Revert "[ConstraintSystem] Adjust the way pack parameters are opened"

This reverts commit 2227930.

Author: xedin

lib/Sema/ConstraintSystem.cpp

@@ -855,21 +855,7 @@ Type ConstraintSystem::openUnboundGenericType(GenericTypeDecl *decl,
     result = DC->mapTypeIntoContext(result);
   }
 
-  return result.transform([&](Type type) -> Type {
-    // Although generic parameters are declared with just `each`
-    // their interface types introduce a pack expansion which
-    // means that the solver has to extact generic argument type
-    // variable from Pack{repeat ...} and drop that structure to
-    // make sure that generic argument gets inferred to a pack type.
-    if (auto *packTy = type->getAs<PackType>()) {
-      assert(packTy->getNumElements() == 1);
-      auto *expansion = packTy->getElementType(0)->castTo<PackExpansionType>();
-      auto *typeVar = expansion->getPatternType()->castTo<TypeVariableType>();
-      assert(typeVar->getImpl().getGenericParameter() &&
-             typeVar->getImpl().canBindToPack());
-      return typeVar;
-    }
-
+  return result.transform([&](Type type) {
     if (auto *expansion = dyn_cast<PackExpansionType>(type.getPointer()))
       return openPackExpansionType(expansion, replacements, locator);
     return type;
@@ -1022,15 +1008,6 @@ Type ConstraintSystem::openType(Type type, OpenedTypeMap &replacements,
         }
       }
 
-      // While opening variadic generic types that appear in other types
-      // we need to extract generic parameter from Pack{repeat ...} structure
-      // that gets introduced by the interface type, see
-      // \c openUnboundGenericType for more details.
-      if (auto *packTy = type->getAs<PackType>()) {
-        if (auto expansion = packTy->unwrapSingletonPackExpansion())
-          type = expansion->getPatternType();
-      }
-
       if (auto *expansion = type->getAs<PackExpansionType>()) {
         return openPackExpansionType(expansion, replacements, locator);
       }

test/Constraints/variadic_generic_types.swift

@@ -29,30 +29,3 @@ struct MissingMemberError<each T> {
     // expected-error@-1 {{value of type 'MissingMemberError<repeat each T>' has no member 'doesNotExist'}}
   }
 }
-
-// https://github.com/apple/swift/issues/66095
-do {
-  struct Test<each S> {
-    init(_ s: repeat each S) {}
-  }
-
-  func test1<each T>(_ v: repeat each T) -> Test<repeat each T> {
-    return Test(repeat each v) // Ok
-  }
-
-  func test2<each T>(_ v: repeat each T) -> Test<repeat each T> {
-    return Test<repeat each T>(repeat each v) // Ok
-  }
-
-  func test3<each T>(_ v: repeat each T) -> Test<String, repeat each T, Int> {
-    return Test("a", repeat each v, 42) // Ok
-  }
-
-  func test4<each T>(_ v: repeat each T) -> Test<repeat each T, String, Int> {
-    return Test<repeat each T, String, Int>(repeat each v, "a", 42) // Ok
-  }
-
-  func test5<each T>(_ v: repeat each T) -> Test<String, Int, repeat each T> {
-    return Test<String, Int, repeat each T>("a", 42, repeat each v) // Ok
-  }
-}