CPlusPlus: Categorize "Find Usages" results

That is, find out whether a certain access was a read, a write, a
declaration or something else, and report the result to upper layers.
Follow-up patches can make this information visible to users.

Task-number: QTCREATORBUG-12734
Task-number: QTCREATORBUG-19373
Change-Id: Iee79e39dd1eb5a986a7e27846991e0e01b2c3a2f
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

4 files changed, 568 insertions, 15 deletions

diff --git a/src/libs/cplusplus/FindUsages.cpp b/src/libs/cplusplus/FindUsages.cpp
index 8b976d9532..8f7a66801f 100644
--- a/src/libs/cplusplus/FindUsages.cpp
+++ b/src/libs/cplusplus/FindUsages.cpp
@@ -28,16 +28,21 @@
 #include "Overview.h"
 
 #include <cplusplus/AST.h>
-#include <cplusplus/TranslationUnit.h>
+#include <cplusplus/ASTPath.h>
 #include <cplusplus/Control.h>
-#include <cplusplus/Names.h>
-#include <cplusplus/Symbols.h>
 #include <cplusplus/CoreTypes.h>
 #include <cplusplus/Literals.h>
+#include <cplusplus/Names.h>
 #include <cplusplus/Scope.h>
+#include <cplusplus/Symbols.h>
+#include <cplusplus/TranslationUnit.h>
+#include <cplusplus/TypeOfExpression.h>
+
+#include <utils/optional.h>
 
 #include <QDebug>
 
+
 using namespace CPlusPlus;
 
 FindUsages::FindUsages(const QByteArray &originalSource, Document::Ptr doc, const Snapshot &snapshot)
@@ -132,17 +137,251 @@ void FindUsages::reportResult(unsigned tokenIndex, const QList<LookupItem> &cand
         lineText = fetchLine(line);
     else
         lineText = matchingLine(tk);
-
-    if (col)
-        --col;  // adjust the column position.
-
     const int len = tk.utf16chars();
 
-    const Usage u(Utils::FilePath::fromString(_doc->fileName()), lineText, line, col, len);
+    const Usage u(Utils::FilePath::fromString(_doc->fileName()), lineText,
+                  getType(line, col, tokenIndex), line, col - 1, len);
     _usages.append(u);
     _references.append(tokenIndex);
 }
 
