Highlight inline as a "soft" keyword

Author: allanrenucci

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -1223,7 +1223,7 @@ object Parsers {
               val t = postfixExpr()
               if (in.token == MATCH) matchExpr(t, start, InlineMatch)
               else {
-                syntaxErrorOrIncomplete("`match` or `if` expected but ${in.token} found")
+                syntaxErrorOrIncomplete(s"`match` or `if` expected but ${showToken(in.token)} found")
                 t
               }
           }

compiler/src/dotty/tools/dotc/printing/SyntaxHighlighting.scala

@@ -62,14 +62,22 @@ object SyntaxHighlighting {
         token match {
           case _ if literalTokens.contains(token) =>
             highlightRange(start, end, LiteralColor)
+
           case STRINGPART =>
             // String interpolation parts include `$` but
             // we don't highlight it, hence the `-1`
             highlightRange(start, end - 1, LiteralColor)
+
           case _ if alphaKeywords.contains(token) =>
             highlightRange(start, end, KeywordColor)
+
+          case IDENTIFIER if name == nme.INLINEkw =>
+            // `inline` is a "soft" keyword
+            highlightRange(start, end, KeywordColor)
+
           case IDENTIFIER if name == nme.??? =>
             highlightRange(start, end, Console.RED_B)
+
           case _ =>
         }
       }

compiler/test/dotty/tools/dotc/printing/SyntaxHighlightingTests.scala

@@ -120,4 +120,11 @@ class SyntaxHighlightingTests extends DottyTest {
     test("val foo @ Foo(x) = bar", ???)
     test("x match { case Foo | Bar => 1 }", ???)
   }
+
+  @Test
+  def softKeywords = {
+    test("inline def foo = 1", "<K|inline> <K|def> <V|foo> = <L|1>")
+    test("@inline def foo = 1", "<T|@inline> <K|def> <V|foo> = <L|1>")
+    test("class inline", "<K|class> <T|inline>")
+  }
 }