fix(transformer/typescript) shadowed imports have not been removed (#4550)

close: #4423

Author: Dunqing

crates/oxc_transformer/src/typescript/annotations.rs

@@ -4,6 +4,7 @@ use std::{cell::Cell, rc::Rc};
 
 use oxc_allocator::Vec as ArenaVec;
 use oxc_ast::ast::*;
+use oxc_semantic::SymbolFlags;
 use oxc_span::{Atom, GetSpan, Span, SPAN};
 use oxc_syntax::{
     operator::AssignmentOperator, reference::ReferenceFlag, scope::ScopeFlags, symbol::SymbolId,
@@ -496,6 +497,15 @@ impl<'a> TypeScriptAnnotations<'a> {
 
     pub fn has_value_reference(&self, name: &str, ctx: &TraverseCtx<'a>) -> bool {
         if let Some(symbol_id) = ctx.scopes().get_root_binding(name) {
+            // `import T from 'mod'; const T = 1;` The T has a value redeclaration
+            // `import T from 'mod'; type T = number;` The T has a type redeclaration
+            // If the symbol is still a value symbol after SymbolFlags::Import is removed, then it's a value redeclaration.
+            // That means the import is shadowed, and we can safely remove the import.
+            let has_value_redeclaration =
+                (ctx.symbols().get_flag(symbol_id) - SymbolFlags::Import).is_value();
+            if has_value_redeclaration {
+                return false;
+            }
             if ctx
                 .symbols()
                 .get_resolved_references(symbol_id)

tasks/transform_conformance/oxc.snap.md

@@ -1,12 +1,12 @@
 commit: 12619ffe
 
-Passed: 4/7
+Passed: 5/8
 
 # All Passed:
 * babel-plugin-transform-react-jsx
 
 
-# babel-plugin-transform-typescript (3/6)
+# babel-plugin-transform-typescript (4/7)
 * computed-constant-value/input.ts
 * enum-member-reference/input.ts
 * export-elimination/input.ts

tasks/transform_conformance/tests/babel-plugin-transform-typescript/test/fixtures/redeclarations/input.ts

@@ -0,0 +1,15 @@
+// CASE 1: redeclaration of VariableDeclaration
+import { A } from './a';
+const A: A = 0;
+export {A};
+
+// CASE 2: redeclaration of TypeAlias
+import { T } from "./t";
+type T = number;
+export { T }
+
+// CASE 3: redeclaration of VariableDeclaration and TypeAlias
+import { B } from './b';
+const B: B = 0;
+type B = number;
+export { B }

tasks/transform_conformance/tests/babel-plugin-transform-typescript/test/fixtures/redeclarations/output.js

@@ -0,0 +1,12 @@
+// CASE 1: redeclaration of VariableDeclaration
+const A = 0;
+export { A };
+
+// CASE 2: redeclaration of TypeAlias
+import { T } from "./t";
+export { T };
+
+// CASE 3: redeclaration of VariableDeclaration and TypeAlias
+const B = 0;
+export { B };
+