Add support for destructuring variable declarations

Change-Id: Ia7f894fb61cfa760e253963ab4815d98103cfd9b
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

3 files changed, 44 insertions, 34 deletions

diff --git a/src/qml/compiler/qv4codegen.cpp b/src/qml/compiler/qv4codegen.cpp
index 0323012686..151e98c673 100644
--- a/src/qml/compiler/qv4codegen.cpp
+++ b/src/qml/compiler/qv4codegen.cpp
@@ -380,14 +380,7 @@ void Codegen::variableDeclaration(PatternElement *ast)
 
     if (!ast->initializer)
         return;
-    Reference rhs = expression(ast->initializer);
-    if (hasError)
-        return;
-
-    Reference lhs = referenceForName(ast->bindingIdentifier, true);
-    //### if lhs is a temp, this won't generate a temp-to-temp move. Same for when rhs is a const
-    rhs.loadInAccumulator();
-    lhs.storeConsumeAccumulator();
+    initializeAndDestructureBindingElement(ast, Reference());
 }
 
 void Codegen::variableDeclarationList(VariableDeclarationList *ast)
@@ -401,19 +394,25 @@ void Codegen::initializeAndDestructureBindingElement(AST::PatternElement *e, con
 {
     RegisterScope scope(this);
     Reference varToStore = e->bindingIdentifier.isNull() ? Reference::fromStackSlot(this, bytecodeGenerator->newRegister()) : referenceForName(e->bindingIdentifier, true);
-    if (e->initializer && baseRef == varToStore) {
-        baseRef.loadInAccumulator();
-        BytecodeGenerator::Jump jump = bytecodeGenerator->jumpNotUndefined();
-        expression(e->initializer).loadInAccumulator();
-        varToStore.storeConsumeAccumulator();
-        jump.link();
-    } else if (e->initializer) {
-        baseRef.loadInAccumulator();
-        BytecodeGenerator::Jump jump = bytecodeGenerator->jumpNotUndefined();
-        expression(e->initializer).loadInAccumulator();
-        jump.link();
-        varToStore.storeConsumeAccumulator();
-    } else if (baseRef != varToStore) {
+    if (e->initializer) {
+        if (!baseRef.isValid()) {
+            // assignment
+            expression(e->initializer).loadInAccumulator();
+            varToStore.storeConsumeAccumulator();
+        } else if (baseRef == varToStore) {
+            baseRef.loadInAccumulator();
+            BytecodeGenerator::Jump jump = bytecodeGenerator->jumpNotUndefined();
+            expression(e->initializer).loadInAccumulator();
+            varToStore.storeConsumeAccumulator();
+            jump.link();
+        } else {
+            baseRef.loadInAccumulator();
+            BytecodeGenerator::Jump jump = bytecodeGenerator->jumpNotUndefined();
+            expression(e->initializer).loadInAccumulator();
+            jump.link();
+            varToStore.storeConsumeAccumulator();
+        }
+    } else if (baseRef != varToStore && baseRef.isValid()) {
         baseRef.loadInAccumulator();
         varToStore.storeConsumeAccumulator();
     }
diff --git a/src/qml/compiler/qv4compilerscanfunctions.cpp b/src/qml/compiler/qv4compilerscanfunctions.cpp
index 3f98d7fd67..c6e792fc45 100644
--- a/src/qml/compiler/qv4compilerscanfunctions.cpp
+++ b/src/qml/compiler/qv4compilerscanfunctions.cpp
@@ -196,18 +196,30 @@ bool ScanFunctions::visit(PatternElement *ast)
     if (!ast->isVariableDeclaration())
         return true;
 
-    if (_context->isStrict && (ast->bindingIdentifier == QLatin1String("eval") || ast->bindingIdentifier == QLatin1String("arguments")))
-        _cg->throwSyntaxError(ast->identifierToken, QStringLiteral("Variable name may not be eval or arguments in strict mode"));
-    checkName(QStringRef(&ast->bindingIdentifier), ast->identifierToken);
-    if (ast->bindingIdentifier == QLatin1String("arguments"))
-        _context->usesArgumentsObject = Context::ArgumentsObjectNotUsed;
-    if (ast->scope == VariableScope::Const && !ast->initializer) {
-        _cg->throwSyntaxError(ast->identifierToken, QStringLiteral("Missing initializer in const declaration"));
-        return false;
-    }
-    if (!_context->addLocalVar(ast->bindingIdentifier, ast->initializer ? Context::VariableDefinition : Context::VariableDeclaration, ast->scope)) {
-        _cg->throwSyntaxError(ast->identifierToken, QStringLiteral("Identifier %1 has already been declared").arg(ast->bindingIdentifier));
-        return false;
+    QStringList names;
+    ast->boundNames(&names);
+
+    for (const QString &name : qAsConst(names)) {
+        if (_context->isStrict && (name == QLatin1String("eval") || name == QLatin1String("arguments")))
+            _cg->throwSyntaxError(ast->identifierToken, QStringLiteral("Variable name may not be eval or arguments in strict mode"));
+        checkName(QStringRef(&name), ast->identifierToken);
+        if (name == QLatin1String("arguments"))
+            _context->usesArgumentsObject = Context::ArgumentsObjectNotUsed;
+        if (ast->scope == VariableScope::Const && !ast->initializer) {
+            _cg->throwSyntaxError(ast->identifierToken, QStringLiteral("Missing initializer in const declaration"));
+            return false;
+        }
+        const Context::Member *m = nullptr;
+        if (_context->memberInfo(name, &m)) {
+            if (m->isLexicallyScoped() || ast->isLexicallyScoped()) {
+                _cg->throwSyntaxError(ast->identifierToken, QStringLiteral("Identifier %1 has already been declared").arg(name));
+                return false;
+            }
+        }
+        if (!_context->addLocalVar(name, ast->initializer ? Context::VariableDefinition : Context::VariableDeclaration, ast->scope)) {
+            _cg->throwSyntaxError(ast->identifierToken, QStringLiteral("Identifier %1 has already been declared").arg(ast->bindingIdentifier));
+            return false;
+        }
     }
     return true;
 }
diff --git a/src/qml/parser/qqmljs.g b/src/qml/parser/qqmljs.g
index 5200779924..bf733dd6cd 100644
--- a/src/qml/parser/qqmljs.g
+++ b/src/qml/parser/qqmljs.g
@@ -2824,7 +2824,6 @@ VariableDeclaration: BindingPattern Initializer;
 VariableDeclaration_In: BindingPattern Initializer_In;
 /.
     case $rule_number: {
-    UNIMPLEMENTED;
         auto *node = new (pool) AST::PatternElement(sym(1).Pattern, sym(2).Expression);
         node->identifierToken = loc(1);
         sym(1).Node = node;