refactor(semantic): align handling of declaring symbol for function with TypeScript

crates/oxc_linter/src/snapshots/eslint_no_redeclare.snap

@@ -35,12 +35,12 @@ source: crates/oxc_linter/src/tester.rs
    ·     ╰── `a` has already been declared here
    ╰────
 
-  × Identifier `a` has already been declared
+  ⚠ eslint(no-redeclare): 'a' is already defined.
    ╭─[no_redeclare.tsx:1:10]
  1 │ function a() {} function a() {}
    ·          ┬               ┬
-   ·          │               ╰── It can not be redeclared here
-   ·          ╰── `a` has already been declared here
+   ·          │               ╰── It can not be redeclare here.
+   ·          ╰── 'a' is already defined.
    ╰────
 
   ⚠ eslint(no-redeclare): 'a' is already defined.

crates/oxc_semantic/src/binder.rs

@@ -4,7 +4,7 @@ use std::ptr;
 
 use oxc_ast::{AstKind, ast::*};
 use oxc_ecmascript::{BoundNames, IsSimpleParameterList};
-use oxc_span::{GetSpan, SourceType};
+use oxc_span::GetSpan;
 use oxc_syntax::{
     scope::{ScopeFlags, ScopeId},
     symbol::SymbolFlags,
@@ -133,24 +133,6 @@ impl<'a> Binder<'a> for Class<'a> {
     }
 }
 
-// It is a Syntax Error if the LexicallyDeclaredNames of StatementList contains any duplicate entries,
-// unless the source text matched by this production is not strict mode code
-// and the duplicate entries are only bound by FunctionDeclarations.
-// https://tc39.es/ecma262/#sec-block-level-function-declarations-web-legacy-compatibility-semantics
-fn function_as_var(flags: ScopeFlags, source_type: SourceType) -> bool {
-    flags.is_function() || (source_type.is_script() && flags.is_top())
-}
-
-/// Check if the function is not allowed to be redeclared.
-pub fn is_function_redeclared_not_allowed(
-    func: &Function<'_>,
-    builder: &SemanticBuilder<'_>,
-) -> bool {
-    let current_scope_flags = builder.current_scope_flags();
-    (current_scope_flags.is_strict_mode() || func.r#async || func.generator)
-        && !function_as_var(current_scope_flags, builder.source_type)
-}
-
 /// Check for Annex B `if (foo) function a() {} else function b() {}`
 fn is_function_part_of_if_statement(function: &Function, builder: &SemanticBuilder) -> bool {
     if builder.current_scope_flags().is_strict_mode() {
@@ -189,29 +171,18 @@ impl<'a> Binder<'a> for Function<'a> {
                 );
                 ident.symbol_id.set(Some(symbol_id));
             } else {
-                let excludes = if self.is_declaration() {
-                    // The visitor is already inside the function scope,
-                    // retrieve the parent scope for the function id to bind to.
-                    if is_function_redeclared_not_allowed(self, builder) {
-                        SymbolFlags::BlockScopedVariableExcludes
-                    } else {
-                        SymbolFlags::FunctionScopedVariableExcludes
-                    }
-                } else if self.is_expression() {
-                    // https://tc39.es/ecma262/#sec-runtime-semantics-instantiateordinaryfunctionexpression
-                    // 5. Perform ! funcEnv.CreateImmutableBinding(name, false).
-                    SymbolFlags::empty()
-                } else {
-                    unreachable!(
-                        "Currently we haven't create a symbol for typescript syntax function"
-                    );
-                };
-
                 let symbol_id = builder.declare_symbol(
                     ident.span,
                     &ident.name,
                     SymbolFlags::Function,
-                    excludes,
+                    if builder.source_type.is_typescript() {
+                        SymbolFlags::FunctionExcludes
+                    } else {
+                        // `var x; function x() {}` is valid in non-strict mode, but `TypeScript`
+                        // doesn't care about non-strict mode, so we need to exclude this,
+                        // and further check in checker.
+                        SymbolFlags::FunctionExcludes - SymbolFlags::FunctionScopedVariable
+                    },
                 );
                 ident.symbol_id.set(Some(symbol_id));
             }

