Don't optimize global lookups if fast QML lookups are disabled

If fast QML lookups are disabled, we generally want to look up by
string. If the name then happens to be a member of the global JavaScript
object, we still don't want to directly access that, as the name could
have been overridden in a deeper context.

Fixes: QTBUG-73750
Change-Id: Id16110969123d91501064ba46bfad4c2a39e4650
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

3 files changed, 5 insertions, 2 deletions

diff --git a/src/qml/compiler/qqmlirbuilder_p.h b/src/qml/compiler/qqmlirbuilder_p.h
index 3dde929cc4..1a3ca4163e 100644
--- a/src/qml/compiler/qqmlirbuilder_p.h
+++ b/src/qml/compiler/qqmlirbuilder_p.h
@@ -622,6 +622,7 @@ struct Q_QML_PRIVATE_EXPORT JSCodeGen : public QV4::Compiler::Codegen
 
 protected:
     void beginFunctionBodyHook() override;
+    bool canAccelerateGlobalLookups() const override { return !_disableAcceleratedLookups; }
     Reference fallbackNameLookup(const QString &name) override;
 
 private:
diff --git a/src/qml/compiler/qv4codegen.cpp b/src/qml/compiler/qv4codegen.cpp
index fb3c66b123..04da41430c 100644
--- a/src/qml/compiler/qv4codegen.cpp
+++ b/src/qml/compiler/qv4codegen.cpp
@@ -2404,7 +2404,7 @@ Codegen::Reference Codegen::referenceForName(const QString &name, bool isLhs, co
 
     Reference r = Reference::fromName(this, name);
     r.global = useFastLookups && (resolved.type == Context::ResolvedName::Global);
-    if (!r.global && m_globalNames.contains(name))
+    if (!r.global && canAccelerateGlobalLookups() && m_globalNames.contains(name))
         r.global = true;
     return r;
 }
diff --git a/src/qml/compiler/qv4codegen_p.h b/src/qml/compiler/qv4codegen_p.h
index 3f96afc7c2..4d7001fe64 100644
--- a/src/qml/compiler/qv4codegen_p.h
+++ b/src/qml/compiler/qv4codegen_p.h
@@ -561,8 +561,10 @@ protected:
 
     Reference referenceForPropertyName(const Codegen::Reference &object, AST::PropertyName *name);
 
-    // Hook provided to implement QML lookup semantics
+    // Hooks provided to implement QML lookup semantics
+    virtual bool canAccelerateGlobalLookups() const { return true; }
     virtual Reference fallbackNameLookup(const QString &name);
+
     virtual void beginFunctionBodyHook() {}
 
     void emitReturn(const Reference &expr);