CppEditor: Add support for init statements in if conditions

Fixes: QTCREATORBUG-29182
Change-Id: I9b7969da694b368236246123ad0028d8e754e903
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

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

@@ -1779,6 +1779,8 @@ public:
     int if_token = 0;
     int constexpr_token = 0;
     int lparen_token = 0;
+    DeclarationAST *initDecl = nullptr;
+    StatementAST *initStmt = nullptr;
     ExpressionAST *condition = nullptr;
     int rparen_token = 0;
     StatementAST *statement = nullptr;

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

@@ -785,6 +785,10 @@ IfStatementAST *IfStatementAST::clone(MemoryPool *pool) const
     ast->if_token = if_token;
     ast->constexpr_token = constexpr_token;
     ast->lparen_token = lparen_token;
+    if (initDecl)
+        ast->initDecl = initDecl->clone(pool);
+    if (initStmt)
+        ast->initStmt = initStmt->clone(pool);
     if (condition)
         ast->condition = condition->clone(pool);
     ast->rparen_token = rparen_token;

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

@@ -1318,6 +1318,16 @@ bool ASTMatcher::match(IfStatementAST *node, IfStatementAST *pattern)
 
     pattern->lparen_token = node->lparen_token;
 
+    if (!pattern->initDecl)
+        pattern->initDecl = node->initDecl;
+    else if (!AST::match(node->initDecl, pattern->initDecl, this))
+        return false;
+
+    if (!pattern->initStmt)
+        pattern->initStmt = node->initStmt;
+    else if (!AST::match(node->initStmt, pattern->initStmt, this))
+        return false;
+
     if (! pattern->condition)
         pattern->condition = node->condition;
     else if (! AST::match(node->condition, pattern->condition, this))

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

@@ -563,6 +563,8 @@ void ForStatementAST::accept0(ASTVisitor *visitor)
 void IfStatementAST::accept0(ASTVisitor *visitor)
 {
     if (visitor->visit(this)) {
+        accept(initDecl, visitor);
+        accept(initStmt, visitor);
         accept(condition, visitor);
         accept(statement, visitor);
         accept(else_statement, visitor);

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

@@ -1528,6 +1528,10 @@ bool Bind::visit(IfStatementAST *ast)
     ast->symbol = block;
 
     Scope *previousScope = switchScope(block);
+    if (ast->initDecl)
+        this->declaration(ast->initDecl);
+    else if (ast->initStmt)
+        this->statement(ast->initStmt);
     /*ExpressionTy condition =*/ this->expression(ast->condition);
     this->statement(ast->statement);
     this->statement(ast->else_statement);

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

@@ -3511,12 +3511,14 @@ bool Parser::parseExpressionStatement(StatementAST *&node)
 
     ExpressionAST *expression = nullptr;
     if (parseExpression(expression)) {
-        ExpressionStatementAST *ast = new (previousPool) ExpressionStatementAST;
+        if (LA() == T_SEMICOLON) {
-        if (expression)
+            ExpressionStatementAST *ast = new (previousPool) ExpressionStatementAST;
-            ast->expression = expression->clone(previousPool);
+            ast->semicolon_token = consumeToken();
-        match(T_SEMICOLON, &ast->semicolon_token);
+            if (expression)
-        node = ast;
+                ast->expression = expression->clone(previousPool);
-        parsed = true;
+            node = ast;
+            parsed = true;
+        }
     }
 
     _inExpressionStatement = wasInExpressionStatement;
@@ -4072,6 +4074,19 @@ bool Parser::parseIfStatement(StatementAST *&node)
             ast->constexpr_token = consumeToken();
         }
         match(T_LPAREN, &ast->lparen_token);
+
+        // C++17: init-statement
+        if (_languageFeatures.cxx17Enabled) {
+            const int savedCursor = cursor();
+            const bool savedBlockErrors = _translationUnit->blockErrors(true);
+            if (!parseSimpleDeclaration(ast->initDecl)) {
+                rewind(savedCursor);
+                if (!parseExpressionStatement(ast->initStmt))
+                    rewind(savedCursor);
+            }
+            _translationUnit->blockErrors(savedBlockErrors);
+        }
+
         parseCondition(ast->condition);
         match(T_RPAREN, &ast->rparen_token);
         if (! parseStatement(ast->statement))

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

@@ -455,6 +455,7 @@ struct LanguageFeatures
             unsigned int cxxEnabled : 1;
             unsigned int cxx11Enabled : 1;
             unsigned int cxx14Enabled : 1;
+            unsigned int cxx17Enabled : 1;
             unsigned int cxx20Enabled : 1;
             unsigned int objCEnabled : 1;
             unsigned int c99Enabled : 1;

src/plugins/cppeditor/projectpart.cpp

@@ -163,6 +163,7 @@ CPlusPlus::LanguageFeatures ProjectPart::deriveLanguageFeatures() const
     CPlusPlus::LanguageFeatures features;
     features.cxx11Enabled = languageVersion >= Utils::LanguageVersion::CXX11;
     features.cxx14Enabled = languageVersion >= Utils::LanguageVersion::CXX14;
+    features.cxx17Enabled = languageVersion >= Utils::LanguageVersion::CXX17;
     features.cxx20Enabled = languageVersion >= Utils::LanguageVersion::CXX20;
     features.cxxEnabled = hasCxx;
     features.c99Enabled = languageVersion >= Utils::LanguageVersion::C99;

tests/auto/cplusplus/cxx11/tst_cxx11.cpp

@@ -150,6 +150,7 @@ private Q_SLOTS:
     void requiresClause();
     void coroutines();
     void genericLambdas();
+    void ifStatementWithInitialization();
 };
 
 
@@ -550,5 +551,27 @@ int main()
     QVERIFY(!hasErrors);
 }
 
+void tst_cxx11::ifStatementWithInitialization()
+{
+    LanguageFeatures features;
+    features.cxxEnabled = true;
+    features.cxx11Enabled = features.cxx14Enabled = features.cxx17Enabled = true;
+
+    const QString source = R"(
+int main()
+{
+    if (bool b = true; b)
+        b = false;
+}
+)";
+    QByteArray errors;
+    Document::Ptr doc = Document::create(FilePath::fromPathPart(u"testFile"));
+    processDocument(doc, source.toUtf8(), features, &errors);
+    const bool hasErrors = !errors.isEmpty();
+    if (hasErrors)
+        qDebug().noquote() << errors;
+    QVERIFY(!hasErrors);
+}
+
 QTEST_APPLESS_MAIN(tst_cxx11)
 #include "tst_cxx11.moc"