crates/oxc_syntax/src/symbol.rs

@@ -143,7 +143,7 @@ bitflags! {
         /// Block-scoped declarations are not allowed to be re-declared
         /// they can not merge with anything in the value space
         const BlockScopedVariableExcludes = Self::Value.bits();
-
+        const FunctionExcludes = Self::Value.bits() & !(Self::Function.bits() | Self::ValueModule.bits() | Self::Class.bits());
         const ClassExcludes = (Self::Value.bits() | Self::TypeAlias.bits()) & !(Self::ValueModule.bits() | Self::Interface.bits());
         const ImportBindingExcludes = Self::Import.bits() | Self::TypeImport.bits();
         // Type specific excludes

tasks/coverage/snapshots/parser_babel.snap

@@ -273,18 +273,6 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2022
   × Identifier `x` has already been declared
    ╭─[babel/packages/babel-parser/test/fixtures/es2022/class-static-block/duplicate-function-var-name/input.js:3:11]
  2 │     static {
- 3 │       var x;
-   ·           ┬
-   ·           ╰── `x` has already been declared here
- 4 │       function x() {}
-   ·                ┬
-   ·                ╰── It can not be redeclared here
- 5 │     }
-   ╰────
-
-  × Identifier `x` has already been declared
-   ╭─[babel/packages/babel-parser/test/fixtures/es2022/class-static-block/duplicate-function-var-name/input.js:3:11]
- 2 │     static {
  3 │       var x;
    ·           ┬
    ·           ╰── `x` has already been declared here
@@ -1345,16 +1333,6 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ·           ╰── It can not be redeclared here
    ╰────
 
-  × Identifier `foo` has already been declared
-   ╭─[babel/packages/babel-parser/test/fixtures/core/scope/dupl-bind-class-func/input.js:1:7]
- 1 │ class foo {};
-   ·       ─┬─
-   ·        ╰── `foo` has already been declared here
- 2 │ function foo () {};
-   ·          ─┬─
-   ·           ╰── It can not be redeclared here
-   ╰────
-
   × Identifier `foo` has already been declared
    ╭─[babel/packages/babel-parser/test/fixtures/core/scope/dupl-bind-class-let/input.js:1:7]
  1 │ class foo {};
@@ -1391,24 +1369,6 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ·            ╰── `f` has already been declared here
    ╰────
 
-  × Identifier `f` has already been declared
-   ╭─[babel/packages/babel-parser/test/fixtures/core/scope/dupl-bind-func-gen/input.js:1:12]
- 1 │ { function f() {} function* f() {} }
-   ·            ┬                ┬
-   ·            │                ╰── It can not be redeclared here
-   ·            ╰── `f` has already been declared here
-   ╰────
-
-  × Identifier `foo` has already been declared
-   ╭─[babel/packages/babel-parser/test/fixtures/core/scope/dupl-bind-func-module/input.js:1:10]
- 1 │ function foo() {}
-   ·          ─┬─
-   ·           ╰── `foo` has already been declared here
- 2 │ function foo() {}
-   ·          ─┬─
-   ·           ╰── It can not be redeclared here
-   ╰────
-
   × Identifier `foo` has already been declared
    ╭─[babel/packages/babel-parser/test/fixtures/core/scope/dupl-bind-func-module/input.js:1:10]
  1 │ function foo() {}
@@ -1427,14 +1387,6 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ·             ╰── `foo` has already been declared here
    ╰────
 
-  × Identifier `foo` has already been declared
-   ╭─[babel/packages/babel-parser/test/fixtures/core/scope/dupl-bind-func-module-sloppy/input.js:1:12]
- 1 │ { function foo() {} function foo() {} }
-   ·            ─┬─               ─┬─
-   ·             │                 ╰── It can not be redeclared here
-   ·             ╰── `foo` has already been declared here
-   ╰────
-
   × Identifier `foo` has already been declared
    ╭─[babel/packages/babel-parser/test/fixtures/core/scope/dupl-bind-func-var-sloppy/input.js:2:12]
  1 │ {