fix(parser): span ambient generator diagnostics (#24711)

## Summary

Make TS1221 underline the generator declaration consistently from the `*` token.

## Why

The previous diagnostic used the generic function span, but that span has different start points depending on how the function is parsed:

- A class method enters function parsing after its name, so `declare class C { *generator(): any; }` highlighted only `(): any;` (starting at column 15), omitting both the generator marker and its name.
- A function declaration starts its span at the `function` keyword, so `declare namespace M { function *generator(): any; }` highlighted the whole declaration (starting at column 5), including text that is not the invalid generator construct.

For example, the prior output treated these equivalent generator markers differently:

```ts
declare class C {
    *generator(): any;
//            ^^^^^^^^
}

declare namespace M {
    function *generator(): any;
//  ^^^^^^^^^^^^^^^^^^^^^^^^^^^
}
```

The parser now carries the `*` token location as `Option<u32>` while parsing a function. TS1221 uses that location through the declaration end, so both cases consistently highlight the relevant generator declaration:

```ts
*generator(): any;
^^^^^^^^^^^^^^^^^^
```

The AST continues to store `generator` as a boolean; the location exists only while parsing diagnostics.

crates/oxc_parser/src/js/class.rs

@@ -471,7 +471,7 @@ impl<'a, C: Config> ParserImpl<'a, C> {
         let (name, computed) = self.parse_class_element_name(modifiers);
         let value = self.parse_method(
             modifiers.contains(ModifierKind::Async),
-            false,
+            None,
             FunctionKind::ClassMethod,
         );
         let method_definition = MethodDefinition::boxed(
@@ -512,7 +512,7 @@ impl<'a, C: Config> ParserImpl<'a, C> {
 
         let value = self.parse_method(
             modifiers.contains(ModifierKind::Async),
-            false,
+            None,
             FunctionKind::Constructor,
         );
         let method_definition = MethodDefinition::boxed(
@@ -555,7 +555,7 @@ impl<'a, C: Config> ParserImpl<'a, C> {
         modifiers: &Modifiers,
         decorators: ArenaVec<'a, Decorator<'a>>,
     ) -> ClassElement<'a> {
-        let generator = self.eat(Kind::Star);
+        let generator = self.eat(Kind::Star).then_some(self.prev_token_end - 1);
         let (name, computed) = self.parse_class_element_name(modifiers);
 
         let cur_token = self.cur_token();
@@ -567,7 +567,7 @@ impl<'a, C: Config> ParserImpl<'a, C> {
 
         let optional = optional_span.is_some();
 
-        if generator || matches!(self.cur_kind(), Kind::LParen | Kind::LAngle) {
+        if generator.is_some() || matches!(self.cur_kind(), Kind::LParen | Kind::LAngle) {
             self.verify_modifiers(
                 modifiers,
                 ModifierKinds::all_except([ModifierKind::Declare, ModifierKind::Readonly]),
@@ -636,7 +636,7 @@ impl<'a, C: Config> ParserImpl<'a, C> {
         &mut self,
         span: u32,
         r#type: MethodDefinitionType,
-        generator: bool,
+        generator: Option<u32>,
         name: PropertyKey<'a>,
         computed: bool,
         optional: bool,

crates/oxc_parser/src/js/function.rs

@@ -257,7 +257,7 @@ impl<'a, C: Config> ParserImpl<'a, C> {
         span: u32,
         id: Option<BindingIdentifier<'a>>,
         r#async: bool,
-        generator: bool,
+        generator: Option<u32>,
         func_kind: FunctionKind,
         param_kind: FormalParameterKind,
         modifiers: &Modifiers,
@@ -265,8 +265,12 @@ impl<'a, C: Config> ParserImpl<'a, C> {
         let ctx = self.ctx;
         // `new.target` is allowed in a function's parameters and body (but not arrow
         // functions, which are parsed via `parse_function_body` directly).
-        self.ctx =
-            self.ctx.and_in(true).and_await(r#async).and_yield(generator).and_new_target(true);
+        self.ctx = self
+            .ctx
+            .and_in(true)
+            .and_await(r#async)
+            .and_yield(generator.is_some())
+            .and_new_target(true);
         let type_parameters = self.parse_ts_type_parameters();
         let (this_param, params) = self.parse_formal_parameters(func_kind, param_kind);
         let return_type = if self.is_ts { self.parse_ts_return_type_annotation() } else { None };
@@ -328,9 +332,9 @@ impl<'a, C: Config> ParserImpl<'a, C> {
             self.error(diagnostics::implementation_in_ambient(Span::empty(body.span.start)));
         }
 
