C++: fix code completion for decltyped type

example:
struct Foo { int bar; };
Foo foo() { return Foo; }
typedef decltype(foo()) TypedefedFooWithDecltype;
void fun()
{
  decltype(foo()) decltypeFoo;
  decltypeFoo.;// code completion should work here

  TypedefedFooWithDecltype typedefedFooWithDecltype;
  typedefedFooWithDecltype.;// code completion should work here
}

Started-by: Przemyslaw Gorszkowski <pgorszkowski@gmail.com>
Task-number: QTCREATORBUG-14483
Change-Id: I296ceed9d896c68cf0651265afb08a1fc42f9a68
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>

src/libs/3rdparty/cplusplus/Bind.cpp

@@ -1921,9 +1921,22 @@ bool Bind::visit(SimpleDeclarationAST *ast)
         methodKey = methodKeyForInvokableToken(tokenKind(ast->qt_invokable_token));
 
     // unsigned qt_invokable_token = ast->qt_invokable_token;
+    unsigned declTypeStartOfExpression = 0;
+    unsigned declTypeEndOfExpression = 0;
+    bool isTypedef = false;
     FullySpecifiedType type;
     for (SpecifierListAST *it = ast->decl_specifier_list; it; it = it->next) {
         type = this->specifier(it->value, type);
+        if (type.isTypedef())
+            isTypedef = true;
+
+        type.setTypedef(isTypedef);
+        if (type.isDecltype()) {
+            if (DecltypeSpecifierAST *decltypeSpec = it->value->asDecltypeSpecifier()) {
+                declTypeStartOfExpression = decltypeSpec->expression->firstToken();
+                declTypeEndOfExpression = decltypeSpec->expression->lastToken();
+            }
+        }
     }
 
     List<Symbol *> **symbolTail = &ast->symbols;
@@ -1982,6 +1995,9 @@ bool Bind::visit(SimpleDeclarationAST *ast)
                 unsigned endOfExpression = initializer->lastToken();
                 decl->setInitializer(asStringLiteral(startOfExpression, endOfExpression));
             }
+        } else if (declTy.isDecltype()) {
+            decl->setInitializer(asStringLiteral(declTypeStartOfExpression,
+                                                 declTypeEndOfExpression));
         }
 
         if (_scope->isClass()) {
@@ -3028,6 +3044,7 @@ bool Bind::visit(TypeofSpecifierAST *ast)
 bool Bind::visit(DecltypeSpecifierAST *ast)
 {
     _type = this->expression(ast->expression);
+    _type.setDecltype(true);
     return false;
 }
 

src/libs/3rdparty/cplusplus/FullySpecifiedType.cpp

@@ -100,6 +100,12 @@ bool FullySpecifiedType::isAuto() const
 void FullySpecifiedType::setAuto(bool isAuto)
 { f._isAuto = isAuto; }
 
+bool FullySpecifiedType::isDecltype() const
+{ return f._isDecltype; }
+
+void FullySpecifiedType::setDecltype(bool isDecltype)
+{ f._isDecltype = isDecltype; }
+
 bool FullySpecifiedType::isRegister() const
 { return f._isRegister; }
 

src/libs/3rdparty/cplusplus/FullySpecifiedType.h

@@ -58,6 +58,9 @@ public:
     bool isAuto() const;
     void setAuto(bool isAuto);
 
+    bool isDecltype() const;
+    void setDecltype(bool isDecltype);
+
     bool isRegister() const;
     void setRegister(bool isRegister);
 
@@ -125,6 +128,7 @@ private:
         // storage class specifiers
         unsigned _isFriend: 1;
         unsigned _isAuto: 1;
+        unsigned _isDecltype: 1;
         unsigned _isRegister: 1;
         unsigned _isStatic: 1;
         unsigned _isExtern: 1;

src/libs/cplusplus/LookupContext.h

@@ -41,6 +41,7 @@
 #include <cplusplus/Control.h>
 #include <cplusplus/Name.h>
 
+#include <QEnableSharedFromThis>
 #include <QSet>
 #include <QMap>
 
@@ -99,7 +100,9 @@ private:
     friend class CreateBindings;
 };
 
-class CPLUSPLUS_EXPORT CreateBindings: protected SymbolVisitor
+class CPLUSPLUS_EXPORT CreateBindings
+        : protected SymbolVisitor
+        , public QEnableSharedFromThis<CreateBindings>
 {
     Q_DISABLE_COPY(CreateBindings)
 
@@ -119,6 +122,9 @@ public:
     QSharedPointer<Control> control() const
     { return _control; }
 
+    Snapshot &snapshot()
+    { return _snapshot; }
+
     /// Adds an expression document in order to keep their symbols and names alive
     void addExpressionDocument(Document::Ptr document)
     { _expressionDocuments.append(document); }

src/libs/cplusplus/ResolveExpression.cpp

@@ -526,48 +526,6 @@ bool ResolveExpression::visit(QualifiedNameAST *ast)
     return false;
 }
 
