QmlJS: Restrict warnings of blocks

Warn only if the block contains a var statement
as this is discouraged.

Fixes: QTCREATORBUG-24214
Change-Id: Ib96c6723e82b6ddce0b7b63f23d3408f45ae7d58
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/libs/qmljs/qmljscheck.cpp

@@ -1367,7 +1367,8 @@ bool Check::visit(Block *ast)
                 && !cast<IfStatement *>(p)
                 && !cast<SwitchStatement *>(p)
                 && !isCaseOrDefault(p)
-                && !cast<WithStatement *>(p)) {
+                && !cast<WithStatement *>(p)
+                && hasVarStatement(ast)) {
             addMessage(WarnBlock, ast->lbraceToken);
         }
         if (!ast->statements
@@ -1666,6 +1667,24 @@ bool Check::isCaseOrDefault(Node *n)
     return false;
 }
 
+bool Check::hasVarStatement(AST::Block *b) const
+{
+    QTC_ASSERT(b, return false);
+    StatementList *s = b->statements;
+    while (s) {
+        if (auto var = cast<VariableStatement *>(s->statement)) {
+            VariableDeclarationList *declList = var->declarations;
+            while (declList) {
+                if (declList->declaration && declList->declaration->scope == VariableScope::Var)
+                    return true;
+                declList = declList->next;
+            }
+        }
+        s = s->next;
+    }
+    return false;
+}
+
 bool Check::visit(NewExpression *ast)
 {
     checkNewExpression(ast->expression);

src/libs/qmljs/qmljscheck.h

@@ -123,6 +123,7 @@ private:
     bool isQtQuick2Ui() const;
 
     bool isCaseOrDefault(AST::Node *n);
+    bool hasVarStatement(AST::Block *b) const;
 
     AST::Node *parent(int distance = 0);