Debug info: don't conflate generators and loop variable bindings.

<rdar://problem/17058606> for loop range variable shares name with iteration counter - that's wrong and misleading
<rdar://problem/16786106> [Xcode 6.1] foreach generators are always named "$generator"

Swift SVN r20683

lib/Sema/TypeCheckStmt.cpp

@@ -426,13 +426,9 @@ public:
       if (!getGenerator) return nullptr;
       
       // Create a local variable to capture the generator.
-      StringRef name = "$generator";
+      generator = new (TC.Context)
-      if (auto np = dyn_cast_or_null<NamedPattern>(S->getPattern()))
+        VarDecl(/*static*/ false, /*IsLet*/ false, S->getInLoc(),
-        name = np->getBoundName().str();
+                TC.Context.getIdentifier("$generator"), generatorTy, DC);
-      generator = new (TC.Context) VarDecl(/*static*/ false, /*IsLet*/ false,
-                                           S->getInLoc(),
-                                           TC.Context.getIdentifier(name),
-                                           generatorTy, DC);
       generator->setImplicit();
       
       // Create a pattern binding to initialize the generator.

test/DebugInfo/iteration.swift

@@ -1,8 +1,9 @@
 // RUN: %swift -target x86_64-apple-macosx10.9 %s -emit-ir -g -o - | FileCheck %s
 var puzzleInput = "great minds think alike"
 var puzzleOutput = ""
+// CHECK: [ DW_TAG_auto_variable ] [$generator] [line [[@LINE+2]]]
+// CHECK: [ DW_TAG_auto_variable ] [letter] [line [[@LINE+1]]]
 for letter in puzzleInput {
-  // CHECK: [ DW_TAG_auto_variable ] [letter] [line [[@LINE-1]]]
     switch letter {
         case "a", "e", "i", "o", "u", " ":
             continue
@@ -11,3 +12,13 @@ for letter in puzzleInput {
     }
 }
 println(puzzleOutput)
+
+
+func count() {
+  // CHECK: [ DW_TAG_auto_variable ] [$generator] [line [[@LINE+2]]]
+  // CHECK: [ DW_TAG_auto_variable ] [i] [line [[@LINE+1]]]
+  for i in 0...100 {
+    println(i)
+  }
+}
+count()