+Usage::Type FindUsages::getType(int line, int column, int tokenIndex)
+{
+    const auto containsToken = [tokenIndex](const AST *ast) {
+        return ast->firstToken() <= tokenIndex && ast->lastToken() > tokenIndex;
+    };
+    const auto isAssignment = [this](int token) {
+        switch (tokenKind(token)) {
+        case T_AMPER_EQUAL: case T_CARET_EQUAL: case T_SLASH_EQUAL: case T_EQUAL:
+        case T_MINUS_EQUAL: case T_PERCENT_EQUAL: case T_PIPE_EQUAL: case T_PLUS_EQUAL:
+        case T_STAR_EQUAL: case T_TILDE_EQUAL:
+            return true;
+        default:
+            return false;
+        }
+    };
+
+    // This is called for the type of the LHS of an (initialization) assignment.
+    // We consider the RHS to be writable through the LHS if the LHS is a pointer
+    // that is non-const at any element level, or if it is a a non-const reference.
+    static const auto getUsageTypeFromDataType = [](FullySpecifiedType type) {
+        if (type.isAuto())
+            return Usage::Type::Other;
+        if (const auto refType = type->asReferenceType())
+            return refType->elementType().isConst() ? Usage::Type::Read : Usage::Type::WritableRef;
+        while (type->isPointerType()) {
+            type = type->asPointerType()->elementType();
+            if (!type.isConst())
+                return Usage::Type::WritableRef;
+        }
+        return Usage::Type::Read;
+    };
+
+    const QList<AST *> astPath = ASTPath(_doc)(line, column);
+
+    // If we found a potential write access inside a lambda, we have to check whether the variable
+    // was captured by value. If so, it's not really a write access.
+    // FIXME: The parser does not record whether the capture was by reference.
+    const auto checkPotentialWrite = [&](Usage::Type usageType, auto startIt) {
+        if (usageType != Usage::Type::Write && usageType != Usage::Type::WritableRef)
+            return usageType;
+        for (auto it = startIt; it != astPath.rend(); ++it) {
+            if ((*it)->firstToken() > tokenIndex)
+                break;
+            const auto lambdaExpr = (*it)->asLambdaExpression();
+            if (!lambdaExpr)
+                continue;
+             LambdaCaptureAST * const captureAst = lambdaExpr->lambda_introducer->lambda_capture;
+             if (!captureAst)
+                 continue;
+             for (CaptureListAST *capList = captureAst->capture_list; capList;
+                  capList = capList->next) {
+                 if (!capList->value || !capList->value->identifier)
+                     continue;
+                 if (!Matcher::match(_declSymbol->name(), capList->value->identifier->name))
+                     continue;
+                 return capList->value->amper_token ? usageType : Usage::Type::Read;
+             }
+        }
+        return usageType;
+    };
+
+    const auto getTypeOfExpr = [&](ExpressionAST *expr, auto scopeSearchPos)
+            -> Utils::optional<LookupItem> {
+        if (!expr)
+            return {};
+        Scope *scope = nullptr;
+        for (auto it = scopeSearchPos; !scope && it != astPath.rend(); ++it) {
+            if (const auto stmt = (*it)->asCompoundStatement())
+                scope = stmt->symbol;
+            else if (const auto klass = (*it)->asClassSpecifier())
+                scope = klass->symbol;
+            else if (const auto ns = (*it)->asNamespace())
+                scope = ns->symbol;
+        }
+        if (!scope)
+            scope = _doc->globalNamespace();
+        const QList<LookupItem> items = typeofExpression(expr, _doc, scope);
+        if (items.isEmpty())
+            return {};
+        return Utils::optional<LookupItem>(items.first());
+    };
+
+    const auto getUsageTypeFromLhsAndRhs
+            = [&](const FullySpecifiedType &lhsType, ExpressionAST *rhs, auto scopeSearchPos) {
+        const Usage::Type usageType = getUsageTypeFromDataType(lhsType);
+        if (usageType != Usage::Type::Other)
+            return usageType;
+
+        // If the lhs has type auto, we use the RHS type.
+        const Utils::optional<LookupItem> item = getTypeOfExpr(rhs, scopeSearchPos);
+        if (!item)
+            return Usage::Type::Other;
+        return getUsageTypeFromDataType(item->type());
+    };
+
+    const auto getUsageTypeForCall = [&](auto callIt) {
+        CallAST * const call = (*callIt)->asCall();
+
+        // Check whether this is a member function call on the symbol we are looking for
+        // (possibly indirectly via a data member).
+        // If it is and the function is not const, then this is a potential write.
+        if (call->base_expression == *(callIt - 1)) {
+            for (auto it = callIt; it != astPath.rbegin(); --it) {
+                const auto memberAccess = (*it)->asMemberAccess();
+                if (!memberAccess)
+                    continue;
+                if (memberAccess->member_name == *(it - 1))
+                    return Usage::Type::Other;
+                const Utils::optional<LookupItem> item
+                        = getTypeOfExpr(memberAccess->base_expression, it);
+                if (!item)
+                    return Usage::Type::Other;
+                FullySpecifiedType baseExprType = item->type();
+                if (const auto refType = baseExprType->asReferenceType())
+                    baseExprType = refType->elementType();
+                while (const auto ptrType = baseExprType->asPointerType())
+                    baseExprType = ptrType->elementType();
+                Class *klass = baseExprType->asClassType();
+                const LookupContext context(_doc, _snapshot);
+                QList<LookupItem> items;
+                if (!klass) {
+                    if (const auto namedType = baseExprType->asNamedType()) {
+                        items = context.lookup(namedType->name(), item->scope());
+                        if (items.isEmpty())
+                            return Usage::Type::Other;
+                        klass = items.first().type()->asClassType();
+                    }
+                }
+                if (!klass)
+                    return Usage::Type::Other;
+                items = context.lookup(memberAccess->member_name->name, klass);
+                if (items.isEmpty())
+                    return Usage::Type::Other;
+                for (const LookupItem &item : qAsConst(items)) {
+                    if (item.type()->isFunctionType())
+                        return item.type().isConst() ? Usage::Type::Read : Usage::Type::WritableRef;
+                }
+            }
+            return Usage::Type::Other;
+        }
+
+        // Check whether our symbol is passed as an argument to the function.
+        // If it is and the corresponding parameter is a non-const pointer or reference,
+        // then this is a potential write.
+        bool match = false;
+        int argPos = -1;
+        for (ExpressionListAST *argList = call->expression_list; argList && !match;
+             argList = argList->next, ++argPos) {
+            match = argList->value == *(callIt - 1);
+        }
+        if (!match)
+            return Usage::Type::Other;
+        const Utils::optional<LookupItem> item = getTypeOfExpr(call->base_expression, callIt + 1);
+        if (!item)
+            return Usage::Type::Other;
+        Function * const func = item->type()->asFunctionType();
+        if (!func || func->argumentCount() <= argPos)
+            return Usage::Type::Other;
+        return getUsageTypeFromLhsAndRhs(func->argumentAt(argPos)->type(),
+                                         (*(callIt - 1))->asExpression(), callIt);
+    };
+
+    if (astPath.size() < 2 || !astPath.last()->asSimpleName())
+        return Usage::Type::Other;
+
+    for (auto it = astPath.rbegin() + 1; it != astPath.rend(); ++it) {
+        if ((*it)->asExpressionStatement())
+            return Usage::Type::Read;
+        if ((*it)->asLambdaCapture() || (*it)->asNamedTypeSpecifier()
+                || (*it)->asElaboratedTypeSpecifier()) {
+            return Usage::Type::Other;
+        }
+        if ((*it)->asTypenameTypeParameter())
+            return Usage::Type::Declaration;
+        if (ClassSpecifierAST *classSpec = (*it)->asClassSpecifier()) {
+            if (classSpec->name == *(it - 1))
+                return Usage::Type::Declaration;
+            continue;
+        }
+        if ((*it)->asCall())
+            return checkPotentialWrite(getUsageTypeForCall(it), it + 1);
+        if (const auto binExpr = (*it)->asBinaryExpression()) {
+            if (binExpr->left_expression == *(it - 1) && isAssignment(binExpr->binary_op_token))
+                return checkPotentialWrite(Usage::Type::Write, it + 1);
+            const Utils::optional<LookupItem> item = getTypeOfExpr(binExpr->left_expression, it + 1);
+            if (!item)
+                return Usage::Type::Other;
+            return checkPotentialWrite(getUsageTypeFromLhsAndRhs(
+                                           item->type(), binExpr->right_expression, it), it + 1);
+        }
+        if (const auto unaryOp = (*it)->asUnaryExpression()) {
+            switch (tokenKind(unaryOp->unary_op_token)) {
+            case T_PLUS_PLUS: case T_MINUS_MINUS:
+                return checkPotentialWrite(Usage::Type::Write, it + 1);
+            case T_AMPER: case T_STAR:
+                continue;
+            default:
+                return Usage::Type::Read;
+            }
+        }
+        if (const auto declaratorId = (*it)->asDeclaratorId()) {
+            // We don't want to classify constructors and destructors as declarations
+            // when listing class usages.
+            if (_declSymbol->asClass())
+                return Usage::Type::Other;
+            continue;
+        }
+        if (const auto declarator = (*it)->asDeclarator()) {
+            if (containsToken(declarator->core_declarator))
+                return Usage::Type::Declaration;
+            if (const auto decl = (*(it + 1))->asSimpleDeclaration()) {
+                if (decl->symbols && decl->symbols->value) {
+                    return checkPotentialWrite(
+                                getUsageTypeFromLhsAndRhs(decl->symbols->value->type(),
+                                                          declarator->initializer, it + 1), it + 1);
+                }
+            }
+            return Usage::Type::Other;
+        }
+        if (const auto retStmt = (*it)->asReturnStatement()) {
+            for (auto funcIt = it + 1; funcIt != astPath.rend(); ++funcIt) {
+                if (FunctionDefinitionAST * const funcAst = (*funcIt)->asFunctionDefinition()) {
+                    if (funcAst->symbol) {
+                        return checkPotentialWrite(
+                                    getUsageTypeFromLhsAndRhs(funcAst->symbol->type(),
+                                                              retStmt->expression, funcIt),
+                                    funcIt + 1);
+                    }
+                }
+            }
+            return Usage::Type::Other;
+        }
+    }
+
+    return Usage::Type::Other;
+}
+
 QString FindUsages::matchingLine(const Token &tk) const
 {
     const char *beg = _source.constData();
diff --git a/src/libs/cplusplus/FindUsages.h b/src/libs/cplusplus/FindUsages.h
index e0b37b12a8..a0e1130c15 100644
--- a/src/libs/cplusplus/FindUsages.h
+++ b/src/libs/cplusplus/FindUsages.h
@@ -39,13 +39,15 @@ namespace CPlusPlus {
 class CPLUSPLUS_EXPORT Usage
 {
 public:
+    enum class Type { Declaration, Read, Write, WritableRef, Other };
+
     Usage() = default;
-    Usage(const Utils::FilePath &path, const QString &lineText, int line, int col, int len)
-        : path(path), lineText(lineText), line(line), col(col), len(len) {}
+    Usage(const Utils::FilePath &path, const QString &lineText, Type t, int line, int col, int len)
+        : path(path), lineText(lineText), type(t), line(line), col(col), len(len) {}
 
