Postponing desugaring of Try nodes.

Instead of desugaring in parser desugaring is now done during desugaring.

Author: DarkDimius

Diff for: src/dotty/tools/dotc/ast/Desugar.scala

@@ -817,6 +817,16 @@ object desugar {
       case PatDef(mods, pats, tpt, rhs) =>
         val pats1 = if (tpt.isEmpty) pats else pats map (Typed(_, tpt))
         flatTree(pats1 map (makePatDef(mods, _, rhs)))
+      case ParsedTry(body, handler, finalizer) =>
+        handler match {
+          case Match(EmptyTree, cases) => Try(body, cases, finalizer)
+          case EmptyTree => Try(body, Nil, finalizer)
+          case _ =>
+            Try(body,
+              List(CaseDef(Ident(nme.DEFAULT_EXCEPTION_NAME), EmptyTree, Apply(handler, Ident(nme.DEFAULT_EXCEPTION_NAME)))),
+              finalizer)
+        }
+
     }
   }.withPos(tree.pos)
 

Diff for: src/dotty/tools/dotc/ast/untpd.scala

@@ -32,6 +32,8 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
     def withName(name: Name)(implicit ctx: Context) = cpy.ModuleDef(this)(mods, name.toTermName, impl)
   }
 
+  case class ParsedTry(expr: Tree, handler: Tree, finalizer: Tree) extends TermTree
+
   case class SymbolLit(str: String) extends TermTree
   case class InterpolatedString(id: TermName, strings: List[Literal], elems: List[Tree]) extends TermTree
   case class Function(args: List[Tree], body: Tree) extends Tree {

Diff for: src/dotty/tools/dotc/parsing/Parsers.scala

@@ -914,15 +914,7 @@ object Parsers {
           val finalizer =
             if (handler.isEmpty || in.token == FINALLY) { accept(FINALLY); expr() }
             else EmptyTree
-          handler match {
-            case Match(sel, cases) => Try(body, cases, finalizer)
-            case EmptyTree => Try(body, Nil, finalizer)
-            case _ =>
-              Try(body,
-                List(CaseDef(Ident(nme.DEFAULT_EXCEPTION_NAME), EmptyTree, Apply(handler, Ident(nme.DEFAULT_EXCEPTION_NAME)))),
-              finalizer)
-          }
-
+          ParsedTry(body, handler, finalizer)
         }
       case THROW =>
         atPos(in.skipToken()) { Throw(expr()) }