feat(linter): add no-redeclare rule. (#683)

Close: #615 #520 
Rule: [Docs](https://eslint.org/docs/latest/rules/no-redeclare)

crates/oxc_linter/src/rules.rs

@@ -64,6 +64,7 @@ mod eslint {
     pub mod no_new_symbol;
     pub mod no_obj_calls;
     pub mod no_prototype_builtins;
+    pub mod no_redeclare;
     pub mod no_return_await;
     pub mod no_self_assign;
     pub mod no_self_compare;
@@ -171,6 +172,7 @@ oxc_macros::declare_all_lint_rules! {
     eslint::no_new_symbol,
     eslint::no_obj_calls,
     eslint::no_prototype_builtins,
+    eslint::no_redeclare,
     eslint::no_return_await,
     eslint::no_self_assign,
     eslint::no_self_compare,

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

@@ -0,0 +1,179 @@
+use oxc_ast::{
+    ast::{BindingIdentifier, BindingPatternKind},
+    AstKind,
+};
+use oxc_diagnostics::{
+    miette::{self, Diagnostic},
+    thiserror::{self, Error},
+};
+use oxc_macros::declare_oxc_lint;
+use oxc_semantic::VariableInfo;
+use oxc_span::{Atom, Span};
+
+use crate::{context::LintContext, globals::BUILTINS, rule::Rule};
+
+#[derive(Debug, Error, Diagnostic)]
+#[error("eslint(no-redeclare): '{0}' is already defined.")]
+#[diagnostic(severity(warning))]
+struct NoRedeclareDiagnostic(
+    Atom,
+    #[label("'{0}' is already defined.")] pub Span,
+    #[label("It can not be redeclare here.")] pub Span,
+);
+
+#[derive(Debug, Error, Diagnostic)]
+#[error("eslint(no-redeclare): '{0}' is already defined as a built-in global variable.")]
+#[diagnostic(severity(warning))]
+struct NoRedeclareAsBuiltiInDiagnostic(
+    Atom,
+    #[label("'{0}' is already defined as a built-in global variable.")] pub Span,
+);
+
+#[derive(Debug, Error, Diagnostic)]
+#[error("eslint(no-redeclare): '{0}' is already defined by a variable declaration.")]
+#[diagnostic(severity(warning))]
+struct NoRedeclareBySyntaxDiagnostic(
+    Atom,
+    #[label("'{0}' is already defined by a variable declaration.")] pub Span,
+    #[label("It can not be redeclare here.")] pub Span,
+);
+
+#[derive(Debug, Default, Clone)]
+pub struct NoRedeclare {
+    built_in_globals: bool,
+}
+
+declare_oxc_lint!(
+    /// ### What it does
+    ///
+    /// Disallow variable redeclaration
+    ///
+    /// ### Why is this bad?
+    ///
+    /// n JavaScript, it’s possible to redeclare the same variable name using var. This can lead to confusion as to where the variable is actually declared and initialized.
+    ///
+    /// ### Example
+    /// ```javascript
+    /// var a = 3;
+    /// var a = 10;
+    /// ```
+    NoRedeclare,
+    correctness
+);
+
+impl Rule for NoRedeclare {
+    fn from_configuration(value: serde_json::Value) -> Self {
+        let built_in_globals = value
+            .get(0)
+            .and_then(|config| config.get("builtinGlobals"))
+            .and_then(serde_json::Value::as_bool)
+            .unwrap_or(false);
+
+        Self { built_in_globals }
+    }
+
+    fn run_once(&self, ctx: &LintContext) {
+        let redeclare_variables = ctx.semantic().redeclare_variables();
+        let symbol_table = ctx.semantic().symbols();
+
+        for variable in redeclare_variables {
+            let decl = symbol_table.get_declaration(variable.symbol_id);
+            match ctx.nodes().kind(decl) {
+                AstKind::VariableDeclarator(var) => {
+                    if let BindingPatternKind::BindingIdentifier(ident) = &var.id.kind {
+                        self.report_diagnostic(ctx, variable, ident);
+                    }
+                }
+                AstKind::FormalParameters(params) => {
+                    for item in &params.items {
+                        if let BindingPatternKind::BindingIdentifier(ident) = &item.pattern.kind {
+                            self.report_diagnostic(ctx, variable, ident);
+                        }
+                    }
+                }
+                _ => {}
+            }
+        }
+    }
+}
+
+impl NoRedeclare {
+    fn report_diagnostic(
