fix(parser): report abstract private field error on modifier (#27314)

For `abstract #quux = 3`, report TS18019 on the `abstract` keyword instead of the private identifier, matching TypeScript. Keep the boolean check on the fast path and retrieve the modifier span only when reporting the error.

crates/oxc_parser/src/js/class.rs

@@ -797,7 +797,8 @@ impl<'a, C: Config> ParserImpl<'a, C> {
             }
         }
         if r#abstract && name.is_private_identifier() {
-            self.error(diagnostics::abstract_with_private_identifier(name.span()));
+            let modifier = modifiers.get(ModifierKind::Abstract).unwrap();
+            self.error(diagnostics::abstract_with_private_identifier(modifier.span()));
         }
         if r#abstract && initializer.is_some() {
             let (name, span) = self.abstract_member_name(&name);

tasks/coverage/snapshots/parser_babel.snap

@@ -12459,10 +12459,10 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
   help: Try inserting a semicolon here
 
   × TS(18019): 'abstract' modifier cannot be used with a private identifier.
-   ╭─[babel/packages/babel-parser/test/fixtures/estree/class-private-property/typescript-invalid-abstract/input.ts:2:12]
+   ╭─[babel/packages/babel-parser/test/fixtures/estree/class-private-property/typescript-invalid-abstract/input.ts:2:3]
  1 │ abstract class TSAbstractClass {
  2 │   abstract #foo: boolean;
-   ·            ────
+   ·   ────────
  3 │ }
    ╰────
 
@@ -13722,10 +13722,10 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
     ╰────
 
   × TS(18019): 'abstract' modifier cannot be used with a private identifier.
-   ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/private-fields-modifier-abstract/input.ts:2:12]
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/private-fields-modifier-abstract/input.ts:2:3]
  1 │ abstract class A {
  2 │   abstract #a;
-   ·            ──
+   ·   ────────
  3 │ }
    ╰────
 

tasks/coverage/snapshots/parser_typescript.snap

@@ -18261,10 +18261,10 @@ Expect to Parse: tasks/coverage/typescript/tsc/testdata/tests/cases/conformance/
     ╰────
 
   × TS(18019): 'abstract' modifier cannot be used with a private identifier.
-    ╭─[typescript/tsc/testdata/tests/cases/conformance/classes/members/privateNames/privateNamesIncompatibleModifiers.ts:32:14]
+    ╭─[typescript/tsc/testdata/tests/cases/conformance/classes/members/privateNames/privateNamesIncompatibleModifiers.ts:32:5]
  31 │ abstract class B {
  32 │     abstract #quux = 3;      // Error
-    ·              ─────
+    ·     ────────
  33 │ }
     ╰────