ClangCodeModel: Show value in tool tips, if possible

When hovering over a constant expression, it's probably helpful
to show that value to the user.
Requires clang 11 to fully work. For now, it only shows the value for
variable initializations.

Fixes: QTCREATORBUG-23967
Change-Id: I6b844231bac50993c2fa2fa82c552ad9cef590df
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/libs/clangsupport/tooltipinfo.h

@@ -28,6 +28,8 @@
 #include <utf8string.h>
 #include <utf8stringvector.h>
 
+#include <QVariant>
+
 namespace ClangBackEnd {
 
 class ToolTipInfo
@@ -54,6 +56,7 @@ public:
         out << message.qdocIdCandidates;
         out << message.qdocMark;
         out << static_cast<quint8>(message.qdocCategory);
+        out << message.value;
         out << message.sizeInBytes;
 
         return out;
@@ -68,6 +71,7 @@ public:
         in >> message.qdocIdCandidates;
         in >> message.qdocMark;
         in >> qdocCategory;
+        in >> message.value;
         in >> message.sizeInBytes;
 
         message.qdocCategory = static_cast<QdocCategory>(qdocCategory);
@@ -82,6 +86,7 @@ public:
             && first.qdocIdCandidates == second.qdocIdCandidates
             && first.qdocMark == second.qdocMark
             && first.qdocCategory == second.qdocCategory
+            && first.value == second.value
             && first.sizeInBytes == second.sizeInBytes;
     }
 
@@ -92,6 +97,7 @@ public:
     Utf8StringVector qdocIdCandidates;
     Utf8String qdocMark;
     QdocCategory qdocCategory = Unknown;
+    QVariant value;
 
     // For class definition and for class fields.
     Utf8String sizeInBytes;

src/plugins/clangcodemodel/clangbackendreceiver.cpp

@@ -339,7 +339,7 @@ static CppTools::ToolTipInfo toToolTipInfo(const ToolTipMessage &message)
     info.qDocIdCandidates = toStringList(backendInfo.qdocIdCandidates);
     info.qDocMark = backendInfo.qdocMark;
     info.qDocCategory = toHelpItemCategory(backendInfo.qdocCategory);
-
+    info.value = backendInfo.value;
     info.sizeInBytes = backendInfo.sizeInBytes;
 
     return info;

src/plugins/clangcodemodel/clanghoverhandler.cpp

@@ -181,6 +181,22 @@ void ClangHoverHandler::processToolTipInfo(const CppTools::ToolTipInfo &info)
 
     if (!info.sizeInBytes.isEmpty())
         text.append("\n\n" + tr("%1 bytes").arg(info.sizeInBytes));
+    if (info.value.isValid()) {
+        text.append("\n\n" + tr("Value: "));
+        switch (info.value.type()) {
+        case static_cast<QVariant::Type>(QMetaType::LongLong):
+            text.append(QString::number(info.value.toLongLong()));
+            break;
+        case static_cast<QVariant::Type>(QMetaType::ULongLong):
+            text.append(QString::number(info.value.toULongLong()));
+            break;
+        case static_cast<QVariant::Type>(QMetaType::Double):
+            text.append(QString::number(info.value.toDouble()));
+            break;
+        default:
+            QTC_CHECK(false);
+        }
+    }
 
     setToolTip(text);
     m_reportPriority(priority());

src/plugins/cpptools/baseeditordocumentprocessor.h

@@ -41,6 +41,8 @@
 
 #include <QTextEdit>
 
+#include <QVariant>
+
 #include <functional>
 
 namespace TextEditor {
@@ -57,6 +59,7 @@ struct CPPTOOLS_EXPORT ToolTipInfo {
     QStringList qDocIdCandidates;
     QString qDocMark;
     Core::HelpItem::Category qDocCategory;
+    QVariant value;
 
     QString sizeInBytes;
 };

src/tools/clangbackend/source/clangtooltipinfocollector.cpp

@@ -149,6 +149,28 @@ Utf8String sizeInBytes(const Cursor &cursor)
     return Utf8String();
 }
 
+QVariant value(const Cursor &cursor)
+{
+    if (!clang_isDeclaration(cursor.cx().kind) && !clang_isExpression(cursor.cx().kind))
+        return {};
+    const CXEvalResult evalResult = clang_Cursor_Evaluate(cursor.cx());
+    QVariant v;
+    switch (clang_EvalResult_getKind(evalResult)) {
+    case CXEval_Int:
+        v = clang_EvalResult_isUnsignedInt(evalResult)
+                ? QVariant::fromValue(clang_EvalResult_getAsUnsigned(evalResult))
+                : QVariant::fromValue(clang_EvalResult_getAsLongLong(evalResult));
+        break;
+    case CXEval_Float:
+        v = QVariant::fromValue(clang_EvalResult_getAsDouble(evalResult));
+        break;
+    default:
+        break;
+    }
+    clang_EvalResult_dispose(evalResult);
+    return v;
+}
+
 Cursor referencedCursor(const Cursor &cursor)
 {
     // Query the referenced cursor directly instead of first testing with cursor.isReference().
@@ -503,6 +525,7 @@ ToolTipInfo ToolTipInfoCollector::collect(uint line, uint column) const
     ToolTipInfo info;
     info.text = text(cursor, referenced);
     info.briefComment = referenced.briefComment();
+    info.value = value(cursor);
 
     {
         ToolTipInfo qDocToolTipInfo = qDocInfo(referenced);

tests/unit/unittest/clangtooltipinfo-test.cpp

@@ -385,6 +385,15 @@ TEST_F(ToolTipInfo, SizeForUnion)
     ASSERT_THAT(actual.sizeInBytes, Utf8StringLiteral("1"));
 }
 
+TEST_F(ToolTipInfo, constexprValue)
+{
+    // CLANG-UPGRADE-CHECK: Adapt the values below
+    ASSERT_THAT(tooltip(204, 12).value.toInt(), 4);
+    ASSERT_THAT(tooltip(204, 27).value.toInt(), 4); // 3 in clang 11
+    ASSERT_THAT(tooltip(204, 30).value.toInt(), 4);
+    ASSERT_THAT(tooltip(204, 32).value.toInt(), 4); // 1 in clang 11
+}
+
 TEST_F(ToolTipInfo, Namespace)
 {
     ::ToolTipInfo expected(Utf8StringLiteral("X"));

tests/unit/unittest/data/tooltipinfo.cpp

@@ -199,3 +199,6 @@ Nuu **pointers(Nuu **p1)
 {
     return p1;
 }
+
+static constexpr int calcValue() { return 1 + 2; }
+const auto val = calcValue() + sizeof(char);