+        &self,
+        ctx: &LintContext,
+        variable: &VariableInfo,
+        ident: &BindingIdentifier,
+    ) {
+        if self.built_in_globals && BUILTINS.get(&ident.name).is_some() {
+            ctx.diagnostic(NoRedeclareAsBuiltiInDiagnostic(ident.name.clone(), ident.span));
+        } else if variable.name == ident.name && variable.span != ident.span {
+            ctx.diagnostic(NoRedeclareDiagnostic(ident.name.clone(), ident.span, variable.span));
+        }
+    }
+}
+
+#[test]
+fn test() {
+    use crate::tester::Tester;
+
+    let pass = vec![
+        ("var a = 3; var b = function() { var a = 10; };", None),
+        ("var a = 3; a = 10;", None),
+        ("if (true) {\n    let b = 2;\n} else {    \nlet b = 3;\n}", None),
+        ("var a; class C { static { var a; } }", None),
+        ("class C { static { var a; } } var a; ", None),
+        ("function a(){} class C { static { var a; } }", None),
+        ("var a; class C { static { function a(){} } }", None),
+        ("class C { static { var a; } static { var a; } }", None),
+        ("class C { static { function a(){} } static { function a(){} } }", None),
+        ("class C { static { var a; { function a(){} } } }", None),
+        ("class C { static { function a(){}; { function a(){} } } }", None),
+        ("class C { static { var a; { let a; } } }", None),
+        ("class C { static { let a; { let a; } } }", None),
+        ("class C { static { { let a; } { let a; } } }", None),
+        ("var Object = 0;", Some(serde_json::json!([{ "builtinGlobals": false }]))),
+        ("var Object = 0;", Some(serde_json::json!([{ "builtinGlobals": false }]))),
+        ("var Object = 0;", Some(serde_json::json!([{ "builtinGlobals": false }]))),
+        ("var top = 0;", Some(serde_json::json!([{ "builtinGlobals": false }]))),
+        ("var top = 0;", Some(serde_json::json!([{ "builtinGlobals": false }]))),
+        ("var top = 0;", Some(serde_json::json!([{ "builtinGlobals": false }]))),
+        ("var self = 1", Some(serde_json::json!([{ "builtinGlobals": false }]))),
+        ("var globalThis = foo", Some(serde_json::json!([{ "builtinGlobals": false }]))),
+        ("var globalThis = foo", Some(serde_json::json!([{ "builtinGlobals": false }]))),
+    ];
+
+    let fail = vec![
+        ("switch(foo) { case a: var b = 3;\ncase b: var b = 4}", None),
+        ("var a = 3; var a = 10;", None),
+        ("var a = {}; var a = [];", None),
+        ("var a; function a() {}", None),
+        ("function a() {} function a() {}", None),
+        ("var a = function() { }; var a = function() { }", None),
+        ("var a = function() { }; var a = new Date();", None),
+        ("var a = 3; var a = 10; var a = 15;", None),
+        ("var a; var a;", None),
+        ("export var a; var a;", None),
+        // `var` redeclaration in class static blocks. Redeclaration of functions is not allowed in class static blocks.
+        ("class C { static { var a; var a; } }", None),
+        // Todo: Fix me
+        // ("class C { static { var a; { var a; } } }", None),
+        // ("class C { static { { var a; } var a; } }", None),
+        // ("class C { static { { var a; } { var a; } } }", None),
+        // ("var Object = 0;", Some(serde_json::json!([{ "builtinGlobals": true }]))),
+        (
+            "var a; var {a = 0, b: Object = 0} = {};",
+            Some(serde_json::json!([{ "builtinGlobals": true }])),
+        ),
+        // ("var globalThis = 0;", Some(serde_json::json!([{ "builtinGlobals": true }]))),
+        (
+            "var a; var {a = 0, b: globalThis = 0} = {};",
+            Some(serde_json::json!([{ "builtinGlobals": true }])),
+        ),
+        ("function f() { var a; var a; }", None),
+        ("function f(a) { var a; }", None),
+        // ("function f() { var a; if (test) { var a; } }", None),
+        ("for (var a, a;;);", None),
+    ];
+
+    Tester::new(NoRedeclare::NAME, pass, fail).test_and_snapshot();
+}

