From 5b8327b807c40cab867065cf695191a36c9210ee Mon Sep 17 00:00:00 2001
From: Jason Zaugg <jzaugg@gmail.com>
Date: Tue, 7 May 2013 23:29:02 +0200
Subject: SI-7459 Handle pattern binders used as prefixes in TypeTrees.

Match translation was incorrect for:

    case t => new t.C
    case D(t) => new d.C

We would end up with Types in TypeTrees referring to the wrong
symbols, e.g:

    // t7459a.scala
    ((x0$1: this.LM) => {
      case <synthetic> val x1: this.LM = x0$1;
      case4(){
       matchEnd3(new tttt.Node[Any]())
      };
      matchEnd3(x: Any){
        x
    }

Or:
    // t7459b.scala
     ((x0$1: CC) => {
       case <synthetic> val x1: CC = x0$1;
       case4(){
         if (x1.ne(null))
           matchEnd3(new tttt.Node[Any]())
         else
           case5()
       };

This commit:

  - Changes `bindSubPats` to traverse types, as well as terms,
    in search of references to bound symbols
  - Changes `Substitution` to reuse `Tree#substituteSymbols` rather
    than the home-brew substitution from `Tree`s to `Tree`s, if the
    `to` trees are all `Ident`s
  - extends `substIdentsForTrees` to substitute selections like
    `x1.caseField` into types.

I had to dance around the awkward handling of "swatches" (exception
handlers that can be implemented with JVM native type switches) by
duplicating trees to avoid seeing the results of `substituteSymbols`
in `caseDefs` after we abandon that approach if we detect the
patterns are too complex late in the game.

I also had to add an escape hatch for the "type selection from
volatile type" check in the type checker. Without this, the
translation of `pos/t7459c.scala`:

    case <synthetic> val x1: _$1 = (null: Test.Mirror[_]).universe;
    case5(){
      if (x1.isInstanceOf[Test.JavaUniverse])
        {
          <synthetic> val x2: _$1 with Test.JavaUniverse = (x1.asInstanceOf[_$1 with Test.JavaUniverse]: _$1 with Test.JavaUniverse);
          matchEnd4({
            val ju1: Test.JavaUniverse = x2;
            val f: () => x2.Type = (() => (null: x2.TypeTag[Nothing]).tpe);

.. triggers that error at `x2.TypeTag`.
---
 test/files/pos/t7459a.scala | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 test/files/pos/t7459a.scala

(limited to 'test/files/pos/t7459a.scala')

diff --git a/test/files/pos/t7459a.scala b/test/files/pos/t7459a.scala
new file mode 100644
index 0000000000..5107715e06
--- /dev/null
+++ b/test/files/pos/t7459a.scala
@@ -0,0 +1,18 @@
+trait SpecialException extends Throwable
+
+object Test {
+  def run() {
+    try {
+      ???
+    } catch {
+      case e: SpecialException => e.isInstanceOf[SpecialException]
+      case e =>
+    }
+
+    // OKAY
+    // (null: Throwable) match {
+    //   case e: SpecialException => e.isInstanceOf[SpecialException]
+    //   case e =>
+    // }
+  }
+}
\ No newline at end of file
-- 
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