fix accesses to this in arrow functions

Change-Id: I4c0cfc3a120fc0b246760886b576e92d3f7623ff
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

4 files changed, 33 insertions, 7 deletions

diff --git a/src/qml/compiler/qv4codegen.cpp b/src/qml/compiler/qv4codegen.cpp
index 786753ab80..d61f79f0fc 100644
--- a/src/qml/compiler/qv4codegen.cpp
+++ b/src/qml/compiler/qv4codegen.cpp
@@ -2717,6 +2717,12 @@ bool Codegen::visit(ThisExpression *)
     if (hasError)
         return false;
 
+    if (_context->isArrowFunction) {
+        Reference r = referenceForName(QStringLiteral("this"), false);
+        r.isReadonly = true;
+        _expr.setResult(r);
+        return false;
+    }
     _expr.setResult(Reference::fromThis(this));
     return false;
 }
diff --git a/src/qml/compiler/qv4compilercontext.cpp b/src/qml/compiler/qv4compilercontext.cpp
index 4ee6d2c179..1b4c084ab4 100644
--- a/src/qml/compiler/qv4compilercontext.cpp
+++ b/src/qml/compiler/qv4compilercontext.cpp
@@ -241,6 +241,13 @@ void Context::emitBlockHeader(Codegen *codegen)
         Instruction::ConvertThisToObject convert;
         bytecodeGenerator->addInstruction(convert);
     }
+    if (innerFunctionAccessesThis) {
+        Instruction::LoadReg load;
+        load.reg = CallData::This;
+        bytecodeGenerator->addInstruction(load);
+        Codegen::Reference r = codegen->referenceForName(QStringLiteral("this"), true);
+        r.storeConsumeAccumulator();
+    }
 
     if (contextType == ContextType::Global || (contextType == ContextType::Eval && !isStrict)) {
         // variables in global code are properties of the global context object, not locals as with other functions.
diff --git a/src/qml/compiler/qv4compilercontext_p.h b/src/qml/compiler/qv4compilercontext_p.h
index 3df0aa6b3a..8713b0a188 100644
--- a/src/qml/compiler/qv4compilercontext_p.h
+++ b/src/qml/compiler/qv4compilercontext_p.h
@@ -201,6 +201,7 @@ struct Context {
     bool isArrowFunction = false;
     bool isGenerator = false;
     bool usesThis = false;
+    bool innerFunctionAccessesThis = false;
     bool hasTry = false;
     bool returnsClosure = false;
     mutable bool argumentsCanEscape = false;
diff --git a/src/qml/compiler/qv4compilerscanfunctions.cpp b/src/qml/compiler/qv4compilerscanfunctions.cpp
index e0a745ebb1..dafb1c360d 100644
--- a/src/qml/compiler/qv4compilerscanfunctions.cpp
+++ b/src/qml/compiler/qv4compilerscanfunctions.cpp
@@ -742,6 +742,8 @@ void ScanFunctions::calcEscapingVariables()
                 }
                 Q_ASSERT(c);
                 c->hasDirectEval = true;
+                if (!c->isStrict)
+                    c->innerFunctionAccessesThis = true;
             }
             Context *c = inner;
             while (c) {
@@ -751,17 +753,26 @@ void ScanFunctions::calcEscapingVariables()
         }
         if (inner->usesThis) {
             inner->usesThis = false;
-            if (!inner->isStrict) {
-                Context *c = inner;
-                while (c->contextType == ContextType::Block) {
-                    c = c->parent;
-                }
-                Q_ASSERT(c);
-                c->usesThis = true;
+            bool innerFunctionAccessesThis = false;
+            Context *c = inner;
+            while (c->contextType == ContextType::Block || c->isArrowFunction) {
+                innerFunctionAccessesThis |= c->isArrowFunction;
+                c = c->parent;
             }
+            Q_ASSERT(c);
+            if (!inner->isStrict)
+                c->usesThis = true;
+            c->innerFunctionAccessesThis |= innerFunctionAccessesThis;
         }
     }
     for (Context *c : qAsConst(m->contextMap)) {
+        if (c->innerFunctionAccessesThis) {
+            // add an escaping 'this' variable
+            c->addLocalVar(QStringLiteral("this"), Context::VariableDefinition, VariableScope::Let);
+            c->requiresExecutionContext = true;
+            auto m = c->members.find(QStringLiteral("this"));
+            m->canEscape = true;
+        }
         if (c->allVarsEscape && c->contextType == ContextType::Block && c->members.isEmpty())
             c->allVarsEscape = false;
         if (c->contextType == ContextType::Global || (!c->isStrict && c->contextType == ContextType::Eval) || m->debugMode)
@@ -801,6 +812,7 @@ void ScanFunctions::calcEscapingVariables()
         qDebug() << "==== escaping variables ====";
         for (Context *c : qAsConst(m->contextMap)) {
             qDebug() << "Context" << c << c->name << "requiresExecutionContext" << c->requiresExecutionContext << "isStrict" << c->isStrict;
+            qDebug() << "    isArrowFunction" << c->isArrowFunction << "innerFunctionAccessesThis" << c->innerFunctionAccessesThis;
             qDebug() << "    parent:" << c->parent;
             if (c->argumentsCanEscape)
                 qDebug() << "    Arguments escape";