[destructuring] Implement basic binding destructuring infrastructure

src/pattern-matcher.cc

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/ast.h"
+#include "src/parser.h"
+
+namespace v8 {
+

[arv (Not doing code reviews), 2015/05/08 19:09:49]

Can I has .h file?

+namespace internal {
+
+
+bool Parser::PatternMatcher::IsSingleVariableBinding() const {
+  return pattern_->IsVariableProxy();
+}
+
+
+const AstRawString* Parser::PatternMatcher::SingleName() const {
+  DCHECK(IsSingleVariableBinding());
+  return pattern_->AsVariableProxy()->raw_name();
+}
+
+
+void Parser::PatternMatcher::DeclareAndInitializeVariables(Expression* value,
+                                                           bool* ok) {
+  ok_ = ok;
+  RecurseIntoSubpattern(pattern_, value);
+}
+
+
+void Parser::PatternMatcher::VisitVariableProxy(VariableProxy* pattern) {
+  Expression* value = current_value_;
+  decl_->scope->RemoveUnresolved(pattern->AsVariableProxy());
+
+  // Declare variable.
+  // Note that we *always* must treat the initial value via a separate init
+  // assignment for variables and constants because the value must be assigned
+  // when the variable is encountered in the source. But the variable/constant
+  // is declared (and set to 'undefined') upon entering the function within
+  // which the variable or constant is declared. Only function variables have
+  // an initial value in the declaration (because they are initialized upon
+  // entering the function).
+  //
+  // If we have a const declaration, in an inner scope, the proxy is always
+  // bound to the declared variable (independent of possibly surrounding with
+  // statements).
+  // For let/const declarations in harmony mode, we can also immediately
+  // pre-resolve the proxy because it resides in the same scope as the
+  // declaration.
+  Parser* parser = decl_->parser;
+  const AstRawString* name = pattern->raw_name();
+  VariableProxy* proxy = parser->NewUnresolved(name, decl_->mode);
+  Declaration* declaration = factory()->NewVariableDeclaration(
+      proxy, decl_->mode, decl_->scope, decl_->pos);
+  Variable* var = parser->Declare(declaration, decl_->mode != VAR, ok_);
+  if (!*ok_) return;
+  DCHECK_NOT_NULL(var);
+  DCHECK(!proxy->is_resolved() || proxy->var() == var);
+  var->set_initializer_position(decl_->initializer_position);
+  (*decl_->nvars)++;
+  if (decl_->declaration_scope->num_var_or_const() > kMaxNumFunctionLocals) {
+    parser->ReportMessage("too_many_variables");
+    *ok_ = false;
+    return;
+  }
+  if (decl_->names) {
+    decl_->names->Add(name, zone());
+  }
+
+
+  // Global variable declarations must be compiled in a specific
+  // way. When the script containing the global variable declaration
+  // is entered, the global variable must be declared, so that if it
+  // doesn't exist (on the global object itself, see ES5 errata) it
+  // gets created with an initial undefined value. This is handled
+  // by the declarations part of the function representing the
+  // top-level global code; see Runtime::DeclareGlobalVariable. If
+  // it already exists (in the object or in a prototype), it is
+  // *not* touched until the variable declaration statement is
+  // executed.
+  //
+  // Executing the variable declaration statement will always
+  // guarantee to give the global object an own property.
+  // This way, global variable declarations can shadow
+  // properties in the prototype chain, but only after the variable
+  // declaration statement has been executed. This is important in
+  // browsers where the global object (window) has lots of
+  // properties defined in prototype objects.
+  if (decl_->initialization_scope()->is_script_scope() &&
+      !IsLexicalVariableMode(decl_->mode)) {
+    // Compute the arguments for the runtime
+    // call.test-parsing/InitializedDeclarationsInStrictForOfError
+    ZoneList<Expression*>* arguments =
+        new (zone()) ZoneList<Expression*>(3, zone());
+    // We have at least 1 parameter.
+    arguments->Add(factory()->NewStringLiteral(name, decl_->pos), zone());
+    CallRuntime* initialize;
+
+    if (decl_->is_const) {
+      arguments->Add(value, zone());
+      value = NULL;  // zap the value to avoid the unnecessary assignment
+
+      // Construct the call to Runtime_InitializeConstGlobal
+      // and add it to the initialization statement block.
+      // Note that the function does different things depending on
+      // the number of arguments (1 or 2).
+      initialize = factory()->NewCallRuntime(
+          ast_value_factory()->initialize_const_global_string(),
+          Runtime::FunctionForId(Runtime::kInitializeConstGlobal), arguments,
+          decl_->pos);
+    } else {
+      // Add language mode.
+      // We may want to pass singleton to avoid Literal allocations.
+      LanguageMode language_mode =
+          decl_->initialization_scope()->language_mode();
+      arguments->Add(factory()->NewNumberLiteral(language_mode, decl_->pos),
+                     zone());
+
+      // Be careful not to assign a value to the global variable if
+      // we're in a with. The initialization value should not
+      // necessarily be stored in the global object in that case,
+      // which is why we need to generate a separate assignment node.
+      if (value != NULL && !decl_->inside_with()) {
+        arguments->Add(value, zone());
+        value = NULL;  // zap the value to avoid the unnecessary assignment
+        // Construct the call to Runtime_InitializeVarGlobal
+        // and add it to the initialization statement block.
+        initialize = factory()->NewCallRuntime(
+            ast_value_factory()->initialize_var_global_string(),
+            Runtime::FunctionForId(Runtime::kInitializeVarGlobal), arguments,
+            decl_->pos);
+      } else {
+        initialize = NULL;
+      }
+    }
+
+    if (initialize != NULL) {
+      decl_->block->AddStatement(
+          factory()->NewExpressionStatement(initialize, RelocInfo::kNoPosition),
+          zone());
+    }
+  } else if (decl_->needs_init) {
+    // Constant initializations always assign to the declared constant which
+    // is always at the function scope level. This is only relevant for
+    // dynamically looked-up variables and constants (the
+    // stest-parsing/InitializedDeclarationsInStrictForOfError tart context for

