feat(parser): improve error message for missing block closing tokens (#15445)

Improves error message for imbalanced tokens for blocks.

**Before**
```
  × Expected `}` but found `EOF`
   ╭─[typescript/tests/cases/compiler/missingCloseBrace.ts:8:6]
 7 │
 8 │     }
   ╰────
```
**After**
```
  × Expected `}` but found `EOF`
   ╭─[typescript/tests/cases/compiler/missingCloseBrace.ts:1:22]
 1 │ function base_init() {
   ·                      ┬
   ·                      ╰── Opened here
 2 │     {
   ╰────
   ╭─[typescript/tests/cases/compiler/missingCloseBrace.ts:8:6]
 7 │
 8 │     }
   ╰────
```

Author: sapphi-red

crates/oxc_parser/src/cursor.rs

@@ -189,6 +189,21 @@ impl<'a> ParserImpl<'a> {
         self.advance(kind);
     }
 
+    #[inline]
+    pub(crate) fn expect_closing(&mut self, kind: Kind, opening_span: Span) {
+        if !self.at(kind) {
+            let range = self.cur_token().span();
+            let error = diagnostics::expect_closing(
+                kind.to_str(),
+                self.cur_kind().to_str(),
+                range,
+                opening_span,
+            );
+            self.set_fatal_error(error);
+        }
+        self.advance(kind);
+    }
+
     #[inline]
     pub(crate) fn expect_conditional_alternative(&mut self, question_span: Span) {
         if !self.at(Kind::Colon) {
@@ -382,6 +397,7 @@ impl<'a> ParserImpl<'a> {
     where
         F: Fn(&mut Self) -> T,
     {
+        let opening_span = self.cur_token().span();
         self.expect(open);
         let mut list = self.ast.vec();
         loop {
@@ -394,7 +410,7 @@ impl<'a> ParserImpl<'a> {
             }
             list.push(f(self));
         }
-        self.expect(close);
+        self.expect_closing(close, opening_span);
         list
     }
 
@@ -407,6 +423,7 @@ impl<'a> ParserImpl<'a> {
     where
         F: Fn(&mut Self) -> Option<T>,
     {
+        let opening_span = self.cur_token().span();
         self.expect(open);
         let mut list = self.ast.vec();
         loop {
@@ -419,7 +436,7 @@ impl<'a> ParserImpl<'a> {
                 break;
             }
         }
-        self.expect(close);
+        self.expect_closing(close, opening_span);
         list
     }
 

crates/oxc_parser/src/diagnostics.rs

@@ -44,6 +44,21 @@ pub fn expect_token(x0: &str, x1: &str, span: Span) -> OxcDiagnostic {
         .with_label(span.label(format!("`{x0}` expected")))
 }
 
+#[cold]
+pub fn expect_closing(
+    expected_closing: &str,
+    actual: &str,
+    span: Span,
+    opening_span: Span,
+) -> OxcDiagnostic {
+    OxcDiagnostic::error(format!("Expected `{expected_closing}` but found `{actual}`")).with_labels(
+        [
+            span.primary_label(format!("`{expected_closing}` expected")),
+            opening_span.label("Opened here"),
+        ],
+    )
+}
+
 #[cold]
 pub fn expect_closing_or_separator(
     expected_closing: &str,

crates/oxc_parser/src/js/function.rs

@@ -30,13 +30,14 @@ impl<'a> ParserImpl<'a> {
 
     pub(crate) fn parse_function_body(&mut self) -> Box<'a, FunctionBody<'a>> {
         let span = self.start_span();
+        let opening_span = self.cur_token().span();
         self.expect(Kind::LCurly);
 
         let (directives, statements) = self.context_add(Context::Return, |p| {
             p.parse_directives_and_statements(/* is_top_level */ false)
         });
 
-        self.expect(Kind::RCurly);
+        self.expect_closing(Kind::RCurly, opening_span);
         self.ast.alloc_function_body(self.end_span(span), directives, statements)
     }
 

tasks/coverage/snapshots/parser_babel.snap

@@ -1695,6 +1695,8 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
   × Expected `}` but found `EOF`
    ╭─[babel/packages/babel-parser/test/fixtures/core/uncategorised/345/input.js:1:2]
  1 │ {
+   · ┬
+   · ╰── Opened here
    ╰────
 
   × Unexpected token
@@ -1944,6 +1946,8 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ╭─[babel/packages/babel-parser/test/fixtures/core/uncategorised/386/input.js:4:2]
  3 │ 
  4 │ {
+   · ┬
+   · ╰── Opened here
    ╰────
 