-public:
     Utils::FilePath path;
     QString lineText;
+    Type type = Type::Other;
     int line = 0;
     int col = 0;
     int len = 0;
@@ -71,6 +73,7 @@ protected:
 
     void reportResult(unsigned tokenIndex, const Name *name, Scope *scope = nullptr);
     void reportResult(unsigned tokenIndex, const QList<LookupItem> &candidates);
+    Usage::Type getType(int line, int column, int tokenIndex);
 
     bool checkCandidates(const QList<LookupItem> &candidates) const;
     void checkExpression(unsigned startToken, unsigned endToken, Scope *scope = nullptr);
diff --git a/src/plugins/cpptools/cppfindreferences.cpp b/src/plugins/cpptools/cppfindreferences.cpp
index 131d0fca94..1f567bed7e 100644
--- a/src/plugins/cpptools/cppfindreferences.cpp
+++ b/src/plugins/cpptools/cppfindreferences.cpp
@@ -650,8 +650,9 @@ restart_search:
                 if (macro.name() == useMacro.name()) {
                     unsigned column;
                     const QString &lineSource = matchingLine(use.bytesBegin(), source, &column);
-                    usages.append(CPlusPlus::Usage(fileName, lineSource, use.beginLine(), column,
-                                        useMacro.nameToQString().size()));
+                    usages.append(CPlusPlus::Usage(fileName, lineSource,
+                                                   CPlusPlus::Usage::Type::Other, use.beginLine(),
+                                                   column, useMacro.nameToQString().size()));
                 }
             }
         }
diff --git a/tests/auto/cplusplus/findusages/tst_findusages.cpp b/tests/auto/cplusplus/findusages/tst_findusages.cpp
index 2dd9566021..3a88bf2a2e 100644
--- a/tests/auto/cplusplus/findusages/tst_findusages.cpp
+++ b/tests/auto/cplusplus/findusages/tst_findusages.cpp
@@ -133,6 +133,7 @@ private Q_SLOTS:
     void variableTemplateInExpression();
 
     void variadicMacros();
+    void writableRefs();
 };
 
 void tst_FindUsages::dump(const QList<Usage> &usages) const
@@ -181,6 +182,8 @@ void tst_FindUsages::inlineMethod()
     FindUsages findUsages(src, doc, snapshot);
     findUsages(arg);
     QCOMPARE(findUsages.usages().size(), 2);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Read);
     QCOMPARE(findUsages.references().size(), 2);
 }
 
