AST: Remove Substitution::subst()

I want to get rid of Substitution entirely, and now we have
the right abstractions to do everything with SubstitutionMap.

Author: slavapestov

include/swift/AST/Substitution.h

@@ -54,15 +54,6 @@ class Substitution {
              const PrintOptions &PO = PrintOptions()) const;
   void dump() const;
   void dump(llvm::raw_ostream &os, unsigned indent = 0) const;
-  
-  /// Apply a substitution to this substitution's replacement type and
-  /// conformances.
-  Substitution subst(const SubstitutionMap &subMap) const;
-  Substitution subst(TypeSubstitutionFn subs,
-                     LookupConformanceFn conformances) const;
-
-private:
-  friend class ProtocolConformance;
 };
 
 } // end namespace swift

include/swift/AST/SubstitutionMap.h

@@ -87,6 +87,10 @@ class SubstitutionMap {
   /// Query whether any replacement types in the map contain archetypes.
   bool hasArchetypes() const;
 
+  /// Query whether any replacement types in the map contain an opened
+  /// existential.
+  bool hasOpenedExistential() const;
+
   /// Query whether any replacement type sin the map contain dynamic Self.
   bool hasDynamicSelf() const;
 

lib/AST/Substitution.cpp

@@ -42,44 +42,3 @@ Substitution::Substitution(Type Replacement,
   assert(Replacement->isMaterializable()
          && "cannot substitute with a non-materializable type");
 }
-
-Substitution Substitution::subst(const SubstitutionMap &subMap) const {
-  return subst(QuerySubstitutionMap{subMap},
-               LookUpConformanceInSubstitutionMap(subMap));
-}
-
-Substitution Substitution::subst(TypeSubstitutionFn subs,
-                                 LookupConformanceFn conformances) const {
-  // Substitute the replacement.
-  Type substReplacement = Replacement.subst(subs, conformances,
-                                            SubstFlags::UseErrorType);
-  assert(!substReplacement->hasError() &&
-         "substitution replacement failed");
-
-  if (substReplacement->isEqual(Replacement))
-    return *this;
-
-  if (Conformance.empty()) {
-    return {substReplacement, Conformance};
-  }
-
-  bool conformancesChanged = false;
-  SmallVector<ProtocolConformanceRef, 4> substConformances;
-  substConformances.reserve(Conformance.size());
-
-  for (auto c : Conformance) {
-    auto newC = c.subst(Replacement, subs, conformances);
-    if (c != newC)
-      conformancesChanged = true;
-    substConformances.push_back(newC);
-  }
-  assert(substConformances.size() == Conformance.size());
-
-  ArrayRef<ProtocolConformanceRef> substConfs;
-  if (conformancesChanged)
-    substConfs = Replacement->getASTContext().AllocateCopy(substConformances);
-  else
-    substConfs = Conformance;
-
-  return Substitution{substReplacement, substConfs};
-}

lib/AST/SubstitutionMap.cpp

@@ -38,6 +38,13 @@ bool SubstitutionMap::hasArchetypes() const {
   return false;
 }
 
+bool SubstitutionMap::hasOpenedExistential() const {
+  for (auto &entry : subMap)
+    if (entry.second->hasOpenedExistential())
+      return true;
+  return false;
+}
+
 bool SubstitutionMap::hasDynamicSelf() const {
   for (auto &entry : subMap)
     if (entry.second->hasDynamicSelfType())

lib/AST/Type.cpp

@@ -2905,17 +2905,20 @@ static Type substType(Type derivedType,
       if (boxTy->getGenericArgs().empty())
         return Type(boxTy);
 
-      SmallVector<Substitution, 4> substArgs;
-      for (auto &arg : boxTy->getGenericArgs()) {
-        substArgs.push_back(arg.subst(substitutions, lookupConformances));
-      }
-      for (auto &arg : substArgs) {
+      auto subMap = boxTy->getLayout()->getGenericSignature()
+        ->getSubstitutionMap(boxTy->getGenericArgs());
+      subMap = subMap.subst(substitutions, lookupConformances);
+
+      SmallVector<Substitution, 4> newSubs;
+      boxTy->getLayout()->getGenericSignature()
+        ->getSubstitutions(subMap, newSubs);
+      for (auto &arg : newSubs) {
         arg = Substitution(arg.getReplacement()->getCanonicalType(),
                            arg.getConformances());
       }
       return SILBoxType::get(boxTy->getASTContext(),
                              boxTy->getLayout(),
-                             substArgs);
+                             newSubs);
     }
 
     // We only substitute for substitutable types and dependent member types.

lib/SILGen/SILGenBridging.cpp

@@ -79,8 +79,12 @@ emitBridgeNativeToObjectiveC(SILGenFunction &gen,
     GenericEnvironment *witnessEnv = witness.getSyntheticEnvironment();
     SubstitutionMap typeSubMap = witnessEnv
       ->getSubstitutionMap(typeSubstitutions);
-    for (auto sub : witnessSubstitutions) {
-      substitutionsBuf.push_back(sub.subst(typeSubMap));
+    SubstitutionMap witnessSubMap;
+    if (auto *genericSig = cast<FuncDecl>(witness.getDecl())
+          ->getGenericSignature()) {
+      witnessSubMap = genericSig->getSubstitutionMap(witnessSubstitutions);
+      witnessSubMap = witnessSubMap.subst(typeSubMap);
+      genericSig->getSubstitutions(witnessSubMap, substitutionsBuf);
     }
     substitutions = substitutionsBuf;
   }

lib/SILOptimizer/Transforms/PerformanceInliner.cpp

@@ -199,15 +199,14 @@ static bool calleeHasPartialApplyWithOpenedExistentials(FullApplySite AI) {
         auto PAISubs = PAI->getSubstitutions();
         if (PAISubs.empty())
           continue;
+
         // Check if any of substitutions would contain open existentials
         // after inlining.
-        for (auto PAISub : PAISubs) {
-          if (!PAISub.getReplacement()->hasArchetype())
-            continue;
-          auto NewPAISub = PAISub.subst(SubsMap);
-          if (NewPAISub.getReplacement()->hasOpenedExistential())
-            return true;
-        }
+        auto PAISubMap = PAI->getOrigCalleeType()
+          ->getGenericSignature()->getSubstitutionMap(PAISubs);
+        PAISubMap = PAISubMap.subst(SubsMap);
+        if (PAISubMap.hasOpenedExistential())
+          return true;
       }
     }
   }
@@ -405,11 +404,12 @@ bool SILPerformanceInliner::isProfitableToInline(FullApplySite AI,
 
         // Create the list of substitutions as they will be after
         // inlining.
+        auto Sig = FAI.getOrigCalleeType()->getGenericSignature();
+        auto SubMap = Sig->getSubstitutionMap(Subs);
+        SubMap = SubMap.subst(CalleeSubstMap);
+
         SmallVector<Substitution, 4> NewSubs;
-        for (auto Sub : Subs) {
-          auto NewSub = Sub.subst(CalleeSubstMap);
-          NewSubs.push_back(NewSub);
-        }
+        Sig->getSubstitutions(SubMap, NewSubs);
 
         // Check if the call can be devirtualized.
         if (isa<ClassMethodInst>(def) || isa<WitnessMethodInst>(def) ||