   × Unexpected token
@@ -4715,6 +4719,8 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
   × Expected `}` but found `EOF`
    ╭─[babel/packages/babel-parser/test/fixtures/es2015/uncategorised/295/input.js:2:1]
  1 │ switch (cond) { case 10: let a = 20;
+   ·               ┬
+   ·               ╰── Opened here
    ╰────
 
   × Cannot assign to 'eval' in strict mode
@@ -10631,6 +10637,8 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
   × Expected `}` but found `EOF`
    ╭─[babel/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0000/input.js:2:1]
  1 │ {
+   · ┬
+   · ╰── Opened here
    ╰────
 
   × Unexpected token
@@ -11119,6 +11127,8 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
   × Expected `}` but found `EOF`
    ╭─[babel/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0069/input.js:2:1]
  1 │ {
+   · ┬
+   · ╰── Opened here
    ╰────
 
   × Unexpected token
@@ -12242,11 +12252,15 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
   × Expected `}` but found `EOF`
    ╭─[babel/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0255/input.js:2:1]
  1 │ { ;  ;
+   · ┬
+   · ╰── Opened here
    ╰────
 
   × Expected `}` but found `EOF`
    ╭─[babel/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0256/input.js:2:1]
  1 │ function t() { ;  ;
+   ·              ┬
+   ·              ╰── Opened here
    ╰────
 
   × Expected a semicolon or an implicit semicolon after a statement, but found none
@@ -12300,6 +12314,8 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
   × Expected `}` but found `EOF`
    ╭─[babel/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0266/input.js:2:1]
  1 │ class A {
+   ·         ┬
+   ·         ╰── Opened here
    ╰────
 
   × Expected `{` but found `;`
@@ -14906,6 +14922,8 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
   × Expected `}` but found `EOF`
    ╭─[babel/packages/babel-parser/test/fixtures/typescript/types-arrow-function/invalid-incomplete-object-like/input.ts:2:1]
  1 │ type F = ({
+   ·           ┬
+   ·           ╰── Opened here
    ╰────
 
   × Expected `]` but found `EOF`
@@ -14916,6 +14934,8 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
   × Expected `}` but found `EOF`
    ╭─[babel/packages/babel-parser/test/fixtures/typescript/types-arrow-function-babel-7/invalid-incomplete-object-like/input.ts:2:1]
  1 │ type F = ({
+   ·           ┬
+   ·           ╰── Opened here
    ╰────
 
   × Missing initializer in destructuring declaration

tasks/coverage/snapshots/parser_typescript.snap

@@ -8219,6 +8219,8 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
   × Expected `}` but found `EOF`
    ╭─[typescript/tests/cases/compiler/exportInFunction.ts:2:16]
  1 │ function f() {
+   ·              ┬
+   ·              ╰── Opened here
  2 │     export = 0;
    ╰────
 
@@ -9877,6 +9879,12 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
    ╰────
 
   × Expected `}` but found `EOF`
+   ╭─[typescript/tests/cases/compiler/missingCloseBrace.ts:1:22]
+ 1 │ function base_init() {
+   ·                      ┬
+   ·                      ╰── Opened here
+ 2 │     {
+   ╰────
    ╭─[typescript/tests/cases/compiler/missingCloseBrace.ts:8:6]
  7 │ 
  8 │     }
@@ -11535,6 +11543,8 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
   × Expected `}` but found `EOF`
    ╭─[typescript/tests/cases/compiler/prettyContextNotDebugAssertion.ts:1:12]
  1 │ if (true) {
+   ·           ┬
+   ·           ╰── Opened here
    ╰────
 
   × TS(2414): Class name cannot be 'any'
@@ -21663,6 +21673,13 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
 
   × Expected `}` but found `EOF`
     ╭─[typescript/tests/cases/conformance/interfaces/interfacesExtendingClasses/interfaceExtendingClass2.ts:15:6]
+  9 │ 
+ 10 │ interface I2 extends Foo { // error
+    ·                          ┬
+    ·                          ╰── Opened here
+ 11 │     a: {
+ 12 │         toString: () => {
+ 13 │             return 1;
  14 │         };
  15 │     }
     ╰────
@@ -22893,7 +22910,10 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
 
   × Expected `}` but found `EOF`
    ╭─[typescript/tests/cases/conformance/parser/ecmascript5/ErrorRecovery/AccessibilityAfterStatic/parserAccessibilityAfterStatic6.ts:3:14]
+ 1 │ class Outer
  2 │ {
+   · ┬
+   · ╰── Opened here
  3 │ static public
    ╰────
 
@@ -24232,6 +24252,8 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
   × Expected `}` but found `EOF`
    ╭─[typescript/tests/cases/conformance/parser/ecmascript5/RegressionTests/parser512084.ts:1:12]
  1 │ class foo {
+   ·           ┬
+   ·           ╰── Opened here
    ╰────
 
   × Expected `,` or `}` but found `;`