@@ -214,6 +217,9 @@ void tst_FindUsages::lambdaCaptureByValue()
     FindUsages findUsages(src, doc, snapshot);
     findUsages(d);
     QCOMPARE(findUsages.usages().size(), 3);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(2).type, Usage::Type::Read);
 }
 
 void tst_FindUsages::lambdaCaptureByReference()
@@ -246,6 +252,10 @@ void tst_FindUsages::lambdaCaptureByReference()
     FindUsages findUsages(src, doc, snapshot);
     findUsages(d);
     QCOMPARE(findUsages.usages().size(), 3);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Other);
+    QEXPECT_FAIL(nullptr, "parser does not record capture type", Continue);
+    QCOMPARE(findUsages.usages().at(2).type, Usage::Type::Write);
 }
 
 void tst_FindUsages::shadowedNames_1()
@@ -276,6 +286,8 @@ void tst_FindUsages::shadowedNames_1()
     FindUsages findUsages(src, doc, snapshot);
     findUsages(d);
     QCOMPARE(findUsages.usages().size(), 2);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Other);
 }
 
 void tst_FindUsages::shadowedNames_2()
@@ -309,6 +321,9 @@ void tst_FindUsages::shadowedNames_2()
     FindUsages findUsages(src, doc, snapshot);
     findUsages(d);
     QCOMPARE(findUsages.usages().size(), 3);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(2).type, Usage::Type::Other);
 }
 
 void tst_FindUsages::staticVariables()
@@ -355,6 +370,11 @@ void tst_FindUsages::staticVariables()
     FindUsages findUsages(src, doc, snapshot);
     findUsages(d);
     QCOMPARE(findUsages.usages().size(), 5);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(2).type, Usage::Type::Write);
+    QCOMPARE(findUsages.usages().at(3).type, Usage::Type::Write);
+    QCOMPARE(findUsages.usages().at(4).type, Usage::Type::Write);
 }
 
 void tst_FindUsages::functionNameFoundInArguments()
@@ -387,12 +407,15 @@ void foo2(int b=bar()){}    // 3rd result
 
     QCOMPARE(find.usages().size(), 3);
 
+    QCOMPARE(find.usages()[0].type, Usage::Type::Declaration);
     QCOMPARE(find.usages()[0].line, 1);
     QCOMPARE(find.usages()[0].col, 5);
 
+    QCOMPARE(find.usages()[1].type, Usage::Type::Other);
     QCOMPARE(find.usages()[1].line, 4);
     QCOMPARE(find.usages()[1].col, 16);
 
+    QCOMPARE(find.usages()[2].type, Usage::Type::Other);
     QCOMPARE(find.usages()[2].line, 5);
     QCOMPARE(find.usages()[2].col, 16);
 }
@@ -451,18 +474,22 @@ struct Struct{
     find(memberFunctionFoo);
     QCOMPARE(find.usages().size(), 2);
 
+    QCOMPARE(find.usages()[0].type, Usage::Type::Declaration);
     QCOMPARE(find.usages()[0].line, 3);
     QCOMPARE(find.usages()[0].col, 15);
 
+    QCOMPARE(find.usages()[1].type, Usage::Type::Other);
     QCOMPARE(find.usages()[1].line, 5);
     QCOMPARE(find.usages()[1].col, 24);
 
     find(variableFoo);
     QCOMPARE(find.usages().size(), 2);
 
+    QCOMPARE(find.usages()[0].type, Usage::Type::Declaration);
     QCOMPARE(find.usages()[0].line, 5);
     QCOMPARE(find.usages()[0].col, 12);
 
+    QCOMPARE(find.usages()[1].type, Usage::Type::Read);
     QCOMPARE(find.usages()[1].line, 6);
     QCOMPARE(find.usages()[1].col, 22);
 }
@@ -519,6 +546,13 @@ int main() {
     FindUsages find(src, doc, snapshot);
     find(sv);
     QCOMPARE(find.usages().size(), 7);
+    QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(find.usages().at(1).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(2).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(3).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(4).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(5).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(6).type, Usage::Type::Read);
 }
 
 void tst_FindUsages::templateConstructorVsCallOperator()
@@ -571,6 +605,13 @@ int main()
     FindUsages find(src, doc, snapshot);
     find(sv);
     QCOMPARE(find.usages().size(), 7);
+    QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(find.usages().at(1).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(2).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(3).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(4).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(5).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(6).type, Usage::Type::Read);
 }
 
