[clang][NFC] Refactor emitSnippet()

[tbaeder]

Summary

Rename parameters and local variables and reorder things a bit to be closer to their first point of use.
This doesn't change anything else.

[tbaeder]

Side-note: The ToPrint stuff here is just useful to "cache" the output string, isn't it? Is that really useful? I'd expect the output stream to be cached anyway?

[aaron.ballman]

In D150840#4359570, @tbaeder wrote:

Side-note: The ToPrint stuff here is just useful to "cache" the output string, isn't it? Is that really useful? I'd expect the output stream to be cached anyway?

Yeah, that does seem like a kind of caching operation, I'm not certain what it's purpose is though.

LGTM!

clang/lib/Frontend/TextDiagnostic.cpp

if (!FixItInsertionLine.empty()) {
         OS.resetColor();
     }
   }
 
   // Print out any parseable fixit information requested by the options.
   emitParseableFixits(Hints, SM);
 }
 
-void TextDiagnostic::emitSnippet(StringRef line, unsigned MaxLineNoDisplayWidth,
+void TextDiagnostic::emitSnippet(StringRef SourceLine,
+                                 unsigned MaxLineNoDisplayWidth,
                                  unsigned LineNo) {
-  if (line.empty())
+  if (SourceLine.empty())
     return;
 
-  size_t i = 0;
-
-  std::string to_print;
-  bool print_reversed = false;
-
   // Emit line number.
   if (MaxLineNoDisplayWidth > 0) {
     unsigned LineNoDisplayWidth = getNumDisplayWidth(LineNo);
     OS << ' ';
     for (unsigned I = LineNoDisplayWidth; I < MaxLineNoDisplayWidth; ++I)
       OS << ' ';
     OS << LineNo;
     OS << " | ";
   }
 
-  while (i<line.size()) {
-    std::pair<SmallString<16>,bool> res
-        = printableTextForNextCharacter(line, &i, DiagOpts->TabStop);
-    bool was_printable = res.second;
+  bool PrintReversed = false;
+  std::string ToPrint;
+  size_t I = 0;
+  while (I < SourceLine.size()) {
+    auto [Str, WasPrintable] =
+        printableTextForNextCharacter(SourceLine, &I, DiagOpts->TabStop);
 
-    if (DiagOpts->ShowColors && was_printable == print_reversed) {
-      if (print_reversed)
+    if (DiagOpts->ShowColors && WasPrintable == PrintReversed) {
+      if (PrintReversed)
         OS.reverseColor();
-      OS << to_print;
-      to_print.clear();
+      OS << ToPrint;
+      ToPrint.clear();
       if (DiagOpts->ShowColors)
         OS.resetColor();
     }
 
-    print_reversed = !was_printable;
-    to_print += res.first.str();
+    PrintReversed = !WasPrintable;
+    ToPrint += Str;
   }
 
-  if (print_reversed && DiagOpts->ShowColors)
+  if (PrintReversed && DiagOpts->ShowColors)
     OS.reverseColor();
-  OS << to_print;
-  if (print_reversed && DiagOpts->ShowColors)
+  OS << ToPrint;
+  if (PrintReversed && DiagOpts->ShowColors)
     OS.resetColor();
 
   OS << '\n';
 }
 
 void TextDiagnostic::emitParseableFixits(ArrayRef<FixItHint> Hints,
                                          const SourceManager &SM) {
   if (!DiagOpts->ShowParseableFixits)