer.Loc()
 			p.lexer.Next()
 
 			// Parse a new/call expression with "exprFlagTSDecorator" so we ignore
@@ -1257,7 +1256,6 @@ func (p *parser) parseTypeScriptDecorators(tsDecoratorScope *js_ast.Scope) []js_
 			//
 			// This matches the behavior of the TypeScript compiler.
 			value := p.parseExprWithFlags(js_ast.LNew, exprFlagTSDecorator)
-			value.Loc = loc
 			tsDecorators = append(tsDecorators, value)
 		}
 

internal/js_parser/ts_parser_test.go

@@ -1773,6 +1773,12 @@ func TestTSDecorator(t *testing.T) {
 		"<stdin>: ERROR: Cannot use \"yield\" outside a generator function\n")
 	expectParseErrorTS(t, "function foo() { @dec(yield x) class Foo {} }", "<stdin>: ERROR: Cannot use \"yield\" outside a generator function\n")
 	expectParseErrorTS(t, "function foo() { class Foo { @dec(yield x) foo() {} } }", "<stdin>: ERROR: Cannot use \"yield\" outside a generator function\n")
+
+	// Check inline function expressions
+	expectPrintedTS(t, "@((x, y) => x + y) class Foo {}", "let Foo = class {\n};\nFoo = __decorateClass([\n  (x, y) => x + y\n], Foo);\n")
+	expectPrintedTS(t, "@((x, y) => x + y) export class Foo {}", "export let Foo = class {\n};\nFoo = __decorateClass([\n  (x, y) => x + y\n], Foo);\n")
+	expectPrintedTS(t, "@(function(x, y) { return x + y }) class Foo {}", "let Foo = class {\n};\nFoo = __decorateClass([\n  function(x, y) {\n    return x + y;\n  }\n], Foo);\n")
+	expectPrintedTS(t, "@(function(x, y) { return x + y }) export class Foo {}", "export let Foo = class {\n};\nFoo = __decorateClass([\n  function(x, y) {\n    return x + y;\n  }\n], Foo);\n")
 }
 
 func TestTSTry(t *testing.T) {