-namespace {
-
-class DeduceAutoCheck : public ASTVisitor
-{
-public:
-    DeduceAutoCheck(const Identifier *id, TranslationUnit *tu)
-        : ASTVisitor(tu), _id(id), _block(false)
-    {
-        accept(tu->ast());
-    }
-
-    virtual bool preVisit(AST *)
-    {
-        if (_block)
-            return false;
-
-        return true;
-    }
-
-    virtual bool visit(SimpleNameAST *ast)
-    {
-        if (ast->name
-                && ast->name->identifier()
-                && strcmp(ast->name->identifier()->chars(), _id->chars()) == 0) {
-            _block = true;
-        }
-
-        return false;
-    }
-
-    virtual bool visit(MemberAccessAST *ast)
-    {
-        accept(ast->base_expression);
-        return false;
-    }
-
-    const Identifier *_id;
-    bool _block;
-};
-
-} // namespace anonymous
-
 bool ResolveExpression::visit(SimpleNameAST *ast)
 {
     QList<LookupItem> candidates = _context.lookup(ast->name, _scope);
@@ -581,7 +539,7 @@ bool ResolveExpression::visit(SimpleNameAST *ast)
         if (item.declaration() == 0)
             continue;
 
-        if (item.type().isAuto()) {
+        if (item.type().isAuto() || item.type().isDecltype()) {
             const Declaration *decl = item.declaration()->asDeclaration();
             if (!decl)
                 continue;
@@ -590,35 +548,10 @@ bool ResolveExpression::visit(SimpleNameAST *ast)
             if (_autoDeclarationsBeingResolved.contains(decl))
                 continue;
 
-            const StringLiteral *initializationString = decl->getInitializer();
+            newCandidates +=
-            if (initializationString == 0)
+                    TypeResolver::resolveDeclInitializer(*_context.bindings(), decl,
-                continue;
+                                                         _autoDeclarationsBeingResolved << decl,
-
+                                                         ast->name->identifier());
-            const QByteArray &initializer =
-                    QByteArray::fromRawData(initializationString->chars(),
-                                            initializationString->size()).trimmed();
-
-            // Skip lambda-function initializers
-            if (initializer.length() > 0 && initializer[0] == '[')
-                continue;
-
-            TypeOfExpression exprTyper;
-            exprTyper.setExpandTemplates(true);
-            Document::Ptr doc = _context.document(QString::fromLocal8Bit(decl->fileName()));
-            exprTyper.init(doc, _context.snapshot(), _context.bindings(),
-                           QSet<const Declaration* >(_autoDeclarationsBeingResolved) << decl);
-
-            Document::Ptr exprDoc =
-                    documentForExpression(exprTyper.preprocessedExpression(initializer));
-            exprDoc->check();
-            _context.bindings()->addExpressionDocument(exprDoc);
-
-            DeduceAutoCheck deduceAuto(ast->name->identifier(), exprDoc->translationUnit());
-            if (deduceAuto._block)
-                continue;
-
-            newCandidates += exprTyper(extractExpressionAST(exprDoc), exprDoc,
-                                       decl->enclosingScope());
         } else {
             item.setType(item.declaration()->type());
             item.setScope(item.declaration()->enclosingScope());

src/libs/cplusplus/TypeResolver.cpp

@@ -30,6 +30,7 @@
 
 #include "TypeResolver.h"
 #include "Overview.h"
+#include "TypeOfExpression.h"
 
 #include <QDebug>
 
@@ -37,6 +38,48 @@ static const bool debug = ! qgetenv("QTC_LOOKUPCONTEXT_DEBUG").isEmpty();
 
 namespace CPlusPlus {
 
+namespace {
+
+class DeduceAutoCheck : public ASTVisitor
+{
+public:
+    DeduceAutoCheck(const Identifier *id, TranslationUnit *tu)
+        : ASTVisitor(tu), _id(id), _block(false)
+    {
+        accept(tu->ast());
+    }
+
+    virtual bool preVisit(AST *)
+    {
+        if (_block)
+            return false;
+
+        return true;
+    }
+
+    virtual bool visit(SimpleNameAST *ast)
+    {
+        if (ast->name
+                && ast->name->identifier()
+                && strcmp(ast->name->identifier()->chars(), _id->chars()) == 0) {
+            _block = true;
+        }
+
+        return false;
+    }
+
+    virtual bool visit(MemberAccessAST *ast)
+    {
+        accept(ast->base_expression);
+        return false;
+    }
+
+    const Identifier *_id;
+    bool _block;
+};
+
+} // namespace anonymous
+
 void TypeResolver::resolve(FullySpecifiedType *type, Scope **scope, LookupScope *binding)
 {
     QSet<Symbol *> visited;
@@ -115,6 +158,43 @@ QList<LookupItem> TypeResolver::typedefsFromScopeUpToFunctionScope(const Name *n
     return results;
 }
 