 #if 0
@@ -667,6 +708,8 @@ void tst_FindUsages::qproperty_1()
     FindUsages findUsages(src, doc, snapshot);
     findUsages(setX_method);
     QCOMPARE(findUsages.usages().size(), 2);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Declaration);
     QCOMPARE(findUsages.references().size(), 2);
 }
 
@@ -711,6 +754,8 @@ void tst_FindUsages::instantiateTemplateWithNestedClass()
     FindUsages findUsages(src, doc, snapshot);
     findUsages(barDeclaration);
     QCOMPARE(findUsages.usages().size(), 2);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Read);
 }
 
 void tst_FindUsages::operatorAsteriskOfNestedClassOfTemplateClass_QTCREATORBUG9006()
@@ -756,6 +801,8 @@ void tst_FindUsages::operatorAsteriskOfNestedClassOfTemplateClass_QTCREATORBUG90
     findUsages(fooDeclaration);
 
     QCOMPARE(findUsages.usages().size(), 2);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Read);
 }
 
 void tst_FindUsages::anonymousClass_QTCREATORBUG8963()
@@ -799,6 +846,8 @@ void tst_FindUsages::anonymousClass_QTCREATORBUG8963()
     findUsages(isNotIntDeclaration);
 
     QCOMPARE(findUsages.usages().size(), 2);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Read);
 }
 
 void tst_FindUsages::anonymousClass_QTCREATORBUG11859()
@@ -839,9 +888,13 @@ void tst_FindUsages::anonymousClass_QTCREATORBUG11859()
     FindUsages findUsages(src, doc, snapshot);
     findUsages(fooAsStruct);
     QCOMPARE(findUsages.references().size(), 1);
+    QCOMPARE(findUsages.usages().size(), 1);
+    QCOMPARE(findUsages.usages().first().type, Usage::Type::Declaration);
 
     findUsages(fooAsMemberOfAnonymousStruct);
     QCOMPARE(findUsages.references().size(), 2);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Read);
 }
 
 void tst_FindUsages::using_insideGlobalNamespace()
@@ -882,6 +935,9 @@ void tst_FindUsages::using_insideGlobalNamespace()
     findUsages(structSymbol);
 
     QCOMPARE(findUsages.usages().size(), 3);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(2).type, Usage::Type::Other);
 }
 
 void tst_FindUsages::using_insideNamespace()
@@ -925,6 +981,9 @@ void tst_FindUsages::using_insideNamespace()
     findUsages(structSymbol);
 
     QCOMPARE(findUsages.usages().size(), 3);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(2).type, Usage::Type::Other);
 }
 
 void tst_FindUsages::using_insideFunction()
@@ -965,6 +1024,9 @@ void tst_FindUsages::using_insideFunction()
     findUsages(structSymbol);
 
     QCOMPARE(findUsages.usages().size(), 3);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(2).type, Usage::Type::Other);
 }
 
 void tst_FindUsages::operatorArrowOfNestedClassOfTemplateClass_QTCREATORBUG9005()
@@ -1009,6 +1071,8 @@ void tst_FindUsages::operatorArrowOfNestedClassOfTemplateClass_QTCREATORBUG9005(
     FindUsages findUsages(src, doc, snapshot);
     findUsages(fooDeclaration);
     QCOMPARE(findUsages.usages().size(), 2);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Read);
 }
 
 void tst_FindUsages::templateClassParameters()
@@ -1044,6 +1108,11 @@ void tst_FindUsages::templateClassParameters()
     FindUsages findUsages(src, doc, snapshot);
     findUsages(templArgument);
     QCOMPARE(findUsages.usages().size(), 5);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(2).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(3).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(4).type, Usage::Type::Other);
 }
 
 void tst_FindUsages::templateClass_className()
@@ -1085,6 +1154,13 @@ void tst_FindUsages::templateClass_className()
     FindUsages findUsages(src, doc, snapshot);
     findUsages(classTS);
     QCOMPARE(findUsages.usages().size(), 7);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(2).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(3).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(4).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(5).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(6).type, Usage::Type::Other);
 }
 
 void tst_FindUsages::templateFunctionParameters()
@@ -1118,6 +1194,10 @@ void tst_FindUsages::templateFunctionParameters()
     FindUsages findUsages(src, doc, snapshot);
     findUsages(templArgument);
     QCOMPARE(findUsages.usages().size(), 4);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(2).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(3).type, Usage::Type::Other);
 }
 
 void tst_FindUsages::templatedFunction_QTCREATORBUG9749()
@@ -1148,6 +1228,8 @@ void tst_FindUsages::templatedFunction_QTCREATORBUG9749()
     FindUsages findUsages(src, doc, snapshot);
     findUsages(func);
     QCOMPARE(findUsages.usages().size(), 2);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Other);
 }
 
 void tst_FindUsages::usingInDifferentNamespace_QTCREATORBUG7978()
@@ -1187,6 +1269,9 @@ void tst_FindUsages::usingInDifferentNamespace_QTCREATORBUG7978()
     FindUsages findUsages(src, doc, snapshot);
     findUsages(templateClass);
     QCOMPARE(findUsages.usages().size(), 3);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Other);
+    QCOMPARE(findUsages.usages().at(2).type, Usage::Type::Other);
 }
 
