Clang: Fix applying override declarations

Since https://reviews.llvm.org/D50898 (clang-8) libclang provides
override declarations when completing code in derived class scopes.

Applying such a completion item appended "()" and resulted in invalid
code, which is fixed with this change - the semicolon is inserted
instead now.

Change-Id: If2a04c5c719f62b98874f083a97445cd4e1db07d
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/clangcodemodel/clangassistproposalitem.cpp

@@ -151,6 +151,19 @@ static bool skipParenForFunctionLikeSnippet(const std::vector<int> &placeholderP
            && position + 1 == text.size();
 }
 
+static bool isFuncDeclAsSingleTypedText(const CodeCompletion &completion)
+{
+    // There is no libclang API to tell function call items from declaration items apart.
+    // However, the chunks differ for these items (c-index-test -code-completion-at=...):
+    //   An (override) declaration (available in derived class scope):
+    //     CXXMethod:{TypedText void hello() override} (40)
+    //   A function call:
+    //     CXXMethod:{ResultType void}{TypedText hello}{LeftParen (}{RightParen )} (36)
+    return completion.completionKind == CodeCompletion::FunctionDefinitionCompletionKind
+           && completion.chunks.size() == 1
+           && completion.chunks[0].kind == CodeCompletionChunk::TypedText;
+}
+
 void ClangAssistProposalItem::apply(TextDocumentManipulatorInterface &manipulator,
                                     int basePosition) const
 {
@@ -232,8 +245,12 @@ void ClangAssistProposalItem::apply(TextDocumentManipulatorInterface &manipulato
                 cursor.setPosition(basePosition);
                 abandonParen = QString("(;,{}").contains(prevChar);
             }
-            if (!abandonParen)
+            if (!abandonParen) {
-                abandonParen = isAtUsingDeclaration(manipulator, basePosition);
+                const bool isFullDecl = isFuncDeclAsSingleTypedText(ccr);
+                if (isFullDecl)
+                    extraCharacters += QLatin1Char(';');
+                abandonParen = isAtUsingDeclaration(manipulator, basePosition) || isFullDecl;
+            }
 
             if (!abandonParen && ccr.completionKind == CodeCompletion::FunctionDefinitionCompletionKind) {
                 const CodeCompletionChunk resultType = ccr.chunks.first();