+// Resolves auto and decltype initializer string
+QList<LookupItem> TypeResolver::resolveDeclInitializer(
+        CreateBindings &factory, const Declaration *decl,
+        const QSet<const Declaration* > &declarationsBeingResolved,
+        const Identifier *id)
+{
+    const StringLiteral *initializationString = decl->getInitializer();
+    if (initializationString == 0)
+        return QList<LookupItem>();
+
+    const QByteArray &initializer =
+            QByteArray::fromRawData(initializationString->chars(),
+                                    initializationString->size()).trimmed();
+
+    // Skip lambda-function initializers
+    if (initializer.length() > 0 && initializer[0] == '[')
+        return QList<LookupItem>();
+
+    TypeOfExpression exprTyper;
+    exprTyper.setExpandTemplates(true);
+    Document::Ptr doc = factory.snapshot().document(QString::fromLocal8Bit(decl->fileName()));
+    exprTyper.init(doc, factory.snapshot(), factory.sharedFromThis(), declarationsBeingResolved);
+
+    Document::Ptr exprDoc =
+            documentForExpression(exprTyper.preprocessedExpression(initializer));
+    factory.addExpressionDocument(exprDoc);
+    exprDoc->check();
+
+    if (id) {
+        DeduceAutoCheck deduceAuto(id, exprDoc->translationUnit());
+        if (deduceAuto._block)
+            return QList<LookupItem>();
+    }
+
+    return exprTyper(extractExpressionAST(exprDoc), exprDoc, decl->enclosingScope());
+}
+
 bool TypeResolver::isTypedefWithName(const Declaration *declaration, const Name *name)
 {
     if (declaration->isTypedef()) {
@@ -130,7 +210,7 @@ bool TypeResolver::findTypedef(const QList<LookupItem> &namedTypeItems, FullySpe
 {
     foreach (const LookupItem &it, namedTypeItems) {
         Symbol *declaration = it.declaration();
-        if (!declaration || !declaration->isTypedef())
+        if (!declaration || (!declaration->isTypedef() && !declaration->type().isDecltype()))
             continue;
         if (visited.contains(declaration))
             break;
@@ -145,6 +225,17 @@ bool TypeResolver::findTypedef(const QList<LookupItem> &namedTypeItems, FullySpe
                         _factory.control()->referenceType(
                             declaration->type(),
                             declaration->type()->asReferenceType()->isRvalueReference()));
+        } else if (declaration->type().isDecltype()) {
+            Declaration *decl = declaration->asDeclaration();
+            const QList<LookupItem> resolved =
+                    resolveDeclInitializer(_factory, decl, QSet<const Declaration* >() << decl);
+            if (!resolved.isEmpty()) {
+                LookupItem item = resolved.first();
+                *type = item.type();
+                *scope = item.scope();
+                _binding = item.binding();
+                return true;
+            }
         } else {
             *type = declaration->type();
         }

src/libs/cplusplus/TypeResolver.h

@@ -40,6 +40,10 @@ class TypeResolver
 public:
     TypeResolver(CreateBindings &factory) : _factory(factory) {}
     void resolve(FullySpecifiedType *type, Scope **scope, LookupScope *binding);
+    static QList<LookupItem> resolveDeclInitializer(
+            CreateBindings &factory, const Declaration *decl,
+            const QSet<const Declaration *> &declarationsBeingResolved,
+            const Identifier *id = 0);
 
 private:
     NamedType *getNamedType(FullySpecifiedType& type) const;

src/plugins/cpptools/cppcompletion_test.cpp

@@ -2940,6 +2940,29 @@ void CppToolsPlugin::test_completion_data()
     ) << _("p.") << (QStringList()
         << QLatin1String("Nested2")
         << QLatin1String("bar"));
+
+    QTest::newRow("simple_decltype_declaration") << _(
+            "struct Foo { int bar; };\n"
+            "Foo foo;\n"
+            "void fun() {\n"
+            "   decltype(foo) s;\n"
+            "   @\n"
+            "}\n"
+    ) << _("s.") << (QStringList()
+            << QLatin1String("Foo")
+            << QLatin1String("bar"));
+
+    QTest::newRow("typedefed_decltype_declaration") << _(
+            "struct Foo { int bar; };\n"
+            "Foo foo;\n"
+            "typedef decltype(foo) TypedefedFooWithDecltype;\n"
+            "void fun() {\n"
+            "   TypedefedFooWithDecltype s;\n"
+            "   @\n"
+            "}\n"
+    ) << _("s.") << (QStringList()
+            << QLatin1String("Foo")
+            << QLatin1String("bar"));
 }
 
 void CppToolsPlugin::test_completion_member_access_operator()