[destructuring] Implement parameter pattern matching.

src/scopes.cc

Index: src/scopes.cc
diff --git a/src/scopes.cc b/src/scopes.cc
index 63ae7ec1099627c187043ac2cb62e6e4d270f131..9b640d3eb9b654741e185b02284ad22afb4922d2 100644
--- a/src/scopes.cc
+++ b/src/scopes.cc
@@ -459,8 +459,9 @@ Variable* Scope::Lookup(const AstRawString* name) {
 }
 
 
-Variable* Scope::DeclareParameter(const AstRawString* name, VariableMode mode,
-                                  bool is_rest, bool* is_duplicate) {
+Variable* Scope::DeclareParameter(const AstRawString* name, Expression* pattern,
+                                  VariableMode mode, bool is_rest,
+                                  bool* is_duplicate) {
   DCHECK(!already_resolved());
   DCHECK(is_function_scope());
   Variable* var = variables_.Declare(this, name, mode, Variable::NORMAL,
@@ -470,9 +471,12 @@ Variable* Scope::DeclareParameter(const AstRawString* name, VariableMode mode,
     rest_parameter_ = var;
     rest_index_ = num_parameters();
   }
-  // TODO(wingo): Avoid O(n^2) check.
-  *is_duplicate = IsDeclaredParameter(name);
-  params_.Add(var, zone());
+
+  if (pattern == nullptr) {
+    // TODO(wingo): Avoid O(n^2) check.
+    *is_duplicate = IsDeclaredParameter(name);
+  }
+  params_.Add(Parameter(var, pattern), zone());
   return var;
 }
 
@@ -898,7 +902,7 @@ void Scope::Print(int n) {
     PrintF(" (");
     for (int i = 0; i < params_.length(); i++) {
       if (i > 0) PrintF(", ");
-      PrintName(params_[i]->raw_name());
+      PrintName(params_[i].var->raw_name());
     }
     PrintF(")");
   }
@@ -1337,7 +1341,7 @@ bool Scope::MustAllocateInContext(Variable* var) {
 
 bool Scope::HasArgumentsParameter(Isolate* isolate) {
   for (int i = 0; i < params_.length(); i++) {
-    if (params_[i]->name().is_identical_to(
+    if (params_[i].var->name().is_identical_to(
             isolate->factory()->arguments_string())) {
       return true;
     }
@@ -1398,7 +1402,7 @@ void Scope::AllocateParameterLocals(Isolate* isolate) {
   // receive the highest parameter index for that parameter; thus iteration
   // order is relevant!
   for (int i = params_.length() - 1; i >= 0; --i) {
-    Variable* var = params_[i];
+    Variable* var = params_[i].var;
     if (var == rest_parameter_) continue;
 
     DCHECK(var->scope() == this);