feat(linter/eslint): Implement no-label-var (#4087)

Rule Detail:
[link](https://eslint.org/docs/latest/rules/no-label-var)

Co-authored-by: Don Isaac <donald.isaac@gmail.com>

crates/oxc_linter/src/rules.rs

@@ -75,6 +75,7 @@ mod eslint {
     pub mod no_inner_declarations;
     pub mod no_irregular_whitespace;
     pub mod no_iterator;
+    pub mod no_label_var;
     pub mod no_loss_of_precision;
     pub mod no_multi_str;
     pub mod no_new;
@@ -452,6 +453,7 @@ oxc_macros::declare_all_lint_rules! {
     eslint::no_case_declarations,
     eslint::no_class_assign,
     eslint::no_multi_str,
+    eslint::no_label_var,
     eslint::require_await,
     eslint::no_compare_neg_zero,
     eslint::no_cond_assign,

crates/oxc_linter/src/rules/eslint/no_label_var.rs

@@ -0,0 +1,79 @@
+use oxc_ast::AstKind;
+use oxc_diagnostics::OxcDiagnostic;
+use oxc_macros::declare_oxc_lint;
+use oxc_span::Span;
+
+use crate::{context::LintContext, rule::Rule, AstNode};
+
+fn no_label_var_diagnostic(x0: &str, span0: Span, span1: Span) -> OxcDiagnostic {
+    OxcDiagnostic::warn(format!(
+        "eslint(no-label-var): Found identifier '{x0}' with the same name as a label."
+    ))
+    .with_labels([
+        span0.label(format!("Identifier '{x0}' found here.")),
+        span1.label("Label with the same name."),
+    ])
+}
+
+#[derive(Debug, Default, Clone)]
+pub struct NoLabelVar;
+
+declare_oxc_lint!(
+    /// ### What it does
+    ///
+    /// Disallow labels that share a name with a variable.
+    ///
+    /// ### Why is this bad?
+    ///
+    /// This rule aims to create clearer code by disallowing the bad practice of creating a label
+    /// that shares a name with a variable that is in scope.
+    ///
+    /// ### Example
+    /// ```javascript
+    /// var x = foo;
+    /// function bar() {
+    /// x:
+    ///   for (;;) {
+    ///     break x;
+    ///   }
+    /// }
+    /// ```
+    NoLabelVar,
+    style,
+);
+
+impl Rule for NoLabelVar {
+    fn run<'a>(&self, node: &AstNode<'a>, ctx: &LintContext<'a>) {
+        let AstKind::LabeledStatement(labeled_stmt) = node.kind() else { return };
+
+        if let Some(symbol_id) =
+            ctx.scopes().find_binding(node.scope_id(), &labeled_stmt.label.name)
+        {
+            let decl_span = ctx.symbols().get_span(symbol_id);
+            let label_decl = labeled_stmt.span.start;
+            ctx.diagnostic(no_label_var_diagnostic(
+                &labeled_stmt.label.name,
+                decl_span,
+                Span::new(label_decl, label_decl + 1),
+            ));
+        }
+    }
+}
+
+#[test]
+fn test() {
+    use crate::tester::Tester;
+
+    let pass = vec![
+        "function bar() { q: for(;;) { break q; } } function foo () { var q = t; }",
+        "function bar() { var x = foo; q: for(;;) { break q; } }",
+    ];
+
+    let fail = vec![
+        "var x = foo; function bar() { x: for(;;) { break x; } }",
+        "function bar() { var x = foo; x: for(;;) { break x; } }",
+        "function bar(x) { x: for(;;) { break x; } }",
+    ];
+
+    Tester::new(NoLabelVar::NAME, pass, fail).test_and_snapshot();
+}

crates/oxc_linter/src/snapshots/no_label_var.snap

@@ -0,0 +1,26 @@
+---
+source: crates/oxc_linter/src/tester.rs
+---
+  ⚠ eslint(no-label-var): Found identifier 'x' with the same name as a label.
+   ╭─[no_label_var.tsx:1:5]
+ 1 │ var x = foo; function bar() { x: for(;;) { break x; } }
+   ·     ┬                         ┬
+   ·     │                         ╰── Label with the same name.
+   ·     ╰── Identifier 'x' found here.
+   ╰────
+
+  ⚠ eslint(no-label-var): Found identifier 'x' with the same name as a label.
+   ╭─[no_label_var.tsx:1:22]
+ 1 │ function bar() { var x = foo; x: for(;;) { break x; } }
+   ·                      ┬        ┬
+   ·                      │        ╰── Label with the same name.
+   ·                      ╰── Identifier 'x' found here.
+   ╰────
+
+  ⚠ eslint(no-label-var): Found identifier 'x' with the same name as a label.
+   ╭─[no_label_var.tsx:1:14]
+ 1 │ function bar(x) { x: for(;;) { break x; } }
+   ·              ┬    ┬
+   ·              │    ╰── Label with the same name.
+   ·              ╰── Identifier 'x' found here.
+   ╰────