 void tst_FindUsages::unicodeIdentifier()
@@ -1214,6 +1299,8 @@ void tst_FindUsages::unicodeIdentifier()
     findUsages(declaration);
     const QList<Usage> usages = findUsages.usages();
     QCOMPARE(usages.size(), 2);
+    QCOMPARE(findUsages.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(findUsages.usages().at(1).type, Usage::Type::Write);
     QCOMPARE(usages.at(0).len, 7);
     QCOMPARE(usages.at(1).len, 7);
 }
@@ -1243,8 +1330,10 @@ void tst_FindUsages::inAlignas()
     FindUsages find(src, doc, snapshot);
     find(c);
     QCOMPARE(find.usages().size(), 2);
+    QCOMPARE(find.usages()[0].type, Usage::Type::Declaration);
     QCOMPARE(find.usages()[0].line, 1);
     QCOMPARE(find.usages()[0].col, 7);
+    QCOMPARE(find.usages()[1].type, Usage::Type::Other);
     QCOMPARE(find.usages()[1].line, 2);
     QCOMPARE(find.usages()[1].col, 15);
 }
@@ -1284,8 +1373,10 @@ void tst_FindUsages::memberAccessAsTemplate()
         FindUsages find(src, doc, snapshot);
         find(c);
         QCOMPARE(find.usages().size(), 2);
+        QCOMPARE(find.usages()[0].type, Usage::Type::Declaration);
         QCOMPARE(find.usages()[0].line, 1);
         QCOMPARE(find.usages()[0].col, 7);
+        QCOMPARE(find.usages()[1].type, Usage::Type::Other);
         QCOMPARE(find.usages()[1].line, 11);
         QCOMPARE(find.usages()[1].col, 24);
     }
@@ -1303,8 +1394,10 @@ void tst_FindUsages::memberAccessAsTemplate()
         FindUsages find(src, doc, snapshot);
         find(f);
         QCOMPARE(find.usages().size(), 2);
+        QCOMPARE(find.usages()[0].type, Usage::Type::Declaration);
         QCOMPARE(find.usages()[0].line, 4);
         QCOMPARE(find.usages()[0].col, 7);
+        QCOMPARE(find.usages()[1].type, Usage::Type::Other);
         QCOMPARE(find.usages()[1].line, 11);
         QCOMPARE(find.usages()[1].col, 11);
     }
@@ -1344,6 +1437,10 @@ void tst_FindUsages::variadicFunctionTemplate()
         FindUsages find(src, doc, snapshot);
         find(v);
         QCOMPARE(find.usages().size(), 4);
+        QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+        QCOMPARE(find.usages().at(1).type, Usage::Type::Read);
+        QCOMPARE(find.usages().at(2).type, Usage::Type::Read);
+        QCOMPARE(find.usages().at(3).type, Usage::Type::Read);
     }
 }
 
@@ -1391,8 +1488,13 @@ void tst_FindUsages::typeTemplateParameterWithDefault()
         FindUsages find(src, doc, snapshot);
         find(xv);
         QCOMPARE(find.usages().size(), 2);
+        QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+        QCOMPARE(find.usages().at(1).type, Usage::Type::Read);
         find(sv);
         QCOMPARE(find.usages().size(), 3);
+        QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+        QCOMPARE(find.usages().at(1).type, Usage::Type::Read);
+        QCOMPARE(find.usages().at(2).type, Usage::Type::Read);
     }
 }
 
@@ -1430,6 +1532,8 @@ void tst_FindUsages::resolveOrder_for_templateFunction_vs_function()
         FindUsages find(src, doc, snapshot);
         find(xv);
         QCOMPARE(find.usages().size(), 2);
+        QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+        QCOMPARE(find.usages().at(1).type, Usage::Type::Read);
     }
 }
 
@@ -1470,6 +1574,9 @@ void tst_FindUsages::templateArrowOperator_with_defaultType()
         FindUsages find(src, doc, snapshot);
         find(sv);
         QCOMPARE(find.usages().size(), 3);
+        QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+        QCOMPARE(find.usages().at(1).type, Usage::Type::Read);
+        QCOMPARE(find.usages().at(2).type, Usage::Type::Read);
     }
 }
 
@@ -1489,7 +1596,7 @@ void tst_FindUsages::templateSpecialization_with_IntArgument()
                            "    S<2> s2;\n"
                            "    s0.s.value;\n"
                            "    s1.s.value;\n"
-                           "    s2.s.value;\n"
+                           "    s2.s.value = s2.s.value;\n"
                            "}\n";
 
     Document::Ptr doc = Document::create("templateSpecialization_with_IntArgument");
@@ -1549,18 +1656,25 @@ void tst_FindUsages::templateSpecialization_with_IntArgument()
         find(sv[1]);
         QCOMPARE(find.usages().size(), 2);
 
+        QCOMPARE(find.usages()[0].type, Usage::Type::Declaration);
         QCOMPARE(find.usages()[0].line, 2);
         QCOMPARE(find.usages()[0].col, 15);
+        QCOMPARE(find.usages()[1].type, Usage::Type::Read);
         QCOMPARE(find.usages()[1].line, 13);
         QCOMPARE(find.usages()[1].col, 9);
 
         find(sv[2]);
-        QCOMPARE(find.usages().size(), 2);
+        QCOMPARE(find.usages().size(), 3);
 