-        if generator {
+        if let Some(generator) = generator {
             if ctx.has_ambient() {
-                self.error(diagnostics::generator_in_ambient_context(self.end_span(span)));
+                self.error(diagnostics::generator_in_ambient_context(self.end_span(generator)));
             } else if body.is_none() {
                 self.error(diagnostics::overload_signature_generator(self.end_span(span)));
             }
@@ -346,7 +350,7 @@ impl<'a, C: Config> ParserImpl<'a, C> {
             self.end_span(span),
             function_type,
             id,
-            generator,
+            generator.is_some(),
             r#async,
             modifiers.contains_declare(),
             type_parameters,
@@ -392,8 +396,8 @@ impl<'a, C: Config> ParserImpl<'a, C> {
         func_kind: FunctionKind,
     ) -> ArenaBox<'a, Function<'a>> {
         self.expect(Kind::Function);
-        let generator = self.eat(Kind::Star);
-        let id = self.parse_function_id(func_kind, r#async, generator);
+        let generator = self.eat(Kind::Star).then_some(self.prev_token_end - 1);
+        let id = self.parse_function_id(func_kind, r#async, generator.is_some());
         self.parse_function(
             span,
             id,
@@ -415,8 +419,8 @@ impl<'a, C: Config> ParserImpl<'a, C> {
     ) -> ArenaBox<'a, Function<'a>> {
         let r#async = modifiers.contains(ModifierKind::Async);
         self.expect(Kind::Function);
-        let generator = self.eat(Kind::Star);
-        let id = self.parse_function_id(func_kind, r#async, generator);
+        let generator = self.eat(Kind::Star).then_some(self.prev_token_end - 1);
+        let id = self.parse_function_id(func_kind, r#async, generator.is_some());
         self.parse_function(
             start_span,
             id,
@@ -433,8 +437,8 @@ impl<'a, C: Config> ParserImpl<'a, C> {
         let func_kind = FunctionKind::Expression;
         self.expect(Kind::Function);
 
-        let generator = self.eat(Kind::Star);
-        let id = self.parse_function_id(func_kind, r#async, generator);
+        let generator = self.eat(Kind::Star).then_some(self.prev_token_end - 1);
+        let id = self.parse_function_id(func_kind, r#async, generator.is_some());
         let function = self.parse_function(
             span,
             id,
@@ -458,7 +462,7 @@ impl<'a, C: Config> ParserImpl<'a, C> {
     pub(crate) fn parse_method(
         &mut self,
         r#async: bool,
-        generator: bool,
+        generator: Option<u32>,
         func_kind: FunctionKind,
     ) -> ArenaBox<'a, Function<'a>> {
         let span = self.start_span();

crates/oxc_parser/src/js/object.rs

@@ -59,12 +59,12 @@ impl<'a, C: Config> ParserImpl<'a, C> {
             return self.parse_method_getter_setter(span, PropertyKind::Set, &modifiers);
         }
 
-        let asterisk_token = self.eat(Kind::Star);
+        let asterisk_token = self.eat(Kind::Star).then_some(self.prev_token_end - 1);
         let token_is_identifier =
             self.cur_kind().is_identifier_reference(self.ctx.has_yield(), self.ctx.has_await());
         let (key, computed) = self.parse_property_name();
 
-        if asterisk_token || matches!(self.cur_kind(), Kind::LParen | Kind::LAngle) {
+        if asterisk_token.is_some() || matches!(self.cur_kind(), Kind::LParen | Kind::LAngle) {
             self.verify_modifiers(
                 &modifiers,
                 ModifierKinds::new([ModifierKind::Async]),
@@ -216,7 +216,7 @@ impl<'a, C: Config> ParserImpl<'a, C> {
         modifiers: &Modifiers,
     ) -> ArenaBox<'a, ObjectProperty<'a>> {
         let (key, computed) = self.parse_property_name();
-        let function = self.parse_method(false, false, FunctionKind::ObjectMethod);
+        let function = self.parse_method(false, None, FunctionKind::ObjectMethod);
         match kind {
             PropertyKind::Get => self.check_getter(&function),
             PropertyKind::Set => self.check_setter(&function),

crates/oxc_parser/src/ts/statement.rs

@@ -691,9 +691,9 @@ impl<'a, C: Config> ParserImpl<'a, C> {
     ) -> ArenaBox<'a, Function<'a>> {
         let r#async = modifiers.contains(ModifierKind::Async);
         self.expect(Kind::Function);
-        let generator = self.eat(Kind::Star);
+        let generator = self.eat(Kind::Star).then_some(self.prev_token_end - 1);
         let func_kind = FunctionKind::TSDeclaration;
-        let id = self.parse_function_id(func_kind, r#async, generator);
+        let id = self.parse_function_id(func_kind, r#async, generator.is_some());
         self.parse_function(
             start_span,
             id,

tasks/coverage/snapshots/parser_babel.snap

@@ -12820,10 +12820,10 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
   help: Allowed modifiers are: private, protected, public, static, abstract, override, async
 
   × TS(1221): Generators are not allowed in an ambient context.
-   ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/generator-method-with-modifiers/input.ts:7:13]
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/generator-method-with-modifiers/input.ts:7:11]
  6 │   readonly *e() {}
  7 │   declare *f() {}
-   ·             ─────
+   ·           ───────
  8 │   protected *g() {}
    ╰────
 
