AST: Clean up ExistentialLayout construction

Author: slavapestov

include/swift/AST/Requirement.h

@@ -261,21 +261,6 @@ struct InverseRequirement {
   static void expandDefaults(ASTContext &ctx,
                              ArrayRef<Type> gps,
                              SmallVectorImpl<StructuralRequirement> &result);
-
-  /// Adds the inferred default protocols for an assumed generic parameter with
-  /// respect to that parameter's inverses and existing required protocols.
-  /// For example, if an inverse ~P exists, then P will not be added to the
-  /// protocols list.
-  ///
-  /// Similarly, if the protocols list has a protocol Q that already implies
-  /// Copyable, then we will not add `Copyable` to the protocols list.
-  ///
-  /// \param inverses the inverses '& ~P' that are applied to the generic param.
-  /// \param protocols the existing required protocols, to which defaults will
-  ///                  be appended.
-  static void expandDefaults(ASTContext &ctx,
-                             InvertibleProtocolSet inverses,
-                             SmallVectorImpl<ProtocolDecl*> &protocols);
 };
 
 } // end namespace swift

lib/AST/Requirement.cpp

@@ -350,59 +350,12 @@ void InverseRequirement::expandDefaults(
       !ctx.LangOpts.hasFeature(Feature::NoncopyableGenerics))
     return;
 
-  SmallVector<ProtocolDecl*, NumInvertibleProtocols> defaults;
-  expandDefaults(ctx, /*inverses=*/{}, defaults);
-
-  // Fast-path.
-  if (defaults.empty())
-    return;
-
   for (auto gp : gps) {
-    for (auto *proto : defaults) {
-      auto protoTy = proto->getDeclaredInterfaceType();
-      result.push_back({{RequirementKind::Conformance, gp, protoTy},
-                        SourceLoc()});
+    for (auto ip : InvertibleProtocolSet::full()) {
+      auto proto = ctx.getProtocol(getKnownProtocolKind(ip));
+      result.push_back({{RequirementKind::Conformance, gp,
+                         proto->getDeclaredInterfaceType()},
+                         SourceLoc()});
     }
   }
-}
-
-void InverseRequirement::expandDefaults(
-    ASTContext &ctx,
-    InvertibleProtocolSet inverses,
-    SmallVectorImpl<ProtocolDecl*> &protocols) {
-
-  // Skip unless noncopyable generics is enabled
-  if (!ctx.LangOpts.hasFeature(swift::Feature::NoncopyableGenerics))
-    return;
-
-  // Try to add all invertible protocols, unless:
-  //  - an inverse was provided
-  //  - an existing protocol already requires it
-  for (auto ip : InvertibleProtocolSet::full()) {
-    // This matches with `lookupExistentialConformance`'s use of 'inheritsFrom'.
-    bool alreadyRequired = false;
-    for (auto proto : protocols) {
-      if (proto->isSpecificProtocol(getKnownProtocolKind(ip))
-          || proto->requiresInvertible(ip)) {
-        alreadyRequired = true;
-        break;
-      }
-    }
-
-    // If some protocol member already implies P, then we don't need to
-    // add a requirement for P.
-    if (alreadyRequired) {
-      assert(!inverses.contains(ip) && "cannot require P and ~P");
-      continue;
-    }
-
-    // Nothing implies P, so unless there's an inverse ~P, add the requirement.
-    if (inverses.contains(ip))
-      continue;
-
-    auto proto = ctx.getProtocol(getKnownProtocolKind(ip));
-    assert(proto && "missing Copyable/Escapable from stdlib!");
-
-    protocols.push_back(proto);
-  }
-}
+}

lib/AST/Type.cpp

@@ -278,7 +278,20 @@ bool TypeBase::allowsOwnership(const GenericSignatureImpl *sig) {
   return getCanonicalType().allowsOwnership(sig);
 }
 
+static void expandDefaults(SmallVectorImpl<ProtocolDecl *> &protocols,
+                           InvertibleProtocolSet inverses,
+                           ASTContext &ctx) {
+  if (ctx.LangOpts.hasFeature(Feature::NoncopyableGenerics)) {
+    for (auto ip : InvertibleProtocolSet::full()) {
+      if (!inverses.contains(ip)) {
+        auto *proto = ctx.getProtocol(getKnownProtocolKind(ip));
+        protocols.push_back(proto);
+      }
+    }
+  }
 
+  ProtocolType::canonicalizeProtocols(protocols);
+}
 
 ExistentialLayout::ExistentialLayout(CanProtocolType type) {
   auto *protoDecl = type->getDecl();
@@ -291,9 +304,7 @@ ExistentialLayout::ExistentialLayout(CanProtocolType type) {
   representsAnyObject = false;
 
   protocols.push_back(protoDecl);
-
-  // NOTE: all the invertible protocols are usable from ObjC.
-  InverseRequirement::expandDefaults(type->getASTContext(), {}, protocols);
+  expandDefaults(protocols, InvertibleProtocolSet(), type->getASTContext());
 }
 
 ExistentialLayout::ExistentialLayout(CanProtocolCompositionType type) {
@@ -326,13 +337,26 @@ ExistentialLayout::ExistentialLayout(CanProtocolCompositionType type) {
     protocols.push_back(protoDecl);
   }
 
-  representsAnyObject =
-      hasExplicitAnyObject && !explicitSuperclass && getProtocols().empty();
+  auto inverses = type->getInverses();
+  expandDefaults(protocols, inverses, type->getASTContext());
+
+  representsAnyObject = [&]() {
+    if (!hasExplicitAnyObject)
+      return false;
+
+    if (explicitSuperclass)
+      return false;
 
-  // NOTE: all the invertible protocols are usable from ObjC.
-  InverseRequirement::expandDefaults(type->getASTContext(),
-                                     type->getInverses(),
-                                     protocols);
+    if (!inverses.empty())
+      return false;
+
+    for (auto *proto : protocols) {
+      if (!proto->getInvertibleProtocolKind())
+        return false;
+    }
+
+    return true;
+  }();
 }
 
 ExistentialLayout::ExistentialLayout(CanParameterizedProtocolType type)
@@ -1503,6 +1527,10 @@ static void addProtocols(Type T,
 
 static void canonicalizeProtocols(SmallVectorImpl<ProtocolDecl *> &protocols,
                                   ParameterizedProtocolMap *parameterized) {
+  // Skip a bunch of useless work.
+  if (protocols.size() <= 1)
+    return;
+
   llvm::SmallDenseMap<ProtocolDecl *, unsigned> known;
   bool zappedAny = false;
 

test/SILOptimizer/dead_witness_module.swift

@@ -1,5 +1,5 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swift-frontend -Onone -parse-stdlib -parse-as-library  -module-name TestModule  %S/Inputs/TestModule.swift -emit-module-path %t/TestModule.swiftmodule 
+// RUN: %target-swift-frontend -Onone -parse-as-library  -module-name TestModule  %S/Inputs/TestModule.swift -emit-module-path %t/TestModule.swiftmodule 
 // RUN: %target-swift-frontend -O %s -I %t -emit-sil | %FileCheck %s
 
 // DeadFunctionElimination may not remove a method from a witness table which