LibJS: Improve function hoisting across blocks

The parser now keeps track of a scope chain so that it can hoist
function declarations to the closest function scope.

1 files changed, 17 insertions, 1 deletions

diff --git a/Userland/Libraries/LibJS/Parser.h b/Userland/Libraries/LibJS/Parser.h
index a53352c940..0e231a3dff 100644
--- a/Userland/Libraries/LibJS/Parser.h
+++ b/Userland/Libraries/LibJS/Parser.h
@@ -196,13 +196,29 @@ private:
 
     [[nodiscard]] RulePosition push_start() { return { *this, position() }; }
 
+    struct Scope : public RefCounted<Scope> {
+        enum Type {
+            Function,
+            Block,
+        };
+
+        Type type;
+        RefPtr<Scope> parent;
+
+        NonnullRefPtrVector<FunctionDeclaration> function_declarations;
+        NonnullRefPtrVector<FunctionDeclaration> hoisted_function_declarations;
+
+        explicit Scope(Type, RefPtr<Scope>);
+        RefPtr<Scope> get_current_function_scope();
+    };
+
     struct ParserState {
         Lexer lexer;
         Token current_token;
         Vector<Error> errors;
         Vector<NonnullRefPtrVector<VariableDeclaration>> var_scopes;
         Vector<NonnullRefPtrVector<VariableDeclaration>> let_scopes;
-        Vector<NonnullRefPtrVector<FunctionDeclaration>> function_scopes;
+        RefPtr<Scope> current_scope;
 
         Vector<Vector<FunctionNode::Parameter>&> function_parameters;