+        QCOMPARE(find.usages()[0].type, Usage::Type::Declaration);
         QCOMPARE(find.usages()[0].line, 3);
         QCOMPARE(find.usages()[0].col, 15);
+        QCOMPARE(find.usages()[1].type, Usage::Type::Write);
         QCOMPARE(find.usages()[1].line, 14);
         QCOMPARE(find.usages()[1].col, 9);
+        QCOMPARE(find.usages()[2].type, Usage::Type::Read);
+        QCOMPARE(find.usages()[2].line, 14);
+        QCOMPARE(find.usages()[2].col, 22);
     }
 }
 
@@ -1621,16 +1735,20 @@ void tst_FindUsages::templateSpecialization_with_BoolArgument()
         find(sv[0]);
         QCOMPARE(find.usages().size(), 2);
 
+        QCOMPARE(find.usages()[0].type, Usage::Type::Declaration);
         QCOMPARE(find.usages()[0].line, 1);
         QCOMPARE(find.usages()[0].col, 15);
+        QCOMPARE(find.usages()[1].type, Usage::Type::Read);
         QCOMPARE(find.usages()[1].line, 9);
         QCOMPARE(find.usages()[1].col, 9);
 
         find(sv[1]);
         QCOMPARE(find.usages().size(), 2);
 
+        QCOMPARE(find.usages()[0].type, Usage::Type::Declaration);
         QCOMPARE(find.usages()[0].line, 2);
         QCOMPARE(find.usages()[0].col, 15);
+        QCOMPARE(find.usages()[1].type, Usage::Type::Read);
         QCOMPARE(find.usages()[1].line, 10);
         QCOMPARE(find.usages()[1].col, 9);
     }
@@ -1693,16 +1811,20 @@ void tst_FindUsages::templatePartialSpecialization()
         find(sv[0]);
         QCOMPARE(find.usages().size(), 2);
 
+        QCOMPARE(find.usages()[0].type, Usage::Type::Declaration);
         QCOMPARE(find.usages()[0].line, 1);
         QCOMPARE(find.usages()[0].col, 15);
+        QCOMPARE(find.usages()[1].type, Usage::Type::Read);
         QCOMPARE(find.usages()[1].line, 9);
         QCOMPARE(find.usages()[1].col, 10);
 
         find(sv[1]);
         QCOMPARE(find.usages().size(), 2);
 
+        QCOMPARE(find.usages()[0].type, Usage::Type::Declaration);
         QCOMPARE(find.usages()[0].line, 2);
         QCOMPARE(find.usages()[0].col, 15);
+        QCOMPARE(find.usages()[1].type, Usage::Type::Read);
         QCOMPARE(find.usages()[1].line, 10);
         QCOMPARE(find.usages()[1].col, 10);
     }
@@ -1758,12 +1880,18 @@ int main()
 
     find(sv[0]);
     QCOMPARE(find.usages().size(), 2);
+    QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(find.usages().at(1).type, Usage::Type::Read);
 
     find(sv[1]);
     QCOMPARE(find.usages().size(), 2);
+    QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(find.usages().at(1).type, Usage::Type::Read);
 
     find(sv[2]);
     QCOMPARE(find.usages().size(), 2);
+    QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(find.usages().at(1).type, Usage::Type::Read);
 }
 
 void tst_FindUsages::template_SFINAE_1()
@@ -1802,6 +1930,8 @@ int main(){
     FindUsages find(src, doc, snapshot);
     find(sv);
     QCOMPARE(find.usages().size(), 2);
+    QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(find.usages().at(1).type, Usage::Type::Read);
 }
 
 void tst_FindUsages::variableTemplateInExpression()
@@ -1845,6 +1975,8 @@ int main(){
     FindUsages find(src, doc, snapshot);
     find(sv);
     QCOMPARE(find.usages().size(), 2);
+    QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(find.usages().at(1).type, Usage::Type::Read);
 }
 
