feat(parser): improve trailing comma error messages

crates/oxc_parser/src/diagnostics.rs

@@ -44,6 +44,13 @@ pub fn expect_token(x0: &str, x1: &str, span: Span) -> OxcDiagnostic {
         .with_label(span.label(format!("`{x0}` expected")))
 }
 
+#[cold]
+pub fn unexpected_trailing_comma(name: &'static str, span: Span) -> OxcDiagnostic {
+    OxcDiagnostic::error(format!("{name} may not have a trailing comma."))
+        .with_label(span)
+        .with_help("Remove the trailing comma here")
+}
+
 #[cold]
 pub fn invalid_escape_sequence(span: Span) -> OxcDiagnostic {
     OxcDiagnostic::error("Invalid escape sequence").with_label(span)
@@ -236,9 +243,7 @@ pub fn spread_last_element(span: Span) -> OxcDiagnostic {
 
 #[cold]
 pub fn rest_element_trailing_comma(span: Span) -> OxcDiagnostic {
-    OxcDiagnostic::error("A rest parameter or binding pattern may not have a trailing comma.")
-        .with_label(span)
-        .with_help("Remove the trailing comma here")
+    unexpected_trailing_comma("A rest parameter or binding pattern", span)
 }
 
 #[cold]

crates/oxc_parser/src/js/expression.rs

@@ -217,7 +217,10 @@ impl<'a> ParserImpl<'a> {
         });
 
         if let Some(comma_span) = comma_span {
-            let error = diagnostics::expect_token(")", ",", self.end_span(comma_span));
+            let error = diagnostics::unexpected_trailing_comma(
+                "Parenthesized expressions",
+                self.end_span(comma_span),
+            );
             return self.fatal_error(error);
         }
 

crates/oxc_parser/src/ts/types.rs

@@ -1222,7 +1222,10 @@ impl<'a> ParserImpl<'a> {
             Self::parse_ts_index_signature_name,
         );
         if let Some(comma_span) = comma_span {
-            self.error(diagnostics::expect_token("]", ",", self.end_span(comma_span)));
+            self.error(diagnostics::unexpected_trailing_comma(
+                "Index signature declarations",
+                self.end_span(comma_span),
+            ));
         }
         self.expect(Kind::RBrack);
         if params.len() != 1 {

tasks/coverage/snapshots/parser_babel.snap

@@ -5912,12 +5912,12 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ·              ─
    ╰────
 
-  × Expected `)` but found `,`
+  × Parenthesized expressions may not have a trailing comma.
    ╭─[babel/packages/babel-parser/test/fixtures/es2017/trailing-function-commas/7/input.js:1:7]
  1 │ ('foo',)
-   ·       ┬
-   ·       ╰── `)` expected
+   ·       ─
    ╰────
+  help: Remove the trailing comma here
 
   × `await` is only allowed within async functions and at the top levels of modules
    ╭─[babel/packages/babel-parser/test/fixtures/es2018/async-generators/for-await-async-context/input.js:2:7]

tasks/coverage/snapshots/parser_typescript.snap

@@ -8738,32 +8738,32 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
  3 │ }
    ╰────
 
-  × Expected `]` but found `,`
+  × Index signature declarations may not have a trailing comma.
    ╭─[typescript/tests/cases/compiler/indexSignatureWithTrailingComma.ts:2:17]
  1 │ type A = {
  2 │     [key: string,]: string;
-   ·                 ┬
-   ·                 ╰── `]` expected
+   ·                 ─
  3 │ };
    ╰────
+  help: Remove the trailing comma here
 
-  × Expected `]` but found `,`
+  × Index signature declarations may not have a trailing comma.
    ╭─[typescript/tests/cases/compiler/indexSignatureWithTrailingComma.ts:6:17]
  5 │ interface B {
  6 │     [key: string,]: string;
-   ·                 ┬
-   ·                 ╰── `]` expected
+   ·                 ─
  7 │ }
    ╰────
+  help: Remove the trailing comma here
 
-  × Expected `]` but found `,`
+  × Index signature declarations may not have a trailing comma.
     ╭─[typescript/tests/cases/compiler/indexSignatureWithTrailingComma.ts:10:17]
   9 │ class C {
  10 │     [key: string,]: null;
-    ·                 ┬
-    ·                 ╰── `]` expected
+    ·                 ─
  11 │ }
     ╰────
+  help: Remove the trailing comma here
 
   × TS(1021): An index signature must have a type annotation.
    ╭─[typescript/tests/cases/compiler/indexSignatureWithoutTypeAnnotation1.ts:2:3]
@@ -20386,14 +20386,14 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
  8 │         this += value;
    ╰────
 
-  × Expected `)` but found `,`
+  × Parenthesized expressions may not have a trailing comma.
     ╭─[typescript/tests/cases/conformance/expressions/commaOperator/commaOperatorWithoutOperand.ts:9:5]
   8 │ // Missing the second operand
   9 │ (ANY, );
-    ·     ┬
-    ·     ╰── `)` expected
+    ·     ─
  10 │ (BOOLEAN, );
     ╰────
+  help: Remove the trailing comma here
 
   × 'with' statements are not allowed
    ╭─[typescript/tests/cases/conformance/expressions/functions/arrowFunctionContexts.ts:2:1]

tasks/track_memory_allocations/allocs_parser.snap

@@ -2,7 +2,7 @@ File                       | File size      || Sys allocs     | Sys reallocs   |
 -------------------------------------------------------------------------------------------------------------------------------------------
 checker.ts                 | 2.92 MB        ||          10165 |             21 ||         268665 |          23341
 
-cal.com.tsx                | 1.06 MB        ||           2209 |             61 ||         138188 |          13712
+cal.com.tsx                | 1.06 MB        ||           2210 |             62 ||         138188 |          13712
 
 RadixUIAdoptionSection.jsx | 2.52 kB        ||              1 |              0 ||            365 |             66