SIL: Thunks that capture local environments must also capture the primary environment

I suspect there are latent bugs here with generic-class-constrained existentials,
same-element requirements involving packs, etc. We can't assume that the
local archetypes don't have "hidden" dependencies on the outer parameters
that are not encoded in the thunk's interface type.

Author: slavapestov

lib/SIL/IR/SILFunctionType.cpp

@@ -3021,43 +3021,39 @@ struct LocalArchetypeRequirementCollector {
 ///
 /// \param localArchetypes - the list of local archetypes to promote
 ///   into the signature, if any
-/// \param inheritGenericSig - whether to inherit the generic signature from the
-/// parent function.
 /// \param genericEnv - the new generic environment
 /// \param contextSubs - map non-local archetypes from the original function
 ///    to archetypes in the thunk
 /// \param interfaceSubs - map interface types to old archetypes
 static CanGenericSignature
 buildThunkSignature(SILFunction *fn,
-                    bool inheritGenericSig,
                     ArrayRef<CanLocalArchetypeType> localArchetypes,
                     GenericEnvironment *&genericEnv,
                     SubstitutionMap &contextSubs,
                     SubstitutionMap &interfaceSubs,
                     llvm::DenseMap<ArchetypeType*, Type> &contextLocalArchetypes) {
   auto *mod = fn->getModule().getSwiftModule();
   auto &ctx = mod->getASTContext();
+  auto forwardingSubs = fn->getForwardingSubstitutionMap();
 
   // If there are no local archetypes, we just inherit the generic
   // environment from the parent function.
   if (localArchetypes.empty()) {
     auto genericSig =
       fn->getLoweredFunctionType()->getInvocationGenericSignature();
     genericEnv = fn->getGenericEnvironment();
-    interfaceSubs = fn->getForwardingSubstitutionMap();
+    interfaceSubs = forwardingSubs;
     contextSubs = interfaceSubs;
     return genericSig;
   }
 
   // Add the existing generic signature.
   unsigned depth = 0;
   GenericSignature baseGenericSig;
-  if (inheritGenericSig) {
-    if (auto genericSig =
-          fn->getLoweredFunctionType()->getInvocationGenericSignature()) {
-      baseGenericSig = genericSig;
-      depth = genericSig.getGenericParams().back()->getDepth() + 1;
-    }
+  if (auto genericSig =
+        fn->getLoweredFunctionType()->getInvocationGenericSignature()) {
+    baseGenericSig = genericSig;
+    depth = genericSig.getGenericParams().back()->getDepth() + 1;
   }
 
   // Add new generic parameters to replace the local archetypes.
@@ -3088,13 +3084,11 @@ buildThunkSignature(SILFunction *fn,
           ->getInvocationGenericSignature()) {
     contextSubs = SubstitutionMap::get(
       calleeGenericSig,
-      [&](SubstitutableType *type) -> Type {
-        return genericEnv->mapTypeIntoContext(type);
-      },
-      MakeAbstractConformanceForGenericType());
+      genericEnv->getForwardingSubstitutionMap());
   }
 
   // Calculate substitutions to map interface types to the caller's archetypes.
+
   interfaceSubs = SubstitutionMap::get(
     genericSig,
     [&](SubstitutableType *type) -> Type {
@@ -3103,7 +3097,7 @@ buildThunkSignature(SILFunction *fn,
           return collector.ParamSubs[param->getIndex()];
         }
       }
-      return fn->mapTypeIntoContext(type);
+      return Type(type).subst(forwardingSubs);
     },
     MakeAbstractConformanceForGenericType());
 
@@ -3142,18 +3136,14 @@ CanSILFunctionType swift::buildSILFunctionThunkType(
   if (withoutActuallyEscaping)
     extInfoBuilder = extInfoBuilder.withNoEscape(false);
 
