SI-8888 Avoid ClassFormatError under -Ydelambdafy:method

The pattern matcher phase (conceivably, among others) can generate
code that binds local `Ident`s symbolically, rather than according
to the lexical scope. This means that a lambda can capture more than
one local of the same name.

In the enclosed test case, this ends up creating the following
tree after delambdafy

    [[syntax trees at end of                delambdafy]] // delambday-patmat-path-dep.scala
    matchEnd4({
      case <synthetic> val x1: Object = (x2: Object);
      case5(){
        if (x1.$isInstanceOf[C]())
          {
            <synthetic> val x2#19598: C = (x1.$asInstanceOf[C](): C);
            matchEnd4({
              {
                (new resume$1(x2#19598, x2#19639): runtime.AbstractFunction0)
              };
              scala.runtime.BoxedUnit.UNIT
            })
          }
        else
          case6()
      };
      ...
    })
    ...
    <synthetic> class resume$1 extends AbstractFunction0 {
      <synthetic> var x2: C = null;
      <synthetic> var x2: C = null;
      ...
    }

After this commit, the var members of `resume$1` are given fresh
names, rather than directly using the name of the captured var:

    <synthetic> var x2$3: C = null;
    <synthetic> var x2$4: C = null;

1 files changed, 1 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/Delambdafy.scala b/src/compiler/scala/tools/nsc/transform/Delambdafy.scala
index 12e7b23f48..835d338ab3 100644
--- a/src/compiler/scala/tools/nsc/transform/Delambdafy.scala
+++ b/src/compiler/scala/tools/nsc/transform/Delambdafy.scala
@@ -260,7 +260,7 @@ abstract class Delambdafy extends Transform with TypingTransformers with ast.Tre
 
         val captureProxies2 = new LinkedHashMap[Symbol, TermSymbol]
         captures foreach {capture =>
-          val sym = lambdaClass.newVariable(capture.name.toTermName, capture.pos, SYNTHETIC)
+          val sym = lambdaClass.newVariable(unit.freshTermName(capture.name.toString + "$"), capture.pos, SYNTHETIC)
           sym setInfo capture.info
           captureProxies2 += ((capture, sym))
         }