[Diagnostics] Use the new swift-syntax formatter for -diagnostic-style swift.

We're going to move toward the new swift-syntax formatter. Use it for
the "swift" diagnostic style instead of the experimental formatter
written in C++.

There are some tests for the experimental formatter in C++ that test
precise formatting of diagnostics. I've disabled them in the same
places where the new swift-syntax formatter is enabled, for now. We
may choose to remove them entirely, because swift-syntax itself is
where the specific format is defined, and has those same kinds of
tests already.

Author: DougGregor

include/swift/Basic/DiagnosticOptions.h

@@ -32,7 +32,7 @@ class DiagnosticOptions {
     VerifyAndApplyFixes
   } VerifyMode = NoVerify;
 
-  enum FormattingStyle { LLVM, Swift, SwiftSyntax };
+  enum FormattingStyle { LLVM, Swift };
 
   /// Indicates whether to allow diagnostics for \c <unknown> locations if
   /// \c VerifyMode is not \c NoVerify.

lib/Frontend/CompilerInvocation.cpp

@@ -1517,9 +1517,6 @@ static bool ParseDiagnosticArgs(DiagnosticOptions &Opts, ArgList &Args,
       Opts.PrintedFormattingStyle = DiagnosticOptions::FormattingStyle::LLVM;
     } else if (contents == "swift") {
       Opts.PrintedFormattingStyle = DiagnosticOptions::FormattingStyle::Swift;
-    } else if (contents == "swift-syntax") {
-      Opts.PrintedFormattingStyle =
-          DiagnosticOptions::FormattingStyle::SwiftSyntax;
     } else {
       Diags.diagnose(SourceLoc(), diag::error_unsupported_option_argument,
                      arg->getOption().getPrefixedName(), arg->getValue());

lib/Frontend/PrintingDiagnosticConsumer.cpp

@@ -1101,8 +1101,9 @@ void PrintingDiagnosticConsumer::handleDiagnostic(SourceManager &SM,
     return;
 
   switch (FormattingStyle) {
-  case DiagnosticOptions::FormattingStyle::SwiftSyntax: {
+  case DiagnosticOptions::FormattingStyle::Swift: {
 #if SWIFT_SWIFT_PARSER
+    // Use the swift-syntax formatter.
     auto bufferStack = getSourceBufferStack(SM, Info.Loc);
     if (!bufferStack.empty()) {
       // If there are no enqueued diagnostics, or they are from a different
@@ -1121,34 +1122,38 @@ void PrintingDiagnosticConsumer::handleDiagnostic(SourceManager &SM,
       enqueueDiagnostic(queuedDiagnostics, Info, SM);
       break;
     }
+#endif
+
+    // Use the C++ formatter.
+    // FIXME: Once the swift-syntax formatter is enabled everywhere, we will
+    // remove this.
+    if (Info.Loc.isValid()) {
+      if (Info.Kind == DiagnosticKind::Note && currentSnippet) {
+        // If this is a note and we have an in-flight message, add it to that
+        // instead of emitting it separately.
+        annotateSnippetWithInfo(SM, Info, *currentSnippet);
+      } else {
+        // If we encounter a new error/warning/remark, flush any in-flight
+        // snippets.
+        flush(/*includeTrailingBreak*/ true);
+        currentSnippet = std::make_unique<AnnotatedSourceSnippet>(SM);
+        annotateSnippetWithInfo(SM, Info, *currentSnippet);
+      }
+      if (PrintEducationalNotes) {
+        for (auto path : Info.EducationalNotePaths) {
+          if (auto buffer = SM.getFileSystem()->getBufferForFile(path))
+            BufferedEducationalNotes.push_back(buffer->get()->getBuffer().str());
+        }
+      }
+      break;
+    }
 
     // Fall through to print using the LLVM style when there is no source
     // location.
     flush(/*includeTrailingBreak*/ false);
-#endif
     LLVM_FALLTHROUGH;
   }
 
-  case DiagnosticOptions::FormattingStyle::Swift:
-    if (Info.Kind == DiagnosticKind::Note && currentSnippet) {
-      // If this is a note and we have an in-flight message, add it to that
-      // instead of emitting it separately.
-      annotateSnippetWithInfo(SM, Info, *currentSnippet);
-    } else {
-      // If we encounter a new error/warning/remark, flush any in-flight
-      // snippets.
-      flush(/*includeTrailingBreak*/ true);
-      currentSnippet = std::make_unique<AnnotatedSourceSnippet>(SM);
-      annotateSnippetWithInfo(SM, Info, *currentSnippet);
-    }
-    if (PrintEducationalNotes) {
-      for (auto path : Info.EducationalNotePaths) {
-        if (auto buffer = SM.getFileSystem()->getBufferForFile(path))
-          BufferedEducationalNotes.push_back(buffer->get()->getBuffer().str());
-      }
-    }
-    break;
-
   case DiagnosticOptions::FormattingStyle::LLVM:
     printDiagnostic(SM, Info);
 

test/diagnostics/educational-notes.swift

@@ -1,6 +1,5 @@
 // RUN: not %target-swift-frontend -color-diagnostics -diagnostic-style=llvm -print-educational-notes -diagnostic-documentation-path %S/test-docs/ -typecheck %s 2>&1 | %FileCheck %s --match-full-lines --strict-whitespace
 // RUN: not %target-swift-frontend -no-color-diagnostics -print-educational-notes -diagnostic-documentation-path %S/test-docs/ -typecheck %s 2>&1 | %FileCheck %s --match-full-lines --strict-whitespace --check-prefix=NO-COLOR
-// RUN: not %target-swift-frontend -diagnostic-style=swift -print-educational-notes -diagnostic-documentation-path %S/test-docs/ -typecheck %s 2>&1 | %FileCheck %s --check-prefix=CHECK-DESCRIPTIVE
 
 // A diagnostic with no educational notes
 let x = 1 +

test/diagnostics/pretty-printed-diagnostics.swift

@@ -1,5 +1,8 @@
 // RUN: not %target-swift-frontend -diagnostic-style=swift -typecheck %/s 2>&1 | %FileCheck %s
 
+// Note: test has not been updated to match the swift-syntax style.
+// XFAIL: OS=macosx
+
 1 + 2
 
 func foo(a: Int, b: Int) {

test/diagnostics/pretty-printed-diags-in-clang-buffer.swift

@@ -1,5 +1,8 @@
 // RUN: not %target-swift-frontend -diagnostic-style=swift -typecheck %/s 2>&1 | %FileCheck %s
 
+// Note: test has not been updated to match the swift-syntax style.
+// XFAIL: OS=macosx
+
 // Error split between the real file and a virtual one.
 #sourceLocation(file: "abc.swift", line: 9)
 let x = 1