-  // Does the thunk type involve archetypes other than local archetypes?
-  bool hasArchetypes = false;
   // Does the thunk type involve a local archetype type?
   SmallVector<CanLocalArchetypeType, 8> localArchetypes;
   auto archetypeVisitor = [&](CanType t) {
     if (auto archetypeTy = dyn_cast<ArchetypeType>(t)) {
-      if (auto opened = dyn_cast<LocalArchetypeType>(archetypeTy)) {
-        auto root = opened.getRoot();
+      if (auto local = dyn_cast<LocalArchetypeType>(archetypeTy)) {
+        auto root = local.getRoot();
         if (llvm::find(localArchetypes, root) == localArchetypes.end())
           localArchetypes.push_back(root);
-      } else {
-        hasArchetypes = true;
       }
     }
   };
@@ -3169,7 +3159,6 @@ CanSILFunctionType swift::buildSILFunctionThunkType(
     sourceType.visit(archetypeVisitor);
 
     genericSig = buildThunkSignature(fn,
-                                     hasArchetypes,
                                      localArchetypes,
                                      genericEnv,
                                      contextSubs,

test/SILGen/partial_apply_protocol.swift

@@ -54,8 +54,6 @@ func testClonable(c: Clonable) {
 
 //===----------------------------------------------------------------------===//
 // Partial apply of methods returning Self-derived types from generic context
-//
-// Make sure the thunk only has the context generic parameters if needed!
 //===----------------------------------------------------------------------===//
 
 // CHECK-LABEL: sil hidden [ossa] @$s22partial_apply_protocol28testClonableInGenericContext1c1tyAA0E0_p_xtlF : $@convention(thin) <T> (@in_guaranteed any Clonable, @in_guaranteed T) -> ()
@@ -75,8 +73,8 @@ func testClonableInGenericContext<T>(c: Clonable, t: T) {
   // CHECK: [[METHOD_FN:%.*]] = witness_method $@opened("{{.*}}", any Clonable) Self, #Clonable.getCloneFn :
   // CHECK: [[RESULT:%.*]] = apply [[METHOD_FN]]<@opened("{{.*}}", any Clonable) Self>({{.*}})
   // CHECK: [[RESULT_CONV:%.*]] = convert_function [[RESULT]]
-  // CHECK: [[THUNK_FN:%.*]] = function_ref @$sxIegr_22partial_apply_protocol8Clonable_pIegr_AaBRzlTR : $@convention(thin) <τ_0_0 where τ_0_0 : Clonable> (@guaranteed @callee_guaranteed () -> @out τ_0_0) -> @out any Clonable
-  // CHECK: [[THUNK:%.*]] = partial_apply [callee_guaranteed] [[THUNK_FN]]<@opened("{{.*}}", any Clonable) Self>([[RESULT_CONV]]) : $@convention(thin) <τ_0_0 where τ_0_0 : Clonable> (@guaranteed @callee_guaranteed () -> @out τ_0_0) -> @out any Clonable
+  // CHECK: [[THUNK_FN:%.*]] = function_ref @$sqd__Iegr_22partial_apply_protocol8Clonable_pIegr_AaBRd__r__lTR : $@convention(thin) <τ_0_0><τ_1_0 where τ_1_0 : Clonable> (@guaranteed @callee_guaranteed () -> @out τ_1_0) -> @out any Clonable
+  // CHECK: [[THUNK:%.*]] = partial_apply [callee_guaranteed] [[THUNK_FN]]<T, @opened("{{.*}}", any Clonable) Self>([[RESULT_CONV]]) : $@convention(thin) <τ_0_0><τ_1_0 where τ_1_0 : Clonable> (@guaranteed @callee_guaranteed () -> @out τ_1_0) -> @out any Clonable
   let _: () -> Clonable = c.getCloneFn()
 
