qmlcompiler: Implement function type

Implements a very limited function type we mainly use for linting
purposes right  now. This allows us to know when some binding or function
returns another function.

Limitations:
- We do not distinguish between generators and regular functions
- We do not record any parameter information or types
- We do not record any return types
- There is no code generation for actually utilizing these closures

Change-Id: Ic43218d9a1a3a3966d5afbd42943192e5a61c864
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

src/qmlcompiler/qqmljscodegenerator.cpp

@@ -493,7 +493,7 @@ void QQmlJSCodeGenerator::generate_MoveRegExp(int regExpId, int destReg)
 void QQmlJSCodeGenerator::generate_LoadClosure(int value)
 {
     Q_UNUSED(value)
-    BYTECODE_UNIMPLEMENTED();
+    reject(u"LoadClosure"_s);
 }
 
 void QQmlJSCodeGenerator::generate_LoadName(int nameIndex)

src/qmlcompiler/qqmljstypepropagator.cpp

@@ -258,7 +258,9 @@ void QQmlJSTypePropagator::generate_MoveRegExp(int regExpId, int destReg)
 void QQmlJSTypePropagator::generate_LoadClosure(int value)
 {
     Q_UNUSED(value)
-    INSTR_PROLOGUE_NOT_IMPLEMENTED();
+    // TODO: Check the function at index and see whether it's a generator to return another type
+    // instead.
+    setAccumulator(m_typeResolver->globalType(m_typeResolver->functionType()));
 }
 
 void QQmlJSTypePropagator::generate_LoadName(int nameIndex)

src/qmlcompiler/qqmljstyperesolver.cpp

@@ -87,6 +87,11 @@ QQmlJSTypeResolver::QQmlJSTypeResolver(QQmlJSImporter *importer)
     metaObjectType->setAccessSemantics(QQmlJSScope::AccessSemantics::Reference);
     m_metaObjectType = metaObjectType;
 
+    QQmlJSScope::Ptr functionType = QQmlJSScope::create();
+    functionType->setInternalName(u"function"_s);
+    functionType->setAccessSemantics(QQmlJSScope::AccessSemantics::Value);
+    m_functionType = functionType;
+
     m_jsGlobalObject = importer->jsGlobalObject();
     auto numberMethods = m_jsGlobalObject->methods(u"Number"_s);
     Q_ASSERT(numberMethods.length() == 1);

src/qmlcompiler/qqmljstyperesolver_p.h

@@ -80,6 +80,7 @@ public:
     QQmlJSScope::ConstPtr jsPrimitiveType() const { return m_jsPrimitiveType; }
     QQmlJSScope::ConstPtr listPropertyType() const { return m_listPropertyType; }
     QQmlJSScope::ConstPtr metaObjectType() const { return m_metaObjectType; }
+    QQmlJSScope::ConstPtr functionType() const { return m_functionType; }
     QQmlJSScope::ConstPtr jsGlobalObject() const { return m_jsGlobalObject; }
 
     QQmlJSScope::ConstPtr scopeForLocation(const QV4::CompiledData::Location &location) const;
@@ -208,6 +209,7 @@ protected:
     QQmlJSScope::ConstPtr m_jsPrimitiveType;
     QQmlJSScope::ConstPtr m_listPropertyType;
     QQmlJSScope::ConstPtr m_metaObjectType;
+    QQmlJSScope::ConstPtr m_functionType;
     QQmlJSScope::ConstPtr m_jsGlobalObject;
 
     QQmlJSScopesById m_objectsById;