@@ -13189,10 +13189,10 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
   help: Allowed modifiers are: private, protected, public, static, abstract, override, async
 
   × TS(1221): Generators are not allowed in an ambient context.
-   ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/optional-generator-method-with-invalid-modifiers/input.ts:4:14]
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/optional-generator-method-with-invalid-modifiers/input.ts:4:11]
  3 │   readonly *e?() { }
  4 │   declare *f?() { }
-   ·              ──────
+   ·           ─────────
  5 │ }
    ╰────
 
@@ -13231,10 +13231,10 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
   help: Allowed modifiers are: private, protected, public, static, abstract, override, async
 
   × TS(1221): Generators are not allowed in an ambient context.
-    ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/optional-generator-method-with-invalid-modifiers/input.ts:10:19]
+    ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/optional-generator-method-with-invalid-modifiers/input.ts:10:11]
   9 │   readonly *[e?.e]?() { }
  10 │   declare *[f?.f]?() { }
-    ·                   ──────
+    ·           ──────────────
  11 │ }
     ╰────
 

tasks/coverage/snapshots/parser_typescript.snap

@@ -20225,34 +20225,34 @@ Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/types/wit
    ╰────
 
   × TS(1221): Generators are not allowed in an ambient context.
-   ╭─[typescript/tests/cases/conformance/es6/yieldExpressions/generatorInAmbientContext1.ts:2:15]
+   ╭─[typescript/tests/cases/conformance/es6/yieldExpressions/generatorInAmbientContext1.ts:2:5]
  1 │ declare class C {
  2 │     *generator(): any;
-   ·               ────────
+   ·     ──────────────────
  3 │ }
    ╰────
 
   × TS(1221): Generators are not allowed in an ambient context.
-   ╭─[typescript/tests/cases/conformance/es6/yieldExpressions/generatorInAmbientContext2.ts:2:5]
+   ╭─[typescript/tests/cases/conformance/es6/yieldExpressions/generatorInAmbientContext2.ts:2:14]
  1 │ declare namespace M {
  2 │     function *generator(): any;
-   ·     ───────────────────────────
+   ·              ──────────────────
  3 │ }
    ╰────
 
   × TS(1221): Generators are not allowed in an ambient context.
-   ╭─[typescript/tests/cases/conformance/es6/yieldExpressions/generatorInAmbientContext3.d.ts:2:15]
+   ╭─[typescript/tests/cases/conformance/es6/yieldExpressions/generatorInAmbientContext3.d.ts:2:5]
  1 │ declare class C {
  2 │     *generator(): any;
-   ·               ────────
+   ·     ──────────────────
  3 │ }
    ╰────
 
   × TS(1221): Generators are not allowed in an ambient context.
-   ╭─[typescript/tests/cases/conformance/es6/yieldExpressions/generatorInAmbientContext4.d.ts:2:5]
+   ╭─[typescript/tests/cases/conformance/es6/yieldExpressions/generatorInAmbientContext4.d.ts:2:14]
  1 │ declare namespace M {
  2 │     function *generator(): any;
-   ·     ───────────────────────────
+   ·              ──────────────────
  3 │ }
    ╰────
 
@@ -20273,26 +20273,26 @@ Expect Syntax Error: tasks/coverage/typescript/tests/cases/conformance/types/wit
    ╰────
 
   × TS(1221): Generators are not allowed in an ambient context.
-   ╭─[typescript/tests/cases/conformance/es6/yieldExpressions/generatorOverloads2.ts:2:5]
+   ╭─[typescript/tests/cases/conformance/es6/yieldExpressions/generatorOverloads2.ts:2:13]
  1 │ declare namespace M {
  2 │     function* f(s: string): Iterable<any>;
-   ·     ──────────────────────────────────────
+   ·             ──────────────────────────────
  3 │     function* f(s: number): Iterable<any>;
    ╰────
 
   × TS(1221): Generators are not allowed in an ambient context.
-   ╭─[typescript/tests/cases/conformance/es6/yieldExpressions/generatorOverloads2.ts:3:5]
+   ╭─[typescript/tests/cases/conformance/es6/yieldExpressions/generatorOverloads2.ts:3:13]
  2 │     function* f(s: string): Iterable<any>;
  3 │     function* f(s: number): Iterable<any>;
-   ·     ──────────────────────────────────────
+   ·             ──────────────────────────────
  4 │     function* f(s: any): Iterable<any>;
    ╰────
 
   × TS(1221): Generators are not allowed in an ambient context.
-   ╭─[typescript/tests/cases/conformance/es6/yieldExpressions/generatorOverloads2.ts:4:5]
+   ╭─[typescript/tests/cases/conformance/es6/yieldExpressions/generatorOverloads2.ts:4:13]
  3 │     function* f(s: number): Iterable<any>;
  4 │     function* f(s: any): Iterable<any>;
-   ·     ───────────────────────────────────
+   ·             ───────────────────────────
  5 │ }
    ╰────