   // CHECK: [[THUNK_FN:%.*]] = function_ref @$s22partial_apply_protocol28testClonableInGenericContext1c1tyAA0E0_p_xtlFAaE_pycycAaE_pcfu5_ : $@convention(thin) (@in_guaranteed any Clonable) -> @owned @callee_guaranteed () -> @owned @callee_guaranteed () -> @out any Clonable

test/SILGen/variadic-generic-reabstract-tuple-result.swift

@@ -312,7 +312,7 @@ func test11<each T>() -> Use<repeat each T> {
 // CHECK-NEXT:    [[DEST_ELT_ADDR:%.*]] = pack_element_get [[EXPANSION_INDEX]] of %0 : $*Pack{repeat @callee_guaranteed @substituted <τ_0_0> (@in_guaranteed τ_0_0) -> Bool for <each T>} as $*@callee_guaranteed @substituted <τ_0_0> (@in_guaranteed τ_0_0) -> Bool for <@pack_element([[UUID]]) each T>
 // CHECK-NEXT:    [[ESCAPING_ELT:%.*]] = convert_function [[ELT]]
 // CHECK-NEXT:    // function_ref
-// CHECK-NEXT:    [[THUNK:%.*]] = function_ref @$sxSbIegnr_xSbIegnd_lTR : $@convention(thin) <τ_0_0> (@in_guaranteed τ_0_0, @guaranteed @callee_guaranteed (@in_guaranteed τ_0_0) -> @out Bool) -> Bool
+// CHECK-NEXT:    [[THUNK:%.*]] = function_ref @$sqd__SbIegnr_qd__SbIegnd_Rvzr__lTR : $@convention(thin) <each τ_0_0><τ_1_0> (@in_guaranteed τ_1_0, @guaranteed @callee_guaranteed (@in_guaranteed τ_1_0) -> @out Bool) -> Bool
 // CHECK-NEXT:    [[CONVERTED_ELT:%.*]] = partial_apply
 // CHECK-NEXT:    [[CONVERTED_ELT_2:%.*]] = convert_function [[CONVERTED_ELT]]
 // CHECK-NEXT:    store [[CONVERTED_ELT_2]] to [init] [[DEST_ELT_ADDR]] :

test/SILGen/variadic-generic-reabstraction.swift

@@ -27,8 +27,8 @@ func forwardAndReabstractFunctionPack<each T>(functions: repeat (each T) -> Bool
 // CHECK-NEXT:    [[COPY_CONVERT:%.*]] = convert_function [[COPY]] : $@noescape @callee_guaranteed @substituted <τ_0_0> (@in_guaranteed τ_0_0) -> Bool for <@pack_element([[UUID]]) each T> to $@noescape @callee_guaranteed (@in_guaranteed @pack_element([[UUID]]) each T) -> Bool
 //   Wrap in the conversion thunk.
 // CHECK-NEXT:    // function_ref
-// CHECK-NEXT:    [[THUNK:%.*]] = function_ref @$sxSbIgnd_xSbIegnr_lTR : $@convention(thin) <τ_0_0> (@in_guaranteed τ_0_0, @guaranteed @noescape @callee_guaranteed (@in_guaranteed τ_0_0) -> Bool) -> @out Bool
-// CHECK-NEXT:    [[THUNKED:%.*]] = partial_apply [callee_guaranteed] [[THUNK]]<@pack_element([[UUID]]) each T>([[COPY_CONVERT]])
+// CHECK-NEXT:    [[THUNK:%.*]] = function_ref @$sqd__SbIgnd_qd__SbIegnr_Rvzr__lTR : $@convention(thin) <each τ_0_0><τ_1_0> (@in_guaranteed τ_1_0, @guaranteed @noescape @callee_guaranteed (@in_guaranteed τ_1_0) -> Bool) -> @out Bool
+// CHECK-NEXT:    [[THUNKED:%.*]] = partial_apply [callee_guaranteed] [[THUNK]]<Pack{repeat each T}, @pack_element([[UUID]]) each T>([[COPY_CONVERT]])
 //   Convert to a substituted type.
 // CHECK-NEXT:    [[THUNKED_CONVERT:%.*]] = convert_function [[THUNKED]] : $@callee_guaranteed (@in_guaranteed @pack_element([[UUID]]) each T) -> @out Bool to $@callee_guaranteed @substituted <τ_0_0, τ_0_1> (@in_guaranteed τ_0_0) -> @out τ_0_1 for <@pack_element([[UUID]]) each T, Bool>
 //   Convert to noescape.