[arv (Not doing code reviews), 2015/05/08 19:09:49]

typo

[Dmitry Lomov (no reviews), 2015/05/11 11:07:28]

Done.

+    // constant lookups is always the function context, while it is the top
+    // context for var declared variables). Sigh...
+    // For 'let' and 'const' declared variables in harmony mode the
+    // initialization also always assigns to the declared variable.
+    DCHECK(proxy != NULL);

[arv (Not doing code reviews), 2015/05/08 19:09:49]

DCHECK_NOT_NULL

[Dmitry Lomov (no reviews), 2015/05/11 11:07:28]

Done.

+    DCHECK(proxy->var() != NULL);
+    DCHECK(value != NULL);
+    Assignment* assignment =
+        factory()->NewAssignment(decl_->init_op, proxy, value, decl_->pos);
+    decl_->block->AddStatement(
+        factory()->NewExpressionStatement(assignment, RelocInfo::kNoPosition),
+        zone());
+    value = NULL;
+  }
+
+  // Add an assignment node to the initialization statement block if we still
+  // have a pending initialization value.
+  if (value != NULL) {
+    DCHECK(decl_->mode == VAR);
+    // 'var' initializations are simply assignments (with all the consequences
+    // if they are inside a 'with' statement - they may change a 'with' object
+    // property).
+    VariableProxy* proxy =
+        decl_->initialization_scope()->NewUnresolved(factory(), name);
+    Assignment* assignment =
+        factory()->NewAssignment(decl_->init_op, proxy, value, decl_->pos);
+    decl_->block->AddStatement(
+        factory()->NewExpressionStatement(assignment, RelocInfo::kNoPosition),
+        zone());
+  }
+}
+
+
+void Parser::PatternMatcher::VisitObjectLiteral(ObjectLiteral* pattern) {
+  auto temp = decl_->declaration_scope->NewTemporary(
+      ast_value_factory()->empty_string());
+  auto assignment =
+      factory()->NewAssignment(Token::ASSIGN, factory()->NewVariableProxy(temp),
+                               current_value_, RelocInfo::kNoPosition);
+  decl_->block->AddStatement(
+      factory()->NewExpressionStatement(assignment, RelocInfo::kNoPosition),
+      zone());
+  auto properties = pattern->properties();
+  for (auto i = properties->begin(); i != properties->end(); i++) {

[arv (Not doing code reviews), 2015/05/08 19:09:49]

Can we do?

for (auto property : properties) {

[Dmitry Lomov (no reviews), 2015/05/11 11:07:28]

Done.

