[Diag-Experimental-Formatting] Custom formatting for Xcode editor placeholders

Author: owenv

lib/Frontend/PrintingDiagnosticConsumer.cpp

@@ -194,8 +194,22 @@ namespace {
     bool maybePrintInsertionAfter(int Byte, raw_ostream &Out) {
       for (auto fixIt : FixIts) {
         if ((int)fixIt.EndByte - 1 == Byte) {
-          Out.changeColor(ColoredStream::Colors::GREEN, true);
-          Out << fixIt.Text;
+          Out.changeColor(ColoredStream::Colors::GREEN, /*bold*/ true);
+          for (unsigned i = 0; i < fixIt.Text.size(); ++i) {
+            // Invert text colors for editor placeholders.
+            if (i + 1 < fixIt.Text.size() && fixIt.Text.substr(i, 2) == "<#") {
+              Out.changeColor(ColoredStream::Colors::GREEN, /*bold*/ true,
+                              /*background*/ true);
+              ++i;
+            } else if (i + 1 < fixIt.Text.size() &&
+                       fixIt.Text.substr(i, 2) == "#>") {
+              Out.changeColor(ColoredStream::Colors::GREEN, /*bold*/ true,
+                              /*background*/ false);
+              ++i;
+            } else {
+              Out << fixIt.Text[i];
+            }
+          }
           Out.resetColor();
           return true;
         }

test/diagnostics/pretty-printed-diagnostics.swift

@@ -34,6 +34,11 @@ extension A {
 
 let abc = "👍
 
+let x = {
+  let y = 1
+  return y
+}
+
 // Test fallback for non-ASCII characters.
 // CHECK: SOURCE_DIR/test/diagnostics/pretty-printed-diagnostics.swift:35:11
 // CHECK: 34 |
@@ -114,6 +119,11 @@ let abc = "👍
 // CHECK:    |                ^ note: Remove '=' to make 'x' a computed property [remove '= '] [replace 'let' with 'var']
 // CHECK: 33 | }
 
+// CHECK: SOURCE_DIR/test/diagnostics/pretty-printed-diagnostics.swift:37:9
+// CHECK: 36 |
+// CHECK: 37 | let x = { () -> Result in
+// CHECK:    |         ^ error: unable to infer complex closure return type; add explicit type to disambiguate
+// CHECK: 38 |   let y = 1
 
 // CHECK: SOURCE_DIR/test/diagnostics/pretty-printed-diagnostics.swift:6:5
 // CHECK: 5 | func foo(a: Int, b: Int) {