allow in and out with class expression params

CHANGELOG.md

@@ -1,5 +1,17 @@
 # Changelog
 
+## Unreleased
+
+* Allow the `in` and `out` type parameter modifiers on class expressions
+
+    TypeScript 4.7 added the `in` and `out` modifiers on the type parameters of classes, interfaces, and type aliases. However, while TypeScript supported them on both class expressions and class statements, previously esbuild only supported them on class statements due to an oversight. This release now allows these modifiers on class expressions too:
+
+    ```ts
+    declare let Foo: any;
+    Foo = class <in T> { };
+    Foo = class <out T> { };
+    ```
+
 ## 0.17.4
 
 * Implement HTTP `HEAD` requests in serve mode ([#2851](https://github.com/evanw/esbuild/issues/2851))

internal/js_parser/js_parser.go

@@ -3428,7 +3428,7 @@ func (p *parser) parsePrefix(level js_ast.L, errors *deferredErrors, flags exprF
 
 		// Even anonymous classes can have TypeScript type parameters
 		if p.options.ts.Parse {
-			p.skipTypeScriptTypeParameters(typeParametersNormal)
+			p.skipTypeScriptTypeParameters(typeParametersWithInOutVarianceAnnotations)
 		}
 
 		class := p.parseClass(classKeyword, name, parseClassOpts{})

internal/js_parser/ts_parser_test.go

@@ -338,8 +338,10 @@ func TestTSTypes(t *testing.T) {
 	expectParseErrorTS(t, "declare function foo<out T>()", "<stdin>: ERROR: The modifier \"out\" is not valid here:\n")
 	expectParseErrorTS(t, "declare let foo: Foo<in T>", "<stdin>: ERROR: Unexpected \"in\"\n")
 	expectParseErrorTS(t, "declare let foo: Foo<out T>", "<stdin>: ERROR: Expected \">\" but found \"T\"\n")
-	expectParseErrorTS(t, "Foo = class <in T> {}", "<stdin>: ERROR: The modifier \"in\" is not valid here:\n")
-	expectParseErrorTS(t, "Foo = class <out T> {}", "<stdin>: ERROR: The modifier \"out\" is not valid here:\n")
+	expectPrintedTS(t, "Foo = class <in T> {}", "Foo = class {\n};\n")
+	expectPrintedTS(t, "Foo = class <out T> {}", "Foo = class {\n};\n")
+	expectPrintedTS(t, "Foo = class Bar<in T> {}", "Foo = class Bar {\n};\n")
+	expectPrintedTS(t, "Foo = class Bar<out T> {}", "Foo = class Bar {\n};\n")
 	expectParseErrorTS(t, "foo = function <in T>() {}", "<stdin>: ERROR: The modifier \"in\" is not valid here:\n")
 	expectParseErrorTS(t, "foo = function <out T>() {}", "<stdin>: ERROR: The modifier \"out\" is not valid here:\n")
 	expectParseErrorTS(t, "class Foo { foo<in T>(): T {} }", "<stdin>: ERROR: The modifier \"in\" is not valid here:\n")