 void tst_FindUsages::variadicMacros()
@@ -1883,6 +2015,184 @@ int main(){}
     FindUsages find(src, doc, snapshot);
     find(sv);
     QCOMPARE(find.usages().size(), 2);
+    QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(find.usages().at(1).type, Usage::Type::Read);
+}
+
+void tst_FindUsages::writableRefs()
+{
+    const QByteArray src = R"(
+struct S {
+    static int value;
+    static void *p;
+    static const void *p2;
+    struct Nested {
+        int constFunc() const;
+        void nonConstFunc();
+    } n;
+    Nested constFunc() const;
+    void nonConstFunc();
+};
+void func1(int &);
+void func2(const int &);
+void func3(int *);
+void func4(const int *);
+void func5(int);
+int main()
+{
+    S s;
+    auto *p = &s.value;
+    int **pp;
+    p = &s.value;
+    *pp = &s.value;
+    //p = &s::value; FIXME: This one is not found at all...
+    s.p = &s.value;
+    // s::p = &s::value; FIXME: Same here.
+    (&s)->p = &((new S)->value);
+    const int *p2 = &s.value;
+    s.p2 = &s.value;
+    int * const p3 = &s.value;
+    int &r = s.value;
+    const int &cr = s.value;
+    func1(s.value);
+    func2(s.value);
+    func3(&s.value);
+    func4(&s.value);
+    func5(s.value);
+    *p = 5;
+    func1(*p);
+    func2(*p);
+    func3(p);
+    func4(p);
+    func5(p);
+    int &r2 = *p;
+    const int &cr2 = *p;
+    s = S();
+    auto * const ps = &s;
+    const auto *ps2 = &s;
+    auto &pr = s;
+    const auto pr2 = &s;
+    s.constFunc().nonConstFunc();
+    s.nonConstFunc();
+    (&s)->nonConstFunc();
+    s.n.constFunc();
+    s.n.nonConstFunc();
+}
+)";
+
+    const Document::Ptr doc = Document::create("writableRefs");
+    doc->setUtf8Source(src);
+    doc->check();
+
+    QVERIFY(doc->diagnosticMessages().isEmpty());
+    QCOMPARE(doc->globalSymbolCount(), 7);
+
+    Snapshot snapshot;
+    snapshot.insert(doc);
+
+    Class * const structS = doc->globalSymbolAt(0)->asClass();
+    QVERIFY(structS);
+    QCOMPARE(structS->name()->identifier()->chars(), "S");
+    QCOMPARE(structS->memberCount(), 7);
+
+    Declaration * const sv = structS->memberAt(0)->asDeclaration();
+    QVERIFY(sv);
+    QCOMPARE(sv->name()->identifier()->chars(), "value");
+
+    // Access to struct member
+    FindUsages find(src, doc, snapshot);
+    find(sv);
+    QCOMPARE(find.usages().size(), 16);
+    QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(find.usages().at(1).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(2).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(3).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(4).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(5).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(6).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(7).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(8).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(9).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(10).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(11).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(12).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(13).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(14).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(15).type, Usage::Type::Read);
+
+    Function * const main = doc->globalSymbolAt(6)->asFunction();
+    QVERIFY(main);
+    QCOMPARE(main->memberCount(), 1);
+    Block * const block = main->memberAt(0)->asBlock();
+    QVERIFY(block);
+    QCOMPARE(block->memberCount(), 13);
+
+    // Access to pointer
+    Declaration * const p = block->memberAt(1)->asDeclaration();
+    QVERIFY(p);
+    QCOMPARE(p->name()->identifier()->chars(), "p");
+    find(p);
+    QCOMPARE(find.usages().size(), 10);
+    QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(find.usages().at(1).type, Usage::Type::Write);
+    QCOMPARE(find.usages().at(2).type, Usage::Type::Write);
+    QCOMPARE(find.usages().at(3).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(4).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(5).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(6).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(7).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(8).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(9).type, Usage::Type::Read);
+
+    // Access to struct variable via its members
+    Declaration * const varS = block->memberAt(0)->asDeclaration();
+    QVERIFY(varS);
+    QCOMPARE(varS->name()->identifier()->chars(), "s");
+    find(varS);
+    QCOMPARE(find.usages().size(), 28);
+    QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(find.usages().at(1).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(2).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(3).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(4).type, Usage::Type::Write);
+    QCOMPARE(find.usages().at(5).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(6).type, Usage::Type::Write);
+    QCOMPARE(find.usages().at(7).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(8).type, Usage::Type::Write);
+    QCOMPARE(find.usages().at(9).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(10).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(11).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(12).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(13).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(14).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(15).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(16).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(17).type, Usage::Type::Read);
+
+    // Direct access to struct variable
+    QCOMPARE(find.usages().at(18).type, Usage::Type::Write);
+    QCOMPARE(find.usages().at(19).type, Usage::Type::WritableRef);
+    QEXPECT_FAIL(nullptr, "parser does not record const qualifier for auto types", Continue);
+    QCOMPARE(find.usages().at(20).type, Usage::Type::Read);
+    QEXPECT_FAIL(nullptr, "parser does not record reference qualifier for auto types", Continue);
+    QCOMPARE(find.usages().at(21).type, Usage::Type::WritableRef);
+    QEXPECT_FAIL(nullptr, "parser does not record const qualifier for auto types", Continue);
+    QCOMPARE(find.usages().at(22).type, Usage::Type::Read);
+
+    // Member function calls.
+    QCOMPARE(find.usages().at(23).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(24).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(25).type, Usage::Type::WritableRef);
+    QCOMPARE(find.usages().at(26).type, Usage::Type::Read);
+    QCOMPARE(find.usages().at(27).type, Usage::Type::WritableRef);
+
+    // Usages of struct type
+    find(structS);
+    QCOMPARE(find.usages().size(), 4);
+    QCOMPARE(find.usages().at(0).type, Usage::Type::Declaration);
+    QCOMPARE(find.usages().at(1).type, Usage::Type::Other);
+    QCOMPARE(find.usages().at(2).type, Usage::Type::Other);
+    QCOMPARE(find.usages().at(3).type, Usage::Type::Other);
 }
 
 QTEST_APPLESS_MAIN(tst_FindUsages)