https://issues.dlang.org/show_bug.cgi?id=24675

          Issue ID: 24675
           Summary: Allow variable declarations in `for`conditions
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: qs.il.paperinik@gmail.com

A `for` loop essentially is syntax sugar for a `while` loop, except that a `while` loop can declare a variable in its condition, but a `for` loop can’t.

A variable declared in the condition can be mimicked:
```d
for (int i; int diff = 5 - i; ++i) { } // error
for ({int i; int diff; } (diff = 5 - i) == true; ++i) { }
```

Grammar change:
```diff
  ForStatement:
-     for ( Initialize Test? ; Increment? ) ScopeStatement
+     for ( Initialize IfCondition? ; Increment? ) ScopeStatement

- Test:
-     Expression
```

Not also that declarations in `for` conditions are allowed in C++.

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