Emit debug info for generic type aliases.

Before comparing the potential sugared type for equality is needs to be mapped
into the context to resolve generic type parameters to primary archetypes.

<rdar://problem/59238327>

Author: adrian-prantl

lib/IRGen/DebugTypeInfo.cpp

@@ -60,20 +60,25 @@ DebugTypeInfo DebugTypeInfo::getFromTypeInfo(swift::Type Ty,
 
 DebugTypeInfo DebugTypeInfo::getLocalVariable(VarDecl *Decl, swift::Type Ty,
                                               const TypeInfo &Info) {
-
-  auto DeclType = Decl->getInterfaceType();
-  auto RealType = Ty;
-
-  // DynamicSelfType is also sugar as far as debug info is concerned.
-  auto Sugared = DeclType;
-  if (auto DynSelfTy = DeclType->getAs<DynamicSelfType>())
-    Sugared = DynSelfTy->getSelfType();
-
   // Prefer the original, potentially sugared version of the type if
   // the type hasn't been mucked with by an optimization pass.
-  auto *Type = Sugared->isEqual(RealType) ? DeclType.getPointer()
-                                          : RealType.getPointer();
-  return getFromTypeInfo(Type, Info);
+  swift::Type DeclType = Decl->getInterfaceType();
+  swift::Type RealType = Ty;
+
+  swift::Type DebugType;
+  if (auto DynSelfTy = DeclType->getAs<DynamicSelfType>()) {
+    // DynamicSelfType is also sugar as far as debug info is concerned.
+    auto DesugaredSelf = DynSelfTy->getSelfType();
+    DebugType = DesugaredSelf->isEqual(RealType) ? DynSelfTy : RealType;
+  } else {
+    // Map the sugared type into the context to resolve bound generics and
+    // generic type aliases.
+    DeclContext *DeclCtx = Decl->getDeclContext();
+    swift::Type Sugared =
+        DeclCtx ? DeclCtx->mapTypeIntoContext(DeclType) : DeclType;
+    DebugType = Sugared->isEqual(RealType) ? Sugared : RealType;
+  }
+  return getFromTypeInfo(DebugType, Info);
 }
 
 DebugTypeInfo DebugTypeInfo::getMetadata(swift::Type Ty, llvm::Type *StorageTy,

lib/IRGen/IRGenSIL.cpp

@@ -3660,7 +3660,7 @@ void IRGenSILFunction::visitDebugValueInst(DebugValueInst *i) {
   llvm::SmallVector<llvm::Value *, 8> Copy;
   emitShadowCopyIfNeeded(SILVal, i->getDebugScope(), *VarInfo, IsAnonymous,
                          Copy);
-  bindArchetypes(DbgTy.getType());
+  bindArchetypes(RealTy);
   if (!IGM.DebugInfo)
     return;
 
@@ -3691,7 +3691,7 @@ void IRGenSILFunction::visitDebugValueAddrInst(DebugValueAddrInst *i) {
 
   auto DbgTy = DebugTypeInfo::getLocalVariable(
       Decl, RealType, getTypeInfo(SILVal->getType()));
-  bindArchetypes(DbgTy.getType());
+  bindArchetypes(RealType);
   if (!IGM.DebugInfo)
     return;
 
@@ -3991,7 +3991,7 @@ void IRGenSILFunction::emitDebugInfoForAllocStack(AllocStackInst *i,
   auto RealType = SILTy.getASTType();
   auto DbgTy = DebugTypeInfo::getLocalVariable(Decl, RealType, type);
 
-  bindArchetypes(DbgTy.getType());
+  bindArchetypes(RealType);
   if (IGM.DebugInfo)
     emitDebugVariableDeclaration(addr, DbgTy, SILTy, DS, Decl, *VarInfo,
                                  Indirection);

test/DebugInfo/bound-generic-struct-extension.swift

@@ -0,0 +1,28 @@
+// RUN: %target-swift-frontend %s -emit-ir -g -o - | %FileCheck %s
+
+// Test that a bound generic type is fully resolved in the debug info.
+
+public protocol P {}
+
+public struct S : P {
+  var x: Int
+}
+// This is significant, it must be bound to S:                    main.BoundGeneric<main.S>
+// CHECK-DAG: ![[S:[0-9]+]] = !DICompositeType({{.*}}identifier: "$s4main12BoundGenericVyAA1SVGD")
+
+public extension BoundGeneric where T == S {
+  func f() {
+// CHECK-DAG: !DILocalVariable(name: "self", arg: 1,{{.*}} line: [[@LINE-1]],{{.*}} type: ![[C_BGS:[0-9]+]],
+// CHECK-DAG: ![[C_BGS]] = !DIDerivedType(tag: DW_TAG_const_type,{{.*}} baseType: ![[BGS:[0-9]+]])
+// CHECK-DAG: ![[BGS]] = !DICompositeType(tag: DW_TAG_structure_type,{{.*}} elements: ![[ELTS:[0-9]+]],
+// CHECK-DAG: ![[ELTS]] = !{![[MEMBER:[0-9]+]]}
+// CHECK-DAG: ![[MEMBER]] = !DIDerivedType(tag: DW_TAG_member,{{.*}} baseType: ![[S]],
+  }
+}
+
+public struct BoundGeneric<T> where T : P {
+  let x : T
+}
+
+public let pat = BoundGeneric<S>(x: S(x: 23))
+pat.f()

test/DebugInfo/generic-typealias.swift

@@ -0,0 +1,19 @@
+// RUN: %target-swift-frontend %s -emit-ir -g -o - | %FileCheck %s
+
+// Test that a generic type alias is represented in the debug info.
+
+public struct S<T> {
+  public typealias Alias = (T, T)
+  // CHECK: ![[T_T:[0-9]+]] = !DICompositeType(tag: DW_TAG_structure_type, name: "$sx_xtD"
+  public let member : Alias
+  public func f(t : Alias) -> Alias { return t }
+  // CHECK: !DILocalVariable(name: "t", arg: 1,{{.*}} line: [[@LINE-1]],
+  // CHECK-SAME:             type: ![[C_ALIAS:[0-9]+]])
+  // CHECK: ![[C_ALIAS]] = !DIDerivedType(tag: DW_TAG_const_type,
+  // CHECK-SAME:                          baseType: ![[ALIAS:[0-9]+]])
+  // CHECK: ![[ALIAS]] = !DIDerivedType(tag: DW_TAG_typedef, name: "$
+  // CHECK-SAME:                        baseType: ![[T_T]])
+
+}
+
+public let s = S<Int>(member: (4, 2))