[Serialization] Serialize SILBoxType substitutions directly.

include/swift/Serialization/ModuleFormat.h

@@ -54,7 +54,7 @@ const uint16_t VERSION_MAJOR = 0;
 /// in source control, you should also update the comment to briefly
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
-const uint16_t VERSION_MINOR = 301; // Last change: Deterministic conformances
+const uint16_t VERSION_MINOR = 302; // Last change: SIL box type substitutions
 
 using DeclID = PointerEmbeddedInt<unsigned, 31>;
 using DeclIDField = BCFixed<31>;
@@ -716,8 +716,8 @@ namespace decls_block {
 
   using SILBoxTypeLayout = BCRecordLayout<
     SIL_BOX_TYPE,
-    SILLayoutIDField,    // layout
-    BCArray<TypeIDField> // generic arguments
+    SILLayoutIDField     // layout
+                         // trailing substitutions
   >;
 
   template <unsigned Code>

lib/Serialization/Deserialization.cpp

@@ -3977,9 +3977,8 @@ Type ModuleFile::getType(TypeID TID) {
 
   case decls_block::SIL_BOX_TYPE: {
     SILLayoutID layoutID;
-    ArrayRef<uint64_t> args;
 
-    decls_block::SILBoxTypeLayout::readRecord(scratch, layoutID, args);
+    decls_block::SILBoxTypeLayout::readRecord(scratch, layoutID);
 
     // Get the layout.
     auto getLayout = [&]() -> SILLayout * {
@@ -4008,49 +4007,20 @@ Type ModuleFile::getType(TypeID TID) {
 
     SmallVector<Substitution, 4> genericArgs;
     if (auto sig = layout->getGenericSignature()) {
-      if (args.size() != sig->getAllDependentTypes().size()) {
-        error();
-        return nullptr;
-      }
-      TypeSubstitutionMap mappings;
-
-      for (unsigned i : indices(sig->getGenericParams())) {
-        mappings[sig->getGenericParams()[i]] =
-          getType(args[i])->getCanonicalType();
-      }
-
-      bool ok = true;
-      sig->getSubstitutions(mappings,
-        [&](CanType depTy, Type replacementTy, ProtocolType *proto)
-        -> ProtocolConformanceRef {
-          if (replacementTy->is<SubstitutableType>()
-              || replacementTy->is<DependentMemberType>())
-            return ProtocolConformanceRef(proto->getDecl());
-
-          auto conformance = getAssociatedModule()
-            ->lookupConformance(replacementTy, proto->getDecl(), nullptr);
-          if (!conformance) {
-            error();
-            ok = false;
-            return ProtocolConformanceRef(proto->getDecl());
-          }
-          return *conformance;
-        },
-        genericArgs);
-      if (!ok)
-        return nullptr;
-
-      for (auto &arg : genericArgs) {
-        arg = Substitution(arg.getReplacement()->getCanonicalType(),
-                           arg.getConformances());
-      }
-    } else {
-      if (args.size() != 0) {
-        error();
-        return nullptr;
+      for (unsigned i : range(sig->getAllDependentTypes().size())) {
+        (void)i;
+        auto sub = maybeReadSubstitution(DeclTypeCursor);
+        if (!sub) {
+          error();
+          return nullptr;
+        }
+
+        genericArgs.push_back(
+          Substitution(sub->getReplacement()->getCanonicalType(),
+                       sub->getConformances()));
       }
     }
-    
+
     typeOrOffset = SILBoxType::get(getContext(), layout, genericArgs);
     break;
   }

lib/Serialization/Serialization.cpp

@@ -3185,13 +3185,18 @@ void Serializer::writeType(Type ty) {
 
     unsigned abbrCode = DeclTypeAbbrCodes[SILBoxTypeLayout::Code];
     SILLayoutID layoutRef = addSILLayoutRef(boxTy->getLayout());
-
-    SmallVector<TypeID, 4> genericArgs;
-    for (auto &arg : boxTy->getGenericArgs())
-      genericArgs.push_back(addTypeRef(arg.getReplacement()));
-
-    SILBoxTypeLayout::emitRecord(Out, ScratchRecord, abbrCode,
-                                 layoutRef, genericArgs);
+
+#ifndef NDEBUG
+    if (auto sig = boxTy->getLayout()->getGenericSignature()) {
+      assert(sig->getAllDependentTypes().size()
+               == boxTy->getGenericArgs().size());
+    }
+#endif
+
+    SILBoxTypeLayout::emitRecord(Out, ScratchRecord, abbrCode, layoutRef);
+
+    // Write the set of substitutions.
+    writeSubstitutions(boxTy->getGenericArgs(), DeclTypeAbbrCodes);
     break;
   }
 

test/Serialization/sil_box_types.sil

@@ -24,4 +24,4 @@ sil @boxes_extra_reqs : $@convention(thin) <T where T : Q, T.AT : P> (@owned <τ
 bb0(%0 : $<τ_0_0 where τ_0_0 : Q, τ_0_0.AT : P> { var τ_0_0 } <T, T.AT>):
   %1 = project_box %0 : $<τ_0_0 where τ_0_0 : Q, τ_0_0.AT : P> { var τ_0_0 } <T, T.AT>, 0
   return undef : $()
-}
+}