fix #1560: bug with "!" after "new" in TypeScript

CHANGELOG.md

@@ -1,5 +1,24 @@
 # Changelog
 
+## Unreleased
+
+* Fix a TypeScript parsing edge case with the postfix `!` operator ([#1560](https://github.com/evanw/esbuild/issues/1560))
+
+    This release fixes a bug with esbuild's TypeScript parser where the postfix `!` operator incorrectly terminated a member expression after the `new` operator:
+
+    ```js
+    // Original input
+    new Foo!.Bar();
+
+    // Old output
+    new Foo().Bar();
+
+    // New output
+    new Foo.Bar();
+    ```
+
+    The problem was that `!` was considered a postfix operator instead of part of a member expression. It is now considered to be part of a member expression instead, which fixes this edge case.
+
 ## 0.12.24
 
 * Fix an edge case with direct `eval` and variable renaming

internal/js_parser/js_parser.go

@@ -3109,18 +3109,6 @@ func (p *parser) parsePrefix(level js_ast.L, errors *deferredErrors, flags exprF
 		target := p.parseExprWithFlags(js_ast.LMember, flags)
 		args := []js_ast.Expr{}
 
-		if p.options.ts.Parse {
-			// Skip over TypeScript non-null assertions
-			if p.lexer.Token == js_lexer.TExclamation && !p.lexer.HasNewlineBefore {
-				p.lexer.Next()
-			}
-
-			// Skip over TypeScript type arguments here if there are any
-			if p.lexer.Token == js_lexer.TLessThan {
-				p.trySkipTypeScriptTypeArgumentsWithBacktracking()
-			}
-		}
-
 		if p.lexer.Token == js_lexer.TOpenParen {
 			args = p.parseCallArgs()
 		}
@@ -3779,9 +3767,6 @@ func (p *parser) parseSuffix(left js_ast.Expr, level js_ast.L, errors *deferredE
 			if !p.options.ts.Parse {
 				p.lexer.Unexpected()
 			}
-			if level >= js_ast.LPostfix {
-				return left
-			}
 			p.lexer.Next()
 			optionalChain = oldOptionalChain
 

internal/js_parser/ts_parser_test.go

@@ -1354,9 +1354,13 @@ func TestTSNew(t *testing.T) {
 
 	expectPrintedTS(t, "new Foo!()", "new Foo();\n")
 	expectPrintedTS(t, "new Foo!<number>()", "new Foo();\n")
+	expectPrintedTS(t, "new Foo!.Bar()", "new Foo.Bar();\n")
+	expectPrintedTS(t, "new Foo!.Bar<number>()", "new Foo.Bar();\n")
+	expectPrintedTS(t, "new Foo!['Bar']()", "new Foo[\"Bar\"]();\n")
 	expectPrintedTS(t, "new Foo\n!(x)", "new Foo();\n!x;\n")
 	expectPrintedTS(t, "new Foo<number>!(x)", "new Foo() < number > !x;\n")
 	expectParseErrorTS(t, "new Foo<number>!()", "<stdin>: error: Unexpected \")\"\n")
+	expectParseErrorTS(t, "new Foo\n!.Bar()", "<stdin>: error: Unexpected \".\"\n")
 	expectParseError(t, "new Foo!()", "<stdin>: error: Unexpected \"!\"\n")
 }