[Sema] Eliminate the last use of the IterativeTypeChecker.

Implement TypeChecker::resolveInheritedProtocols() in terms of
"getInheritedType()" queries, instead.

[Sema] Put back resolveInheritedProtocols().

We're still depending on it to update state in some cases.

Author: DougGregor

include/swift/AST/LazyResolver.h

@@ -77,9 +77,6 @@ class LazyResolver {
   /// Resolve the raw type of the given enum.
   virtual Type getRawType(EnumDecl *enumDecl) = 0;
 
-  /// Resolve the inherited protocols of a given protocol.
-  virtual void resolveInheritedProtocols(ProtocolDecl *protocol) = 0;
-
   /// Get a specific inherited type from the given declaration.
   virtual Type getInheritedType(
                         llvm::PointerUnion<TypeDecl *, ExtensionDecl *> decl,

lib/AST/Decl.cpp

@@ -3280,8 +3280,8 @@ bool ProtocolDecl::requiresClassSlow() {
   //
   // FIXME: Use the requirement signature if available.
   Bits.ProtocolDecl.RequiresClass = false;
-  for (auto inherited : getInherited()) {
-    auto type = inherited.getType();
+  for (unsigned i : indices(getInherited())) {
+    Type type = getInheritedType(i);
     assert(type && "Should have type checked inheritance clause by now");
     if (type->isExistentialType()) {
       auto layout = type->getExistentialLayout();

lib/Sema/TypeCheckDecl.cpp

@@ -275,8 +275,8 @@ void TypeChecker::validateWhereClauses(ProtocolDecl *protocol,
 }
 
 void TypeChecker::resolveInheritedProtocols(ProtocolDecl *protocol) {
-  IterativeTypeChecker ITC(*this);
-  ITC.satisfy(requestInheritedProtocols(protocol));
+  for (unsigned i : indices(protocol->getInherited()))
+    (void)protocol->getInheritedType(i);
   resolveTrailingWhereClause(protocol);
 }
 

lib/Sema/TypeChecker.h

@@ -1572,7 +1572,7 @@ class TypeChecker final : public LazyResolver {
   Type getRawType(EnumDecl *enumDecl) override;
 
   /// Resolve the inherited protocols of a given protocol.
-  void resolveInheritedProtocols(ProtocolDecl *protocol) override;
+  void resolveInheritedProtocols(ProtocolDecl *protocol);
 
   /// Validate a protocol's where clause, along with the where clauses of
   /// its associated types.

test/decl/protocol/protocols.swift

@@ -102,11 +102,12 @@ protocol CircleMiddle : CircleStart { func circle_middle() } // expected-error
 // expected-error@-1{{circular protocol inheritance 'CircleMiddle' -> 'CircleStart' -> 'CircleEnd' -> 'CircleMiddle'}}
 protocol CircleStart : CircleEnd { func circle_start() }
 // expected-note@-1{{protocol 'CircleStart' declared here}}
+// expected-error@-2{{circular protocol inheritance CircleStart}}
 protocol CircleEnd : CircleMiddle { func circle_end()} // expected-note{{protocol 'CircleEnd' declared here}}
 // expected-error@-1{{circular protocol inheritance CircleEnd}}
 
 protocol CircleEntry : CircleTrivial { }
-protocol CircleTrivial : CircleTrivial { } // expected-error 3{{circular protocol inheritance CircleTrivial}}
+protocol CircleTrivial : CircleTrivial { } // expected-error 2{{circular protocol inheritance CircleTrivial}}
 
 struct Circle {
   func circle_start() {}

validation-test/compiler_crashers/28799-swift-type-subst-swift-substitutionmap-const-swift-substoptions-const.swift renamed to validation-test/compiler_crashers_fixed/28799-swift-type-subst-swift-substitutionmap-const-swift-substoptions-const.swift

@@ -5,5 +5,5 @@
 // See https://swift.org/LICENSE.txt for license information
 // See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 
-// RUN: not --crash %target-swift-frontend %s -emit-ir
+// RUN: not %target-swift-frontend %s -emit-ir
 protocol P{{}typealias e where f:A:protocol A:A}protocol A:P