fix(hir): #5910 — var x = init in catch(x) assigns to catch param, not hoisted var

crates/perry-hir/src/destructuring/var_decl.rs

@@ -136,7 +136,24 @@ pub(crate) fn lower_var_decl_with_destructuring(
                     ctx.async_generator_func_names.insert(name.clone());
                 }
             }
-            let id = if let Some(pid) = pre_id {
+            // Annex B B.3.4: a `var <name> = init` whose name shadows a live
+            // `catch (<name>)` parameter assigns to the catch binding, so the
+            // function-scoped hoisted `var` keeps its pre-catch value. Target the
+            // catch parameter (innermost `lookup_local`) instead of reusing the
+            // hoisted id. Only a simple `var x = init` (a plain ident declarator
+            // with an initializer); a bare `var x;` re-declaration is inert and a
+            // destructuring pattern never names the catch param directly.
+            let shadows_catch_param = is_var_decl
+                && init.is_some()
+                && matches!(&decl.name, ast::Pat::Ident(_))
+                && ctx
+                    .catch_param_scopes
+                    .iter()
+                    .any(|scope| scope.contains(&name));
+            let id = if shadows_catch_param {
+                ctx.lookup_local(&name)
+                    .unwrap_or_else(|| ctx.define_local(name.clone(), ty.clone()))
+            } else if let Some(pid) = pre_id {
                 pid
             } else if ctx.scope_depth == 0
                 && ctx.inside_block_scope == 0

crates/perry-hir/src/lower/context.rs

@@ -114,6 +114,7 @@ impl LoweringContext {
             unresolved_ident_as_global: false,
             with_env_stack: Vec::new(),
             var_hoisted_ids: HashSet::new(),
+            catch_param_scopes: Vec::new(),
             annexb_block_fn_var_ids: HashMap::new(),
             annexb_block_fn_names_all: HashSet::new(),
             lexical_forward_decls: HashMap::new(),

crates/perry-hir/src/lower/lowering_context.rs

@@ -374,6 +374,15 @@ pub struct LoweringContext {
     /// continue to lexically shadow the object environment.
     pub(crate) with_env_stack: Vec<WithEnvFrame>,
     pub(crate) var_hoisted_ids: HashSet<LocalId>,
+    /// Names bound by an enclosing `catch (e)` parameter that is currently in
+    /// scope (a stack, innermost last). Annex B B.3.4: a `var e = init;` whose
+    /// name collides with a live catch parameter assigns to that *catch
+    /// parameter* binding, not the function-scoped hoisted `var` — so the outer
+    /// `var e` keeps its pre-catch value (test262 `annexB/language/statements/
+    /// try/catch-redeclared-var-statement`). `lower_var_decl_with_destructuring`
+    /// consults this to target the shadowing catch binding via `lookup_local`
+    /// instead of reusing the hoisted id. Pushed/popped around the catch body.
+    pub(crate) catch_param_scopes: Vec<HashSet<String>>,
     /// Annex B B.3.3 (#5297): for the function/program scope currently being
     /// lowered, maps each name declared by a *block-nested* `function f(){}`
     /// (legacy sloppy-mode block-level function declaration) to the enclosing-

crates/perry-hir/src/lower/stmt.rs

@@ -1570,7 +1570,22 @@ pub(crate) fn lower_stmt(
                     None
                 };
 
+                // Annex B B.3.4: track the (simple-ident) catch parameter name so
+                // a `var <name> = init` inside the catch body targets the catch
+                // binding, not the function-scoped hoisted `var`.
+                let mut pushed_catch_scope = false;
+                if let Some((_, ref pname)) = param {
+                    if matches!(catch_clause.param, Some(ast::Pat::Ident(_))) {
+                        let mut set = std::collections::HashSet::new();
+                        set.insert(pname.clone());
+                        ctx.catch_param_scopes.push(set);
+                        pushed_catch_scope = true;
+                    }
+                }
                 let mut catch_body = lower_block_stmt(ctx, &catch_clause.body)?;
+                if pushed_catch_scope {
+                    ctx.catch_param_scopes.pop();
+                }
                 for (i, stmt) in binding_stmts.into_iter().enumerate() {
                     catch_body.insert(i, stmt);
                 }