crates/oxc_linter/src/snapshots/no_redeclare.snap

@@ -0,0 +1,162 @@
+---
+source: crates/oxc_linter/src/tester.rs
+assertion_line: 105
+expression: no_redeclare
+---
+  ⚠ eslint(no-redeclare): 'b' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ switch(foo) { case a: var b = 3;
+   ·                           ┬
+   ·                           ╰── 'b' is already defined.
+ 2 │ case b: var b = 4}
+   ·             ┬
+   ·             ╰── It can not be redeclare here.
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'b' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ switch(foo) { case a: var b = 3;
+   ·                           ┬
+   ·                           ╰── 'b' is already defined.
+ 2 │ case b: var b = 4}
+   ·             ┬
+   ·             ╰── It can not be redeclare here.
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'a' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ var a = 3; var a = 10;
+   ·     ┬          ┬
+   ·     │          ╰── It can not be redeclare here.
+   ·     ╰── 'a' is already defined.
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'a' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ var a = {}; var a = [];
+   ·     ┬           ┬
+   ·     │           ╰── It can not be redeclare here.
+   ·     ╰── 'a' is already defined.
+   ╰────
+
+  × Identifier `a` has already been declared
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ var a; function a() {}
+   ·     ┬           ┬
+   ·     │           ╰── It can not be redeclared here
+   ·     ╰── `a` has already been declared here
+   ╰────
+
+  × Identifier `a` has already been declared
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ function a() {} function a() {}
+   ·          ┬               ┬
+   ·          │               ╰── It can not be redeclared here
+   ·          ╰── `a` has already been declared here
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'a' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ var a = function() { }; var a = function() { }
+   ·     ┬                       ┬
+   ·     │                       ╰── It can not be redeclare here.
+   ·     ╰── 'a' is already defined.
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'a' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ var a = function() { }; var a = new Date();
+   ·     ┬                       ┬
+   ·     │                       ╰── It can not be redeclare here.
+   ·     ╰── 'a' is already defined.
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'a' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ var a = 3; var a = 10; var a = 15;
+   ·     ┬          ┬
+   ·     │          ╰── It can not be redeclare here.
+   ·     ╰── 'a' is already defined.
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'a' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ var a = 3; var a = 10; var a = 15;
+   ·     ┬                      ┬
+   ·     │                      ╰── It can not be redeclare here.
+   ·     ╰── 'a' is already defined.
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'a' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ var a; var a;
+   ·     ┬      ┬
+   ·     │      ╰── It can not be redeclare here.
+   ·     ╰── 'a' is already defined.
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'a' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ export var a; var a;
+   ·            ┬      ┬
+   ·            │      ╰── It can not be redeclare here.
+   ·            ╰── 'a' is already defined.
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'a' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ class C { static { var a; var a; } }
+   ·                        ┬      ┬
+   ·                        │      ╰── It can not be redeclare here.
+   ·                        ╰── 'a' is already defined.
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'a' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ var a; var {a = 0, b: Object = 0} = {};
+   ·     ┬       ┬
+   ·     │       ╰── It can not be redeclare here.
+   ·     ╰── 'a' is already defined.
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'a' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ var a; var {a = 0, b: globalThis = 0} = {};
+   ·     ┬       ┬
+   ·     │       ╰── It can not be redeclare here.
+   ·     ╰── 'a' is already defined.
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'a' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ function f() { var a; var a; }
+   ·                    ┬      ┬
+   ·                    │      ╰── It can not be redeclare here.
+   ·                    ╰── 'a' is already defined.
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'a' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ function f(a) { var a; }
+   ·            ┬        ┬
+   ·            │        ╰── It can not be redeclare here.
+   ·            ╰── 'a' is already defined.
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'a' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ for (var a, a;;);
+   ·          ┬  ┬
+   ·          │  ╰── It can not be redeclare here.
+   ·          ╰── 'a' is already defined.
+   ╰────
+
+  ⚠ eslint(no-redeclare): 'a' is already defined.
+   ╭─[no_redeclare.tsx:1:1]
+ 1 │ for (var a, a;;);
+   ·          ┬  ┬
+   ·          │  ╰── It can not be redeclare here.
+   ·          ╰── 'a' is already defined.
+   ╰────
+
+

crates/oxc_semantic/src/binder.rs

@@ -5,7 +5,7 @@ use oxc_ast::ast::*;
 use oxc_ast::{syntax_directed_operations::BoundNames, AstKind};
 use oxc_span::{Atom, SourceType};
 
