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

[Rahul Joshi via cfe-commits]

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@@ -1553,15 +1526,13 @@ static void emitDiagSubGroups(std::map<std::string, GroupInfo> &DiagsInGroup,
                               RecordVec &GroupsInPedantic, raw_ostream &OS) {
   OS << "static const int16_t DiagSubGroups[] = {\n"
      << "  /* Empty */ -1,\n";
-  for (auto const &I : DiagsInGroup) {
-    const bool IsPedantic = I.first == "pedantic";
-
-    const std::vector<std::string> &SubGroups = I.second.SubGroups;
+  for (auto const &[Name, Group] : DiagsInGroup) {
+    const bool IsPedantic = Name == "pedantic";
+    const std::vector<std::string> &SubGroups = Group.SubGroups;
     if (!SubGroups.empty() || (IsPedantic && !GroupsInPedantic.empty())) {
-      OS << "  /* DiagSubGroup" << I.second.IDNo << " */ ";
+      OS << "  /* DiagSubGroup" << Group.IDNo << " */ ";
       for (auto const &SubGroup : SubGroups) {
-        std::map<std::string, GroupInfo>::const_iterator RI =
-            DiagsInGroup.find(SubGroup);
+        auto RI = DiagsInGroup.find(SubGroup);
----------------
jurahul wrote:

Is it prohibited? Reading the coding standard, I see:

```
Another time when auto works well for these purposes is when the type would have been abstracted away anyways, often behind a container’s typedef such as std::vector<T>::iterator.
```

I've seen auto used for such iterators all over the place in LLVM codebase.

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