+    ObjectLiteralProperty* property = *i;
+
+    RecurseIntoSubpattern(
+        property->value(),
+        factory()->NewProperty(factory()->NewVariableProxy(temp),
+                               property->key(), RelocInfo::kNoPosition));

[arv (Not doing code reviews), 2015/05/08 19:09:49]

TODO(dslomov): Computed property names

[Dmitry Lomov (no reviews), 2015/05/11 11:07:28]

Done.

+  }
+}
+
+
+void Parser::PatternMatcher::VisitArrayLiteral(ArrayLiteral* node) {
+  // TODO(dslomov): implement.
+}
+
+
+// =============== UNREACHABLE =============================
+void Parser::PatternMatcher::VisitProperty(Property* node) { UNREACHABLE(); }

[arv (Not doing code reviews), 2015/05/08 19:09:49]

This is only unreachable in binding patterns:

var o = {x: 1};
({y: o.x} = {y: 2});
assert(o.x === 2);

[Dmitry Lomov (no reviews), 2015/05/11 11:07:28]

I am not dealing with assignment patterns yet. As the code is now, this is
unreachable.

+
+
+void Parser::PatternMatcher::Visit(AstNode* node) { UNREACHABLE(); }
+
+
+void Parser::PatternMatcher::VisitVariableDeclaration(
+    VariableDeclaration* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitExportDeclaration(ExportDeclaration* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitEmptyStatement(EmptyStatement* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitContinueStatement(ContinueStatement* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitBreakStatement(BreakStatement* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitDebuggerStatement(DebuggerStatement* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitNativeFunctionLiteral(
+    NativeFunctionLiteral* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitLiteral(Literal* node) { UNREACHABLE(); }
+
+
+void Parser::PatternMatcher::VisitRegExpLiteral(RegExpLiteral* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitThisFunction(ThisFunction* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitSuperReference(
+    v8::internal::SuperReference* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitImportDeclaration(ImportDeclaration* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitExpressionStatement(
+    ExpressionStatement* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitReturnStatement(ReturnStatement* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitYield(Yield* node) { UNREACHABLE(); }
+
+
+void Parser::PatternMatcher::VisitThrow(Throw* node) { UNREACHABLE(); }
+
+
+void Parser::PatternMatcher::VisitUnaryOperation(UnaryOperation* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitCountOperation(CountOperation* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitBlock(Block* node) { UNREACHABLE(); }
+
+
+void Parser::PatternMatcher::VisitFunctionDeclaration(
+    FunctionDeclaration* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitCallRuntime(CallRuntime* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitWithStatement(WithStatement* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitDoWhileStatement(DoWhileStatement* node) {

[arv (Not doing code reviews), 2015/05/08 19:09:49]

Maybe a macro for all of these?

[Dmitry Lomov (no reviews), 2015/05/11 11:07:28]

Done.

+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitWhileStatement(WhileStatement* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitTryCatchStatement(TryCatchStatement* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitTryFinallyStatement(
+    TryFinallyStatement* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitAssignment(Assignment* node) {

[arv (Not doing code reviews), 2015/05/08 19:09:49]

TODO(dslomov): Implement

var {x: y = 42} = {};
assert(y === 42);

[Dmitry Lomov (no reviews), 2015/05/11 11:07:28]

Done.

+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitBinaryOperation(BinaryOperation* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitCompareOperation(CompareOperation* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitSpread(Spread* node) { UNREACHABLE(); }

[arv (Not doing code reviews), 2015/05/08 19:09:48]

TODO(dslomov): Implement

var [...xs] = []

[Dmitry Lomov (no reviews), 2015/05/11 11:07:28]

Done.

+
+
+void Parser::PatternMatcher::VisitForInStatement(ForInStatement* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitForOfStatement(ForOfStatement* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitConditional(Conditional* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitIfStatement(IfStatement* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitSwitchStatement(SwitchStatement* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitCaseClause(CaseClause* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitForStatement(ForStatement* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitClassLiteral(ClassLiteral* node) {
+  UNREACHABLE();
+}
+
+
+void Parser::PatternMatcher::VisitCall(Call* node) { UNREACHABLE(); }
+
+
+void Parser::PatternMatcher::VisitCallNew(CallNew* node) { UNREACHABLE(); }
+
+
+void Parser::PatternMatcher::VisitFunctionLiteral(FunctionLiteral* node) {
+  UNREACHABLE();
+}
+}
+}  // namespace v8::internal