-use crate::{scope::ScopeFlags, symbol::SymbolFlags, SemanticBuilder};
+use crate::{scope::ScopeFlags, symbol::SymbolFlags, SemanticBuilder, VariableInfo};
 
 pub trait Binder {
     fn bind(&self, _builder: &mut SemanticBuilder) {}
@@ -49,6 +49,12 @@ impl<'a> Binder for VariableDeclarator<'a> {
                             .scope
                             .get_bindings_mut(scope_id)
                             .insert(ident.name.clone(), symbol_id);
+                    } else {
+                        builder.add_redeclared_variables(VariableInfo {
+                            name: ident.name.clone(),
+                            span: ident.span,
+                            symbol_id,
+                        });
                     }
                 }
             }

crates/oxc_semantic/src/builder.rs

@@ -35,6 +35,18 @@ struct UnusedLabels<'a> {
     labels: Vec<AstNodeId>,
 }
 
+#[derive(Debug, Clone)]
+pub struct VariableInfo {
+    pub name: Atom,
+    pub span: Span,
+    pub symbol_id: SymbolId,
+}
+
+#[derive(Debug)]
+pub struct RedeclareVariables {
+    pub variables: Vec<VariableInfo>,
+}
+
 pub struct SemanticBuilder<'a> {
     pub source_text: &'a str,
 
@@ -70,6 +82,8 @@ pub struct SemanticBuilder<'a> {
     jsdoc: JSDocBuilder<'a>,
 
     check_syntax_error: bool,
+
+    redeclare_variables: RedeclareVariables,
 }
 
 pub struct SemanticBuilderReturn<'a> {
@@ -101,6 +115,7 @@ impl<'a> SemanticBuilder<'a> {
             unused_labels: UnusedLabels { scopes: vec![], curr_scope: 0, labels: vec![] },
             jsdoc: JSDocBuilder::new(source_text, &trivias),
             check_syntax_error: false,
+            redeclare_variables: RedeclareVariables { variables: vec![] },
         }
     }
 
@@ -155,6 +170,7 @@ impl<'a> SemanticBuilder<'a> {
             module_record: Arc::clone(&self.module_record),
             jsdoc: self.jsdoc.build(),
             unused_labels: self.unused_labels.labels,
+            redeclare_variables: self.redeclare_variables.variables,
         };
         SemanticBuilderReturn { semantic, errors: self.errors.into_inner() }
     }
@@ -170,6 +186,7 @@ impl<'a> SemanticBuilder<'a> {
             module_record: Arc::new(ModuleRecord::default()),
             jsdoc: self.jsdoc.build(),
             unused_labels: self.unused_labels.labels,
+            redeclare_variables: self.redeclare_variables.variables,
         }
     }
 
@@ -251,6 +268,7 @@ impl<'a> SemanticBuilder<'a> {
     ) -> SymbolId {
         if let Some(symbol_id) = self.check_redeclaration(scope_id, span, name, excludes, true) {
             self.symbols.union_flag(symbol_id, includes);
+            self.add_redeclared_variables(VariableInfo { name: name.clone(), span, symbol_id });
             return symbol_id;
         }
 
@@ -321,7 +339,8 @@ impl<'a> SemanticBuilder<'a> {
         report_error: bool,
     ) -> Option<SymbolId> {
         let symbol_id = self.scope.get_binding(scope_id, name)?;
-        if report_error && self.symbols.get_flag(symbol_id).intersects(excludes) {
+        let flag = self.symbols.get_flag(symbol_id);
+        if report_error && flag.intersects(excludes) {
             let symbol_span = self.symbols.get_span(symbol_id);
             self.error(Redeclaration(name.clone(), symbol_span, span));
         }
@@ -414,6 +433,10 @@ impl<'a> SemanticBuilder<'a> {
             }
         }
     }
+
+    pub fn add_redeclared_variables(&mut self, variable: VariableInfo) {
+        self.redeclare_variables.variables.push(variable);
+    }
 }
 
 impl<'a> Visit<'a> for SemanticBuilder<'a> {

crates/oxc_semantic/src/lib.rs

@@ -22,6 +22,7 @@ pub use oxc_syntax::{
 };
 
 pub use crate::{
+    builder::VariableInfo,
     node::{AstNode, AstNodeId, AstNodes, NodeFlags},
     reference::{Reference, ReferenceFlag, ReferenceId},
     scope::ScopeTree,
@@ -46,6 +47,8 @@ pub struct Semantic<'a> {
     jsdoc: JSDoc<'a>,
 
     unused_labels: Vec<AstNodeId>,
+
+    redeclare_variables: Vec<VariableInfo>,
 }
 
 impl<'a> Semantic<'a> {
@@ -117,6 +120,10 @@ impl<'a> Semantic<'a> {
     pub fn is_reference_to_global_variable(&self, ident: &IdentifierReference) -> bool {
         self.scopes().root_unresolved_references().contains_key(&ident.name)
     }
+
+    pub fn redeclare_variables(&self) -> &Vec<VariableInfo> {
+        &self.redeclare_variables
+    }
 }
 
 #[cfg(test)]