[clang] [NFC][Clang] Use range for loops in ClangDiagnosticsEmitter (PR #115573)

[Rahul Joshi via cfe-commits]

================
@@ -185,10 +174,8 @@ static void groupDiagnostics(ArrayRef<const Record *> Diags,
   }
 
   // Assign unique ID numbers to the groups.
-  unsigned IDNo = 0;
-  for (std::map<std::string, GroupInfo>::iterator
-       I = DiagsInGroup.begin(), E = DiagsInGroup.end(); I != E; ++I, ++IDNo)
-    I->second.IDNo = IDNo;
+  for (auto [IdNo, Iter] : enumerate(DiagsInGroup))
+    Iter.second.IDNo = IdNo;
----------------
jurahul wrote:

Right, this updates the original and not the copy. See the comment at the top of enumerate() which says the same:

https://github.com/llvm/llvm-project/blob/main/llvm/include/llvm/ADT/STLExtras.h#L2411

```
/// Given two or more input ranges, returns a new range whose values are
/// tuples (A, B, C, ...), such that A is the 0-based index of the item in the
/// sequence, and B, C, ..., are the values from the original input ranges. All
/// input ranges are required to have equal lengths. Note that the returned
/// iterator allows for the values (B, C, ...) to be modified.
```

https://github.com/llvm/llvm-project/pull/115573