ASTMangler: Fix mangling of SILFunctionType with @pack conventions

Fixes rdar://problem/107151125.

Author: slavapestov

lib/AST/ASTMangler.cpp

@@ -1097,9 +1097,9 @@ static char getParamConvention(ParameterConvention conv) {
     case ParameterConvention::Direct_Owned: return 'x';
     case ParameterConvention::Direct_Unowned: return 'y';
     case ParameterConvention::Direct_Guaranteed: return 'g';
-    case ParameterConvention::Pack_Owned: return 'x';
-    case ParameterConvention::Pack_Inout: return 'y';
-    case ParameterConvention::Pack_Guaranteed: return 'g';
+    case ParameterConvention::Pack_Owned: return 'v';
+    case ParameterConvention::Pack_Inout: return 'm';
+    case ParameterConvention::Pack_Guaranteed: return 'p';
   }
   llvm_unreachable("bad parameter convention");
 }

lib/Demangling/Demangler.cpp

@@ -2068,7 +2068,7 @@ NodePointer Demangler::demangleImplParamConvention(Node::Kind ConvKind) {
     case 'y': attr = "@unowned"; break;
     case 'v': attr = "@pack_owned"; break;
     case 'p': attr = "@pack_guaranteed"; break;
-    case 'm': attr = "@pack_guaranteed"; break;
+    case 'm': attr = "@pack_inout"; break;
     default:
       pushBack();
       return nullptr;

test/DebugInfo/variadic-generics-closure.swift

@@ -0,0 +1,4 @@
+// RUN: %target-swift-frontend -emit-ir %s -g | %FileCheck %s
+
+// CHECK: !{{[0-9]+}} = !DICompositeType(tag: DW_TAG_structure_type, name: "$sxxQp_QSiIgp_D", {{.*}})
+public func f<each Input>(builder: (repeat each Input) -> ()) {}