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fix(semantic): allow new.target in class field initializers #18349

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Merged
graphite-app merged 1 commit into from
Jan 21, 2026
Merged

fix(semantic): allow new.target in class field initializers #18349

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51 changes: 41 additions & 10 deletions crates/oxc_semantic/src/checker/javascript.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -512,19 +512,50 @@ pub fn check_meta_property(prop: &MetaProperty, ctx: &SemanticBuilder<'_>) {
if ctx.source_type.is_commonjs() {
return;
}
let mut in_function_scope = false;
for scope_id in ctx.scoping.scope_ancestors(ctx.current_scope_id) {
let flags = ctx.scoping.scope_flags(scope_id);
// In arrow functions, new.target is inherited from the surrounding scope.
if flags.contains(ScopeFlags::Arrow) {
continue;

// Check if we're in a valid context for new.target:
// 1. Inside a function (including constructor)
// 2. Inside a class static block
// 3. Inside a class field initializer (new.target evaluates to undefined)
//
// Arrow functions inherit new.target from their surrounding scope,
// so we skip them and continue checking the enclosing context.

let mut in_valid_context = false;

// First, check AST ancestors for class field initializers.
// We need to do this because class fields don't have their own scope.
for node_kind in ctx.nodes.ancestor_kinds(ctx.current_node_id) {
match node_kind {
// Regular functions have their own new.target binding.
// Use scope-based check from here.
AstKind::Function(_) => break,
// Class field initializers allow new.target (evaluates to undefined).
// This includes arrow functions nested inside the initializer.
AstKind::PropertyDefinition(_) | AstKind::AccessorProperty(_) => {
in_valid_context = true;
break;
}
_ => {}
}
if flags.intersects(ScopeFlags::Function | ScopeFlags::ClassStaticBlock) {
in_function_scope = true;
break;
}

// If not in a class field, fall back to scope-based check
if !in_valid_context {
for scope_id in ctx.scoping.scope_ancestors(ctx.current_scope_id) {
let flags = ctx.scoping.scope_flags(scope_id);
// In arrow functions, new.target is inherited from the surrounding scope.
if flags.contains(ScopeFlags::Arrow) {
continue;
}
if flags.intersects(ScopeFlags::Function | ScopeFlags::ClassStaticBlock) {
in_valid_context = true;
break;
}
}
}
if !in_function_scope {

if !in_valid_context {
ctx.error(diagnostics::new_target(prop.span));
}
}
Expand Down
4 changes: 3 additions & 1 deletion crates/oxc_semantic/src/diagnostics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -121,7 +121,9 @@ pub fn module_code(x0: &str, span1: Span) -> OxcDiagnostic {
#[cold]
pub fn new_target(span: Span) -> OxcDiagnostic {
OxcDiagnostic::error("Unexpected new.target expression")
.with_help("new.target is only allowed in constructors and functions invoked using the `new` operator")
.with_help(
"new.target is only allowed in constructors, functions, and class field initializers",
)
.with_label(span)
}

Expand Down
88 changes: 7 additions & 81 deletions tasks/coverage/snapshots/parser_babel.snap
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Expand Up @@ -2,7 +2,7 @@ commit: fc58af40

parser_babel Summary:
AST Parsed : 2221/2227 (99.73%)
Positive Passed: 2205/2227 (99.01%)
Positive Passed: 2206/2227 (99.06%)
Negative Passed: 1649/1689 (97.63%)
Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2026/explicit-resource-management/invalid-for-using-of-no-initializer/input.js

Expand Down Expand Up @@ -84,80 +84,6 @@ Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/ty

Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/types/invalid-import-type-options-with-spread-element/input.ts

Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2022/class-properties/new-target/input.js

× Unexpected new.target expression
╭─[babel/packages/babel-parser/test/fixtures/es2022/class-properties/new-target/input.js:2:14]
1 │ class X {
2 │ static a = new.target;
· ──────────
3 │ static b = (foo = 1 + bar(new.target));
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator

× Unexpected new.target expression
╭─[babel/packages/babel-parser/test/fixtures/es2022/class-properties/new-target/input.js:3:29]
2 │ static a = new.target;
3 │ static b = (foo = 1 + bar(new.target));
· ──────────
4 │ static c = () => new.target;
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator

× Unexpected new.target expression
╭─[babel/packages/babel-parser/test/fixtures/es2022/class-properties/new-target/input.js:4:20]
3 │ static b = (foo = 1 + bar(new.target));
4 │ static c = () => new.target;
· ──────────
5 │ static d = (foo = new.target) => {};
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator

× Unexpected new.target expression
╭─[babel/packages/babel-parser/test/fixtures/es2022/class-properties/new-target/input.js:5:21]
4 │ static c = () => new.target;
5 │ static d = (foo = new.target) => {};
· ──────────
6 │ e = new.target;
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator

× Unexpected new.target expression
╭─[babel/packages/babel-parser/test/fixtures/es2022/class-properties/new-target/input.js:6:7]
5 │ static d = (foo = new.target) => {};
6 │ e = new.target;
· ──────────
7 │ f = (foo = 1 + bar(new.target));
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator

× Unexpected new.target expression
╭─[babel/packages/babel-parser/test/fixtures/es2022/class-properties/new-target/input.js:7:22]
6 │ e = new.target;
7 │ f = (foo = 1 + bar(new.target));
· ──────────
8 │ g = () => new.target;
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator

× Unexpected new.target expression
╭─[babel/packages/babel-parser/test/fixtures/es2022/class-properties/new-target/input.js:8:13]
7 │ f = (foo = 1 + bar(new.target));
8 │ g = () => new.target;
· ──────────
9 │ h = (foo = new.target) => {};
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator

× Unexpected new.target expression
╭─[babel/packages/babel-parser/test/fixtures/es2022/class-properties/new-target/input.js:9:14]
8 │ g = () => new.target;
9 │ h = (foo = new.target) => {};
· ──────────
10 │ }
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator

Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2022/class-static-block/duplicate-function-var-name/input.js

× Identifier `x` has already been declared
Expand Down Expand Up @@ -956,14 +882,14 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
1 │ const x = new.target;
· ──────────
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator
help: new.target is only allowed in constructors, functions, and class field initializers

× Unexpected new.target expression
╭─[babel/packages/babel-parser/test/fixtures/core/opts/allowNewTargetOutsideFunction-false-2/input.js:1:17]
1 │ const y = () => new.target;
· ──────────
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator
help: new.target is only allowed in constructors, functions, and class field initializers

× TS(1108): A 'return' statement can only be used within a function body.
╭─[babel/packages/babel-parser/test/fixtures/core/opts/allowReturnOutsideFunction-true-invalid-in-static-block/input.js:3:5]
Expand Down Expand Up @@ -3132,7 +3058,7 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
· ──────────
3 │ }
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator
help: new.target is only allowed in constructors, functions, and class field initializers

× The only valid meta property for new is new.target
╭─[babel/packages/babel-parser/test/fixtures/es2015/meta-properties/new-invalid-prop/input.js:2:3]
Expand All @@ -3147,7 +3073,7 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
1 │ new.target
· ──────────
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator
help: new.target is only allowed in constructors, functions, and class field initializers

× Keywords cannot contain escape characters
╭─[babel/packages/babel-parser/test/fixtures/es2015/meta-properties/new-target-invalid-escaped-new/input.js:1:16]
Expand Down Expand Up @@ -8250,7 +8176,7 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
1 │ var x = new.target;
· ──────────
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator
help: new.target is only allowed in constructors, functions, and class field initializers

× Expected `(` but found `}`
╭─[babel/packages/babel-parser/test/fixtures/es2022/class-properties/no-ctor/input.js:3:1]
Expand Down Expand Up @@ -9953,7 +9879,7 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
1 │ var x = new.target;
· ──────────
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator
help: new.target is only allowed in constructors, functions, and class field initializers

× The only valid meta property for new is new.target
╭─[babel/packages/babel-parser/test/fixtures/esprima/es2015-meta-property/unknown-property/input.js:1:22]
Expand Down
6 changes: 3 additions & 3 deletions tasks/coverage/snapshots/parser_test262.snap
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Expand Up @@ -20523,15 +20523,15 @@ Negative Passed: 4581/4581 (100.00%)
· ──────────
38 │ };
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator
help: new.target is only allowed in constructors, functions, and class field initializers

× Unexpected new.target expression
╭─[test262/test/language/global-code/new.target.js:21:1]
20 │
21 │ new.target;
· ──────────
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator
help: new.target is only allowed in constructors, functions, and class field initializers

× TS(1108): A 'return' statement can only be used within a function body.
╭─[test262/test/language/global-code/return.js:23:1]
Expand Down Expand Up @@ -24730,7 +24730,7 @@ Negative Passed: 4581/4581 (100.00%)
16 │ new.target;
· ──────────
╰────
help: new.target is only allowed in constructors and functions invoked using the `new` operator
help: new.target is only allowed in constructors, functions, and class field initializers

× The keyword 'public' is reserved
╭─[test262/test/language/module-code/early-strict-mode.js:15:5]
Expand Down
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