Sema: Clean up leading dot fix logic in simplifyConformsToConstraint()

Tests still pass without this code, including the tests I just
added in the previous commit.

Author: slavapestov

lib/Sema/CSSimplify.cpp

@@ -8859,17 +8859,14 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyConformsToConstraint(
     return SolutionKind::Solved;
   }
 
-  auto formUnsolved = [&](bool activate = false) {
+  auto formUnsolved = [&]() {
     // If we're supposed to generate constraints, do so.
     if (flags.contains(TMF_GenerateConstraints)) {
       auto *conformance = Constraint::create(
           *this, kind, type, protocol->getDeclaredInterfaceType(),
           getConstraintLocator(locator));
 
       addUnsolvedConstraint(conformance);
-      if (activate)
-        activateConstraint(conformance);
-
       return SolutionKind::Solved;
     }
 
@@ -9243,46 +9240,41 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyConformsToConstraint(
 
       if (isExpr<UnresolvedMemberExpr>(anchor) &&
           req->is<LocatorPathElt::TypeParameterRequirement>()) {
+        auto *memberLoc = getConstraintLocator(anchor, path.front());
+
         auto signature = path[path.size() - 2]
                              .castTo<LocatorPathElt::OpenedGeneric>()
                              .getSignature();
         auto requirement = signature.getRequirements()[req->getIndex()];
 
-        auto *memberLoc = getConstraintLocator(anchor, path.front());
-        auto overload = findSelectedOverloadFor(memberLoc);
-
-        // To figure out what is going on here we need to wait until
-        // member overload is set in the constraint system.
-        if (!overload) {
-          // If it's not allowed to generate new constraints
-          // there is no way to control re-activation, so this
-          // check has to fail.
-          if (!flags.contains(TMF_GenerateConstraints))
-            return SolutionKind::Error;
+        auto attemptInvalidStaticMemberRefOnMetatypeFix = [&]() {
+          // If the failed requirement isn't the first generic parameter,
+          // it can't be a static member reference on a protocol metatype.
+          if (!requirement.getFirstType()->isEqual(getASTContext().TheSelfType))
+            return false;
 
-          return formUnsolved(/*activate=*/true);
-        }
+          // If we don't know the overload yet, conservatively assume it's
+          // a static member reference on a protocol metatype.
+          auto overload = findSelectedOverloadFor(memberLoc);
+          if (!overload)
+            return true;
 
-        auto *memberRef = overload->choice.getDeclOrNull();
-        if (!memberRef)
-          return SolutionKind::Error;
+          auto *decl = overload->choice.getDeclOrNull();
+          if (!decl)
+            return true;
 
-        // If this is a `Self` conformance requirement from a static member
-        // reference on a protocol metatype, let's produce a tailored diagnostic.
-        if (memberRef->isStatic()) {
-          if (hasFixFor(memberLoc,
-                        FixKind::AllowInvalidStaticMemberRefOnProtocolMetatype))
-            return SolutionKind::Solved;
+          // Otherwise, we can do a precise check.
+          if (!decl->isStatic())
+            return false;
 
-          if (auto *protocolDecl =
-                  memberRef->getDeclContext()->getSelfProtocolDecl()) {
-            auto selfTy = protocolDecl->getSelfInterfaceType();
-            if (selfTy->isEqual(requirement.getFirstType())) {
-              auto *fix = AllowInvalidStaticMemberRefOnProtocolMetatype::create(
-                *this, memberLoc);
-              return recordFix(fix) ? SolutionKind::Error : SolutionKind::Solved;
-            }
-          }
+          return decl->getDeclContext()->getSelfProtocolDecl() != nullptr;
+        };
+
+        if (attemptInvalidStaticMemberRefOnMetatypeFix()) {
+          auto *fix = AllowInvalidStaticMemberRefOnProtocolMetatype::create(
+              *this, memberLoc);
+
+          return recordFix(fix) ? SolutionKind::Error : SolutionKind::Solved;
         }
       }
 

test/Constraints/static_members_on_protocol_in_generic_context.swift

@@ -177,7 +177,7 @@ test_combo(.genericFn(42)) // expected-error {{global function 'test_combo' requ
 
 extension P { // expected-note 13 {{missing same-type requirement on 'Self'}} {{12-12= where Self == <#Type#>}}
   static func generic<T>(_: T) -> T { fatalError() }
-  static func genericWithReqs<T: Collection, Q>(_: T) -> Q where T.Element == Q { // expected-note {{required by static method 'genericWithReqs' where 'T' = '()'}}
+  static func genericWithReqs<T: Collection, Q>(_: T) -> Q where T.Element == Q { // expected-note 3 {{required by static method 'genericWithReqs' where 'T' = '()'}}
     fatalError()
   }
 }
@@ -246,7 +246,9 @@ test(.genericWithReqs([S()])) // expected-error {{contextual member reference to
 test(.genericWithReqs([42]))
 // expected-error@-1 {{contextual member reference to static method 'genericWithReqs' requires 'Self' constraint in the protocol extension}}
 test(.genericWithReqs(()))
-// expected-error@-1 {{contextual member reference to static method 'genericWithReqs' requires 'Self' constraint in the protocol extension}}
+// expected-error@-1 {{type '()' cannot conform to 'Collection'}}
+// expected-note@-2 {{only concrete types such as structs, enums and classes can conform to protocols}}
+// expected-error@-3 {{contextual member reference to static method 'genericWithReqs' requires 'Self' constraint in the protocol extension}}
 
 test_combo(.doesntExist) // expected-error {{reference to member 'doesntExist' cannot be resolved without a contextual type}}
 test_combo(.doesnt.exist()) // expected-error {{reference to member 'doesnt' cannot be resolved without a contextual type}}
@@ -262,7 +264,9 @@ test_combo(.genericWithReqs([S()])) // expected-error {{contextual member refere
 test_combo(.genericWithReqs([42]))
 // expected-error@-1 {{contextual member reference to static method 'genericWithReqs' requires 'Self' constraint in the protocol extension}}
 test_combo(.genericWithReqs(()))
-// expected-error@-1 {{contextual member reference to static method 'genericWithReqs' requires 'Self' constraint in the protocol extension}}
+// expected-error@-1 {{type '()' cannot conform to 'Collection'}}
+// expected-note@-2 {{only concrete types such as structs, enums and classes can conform to protocols}}
+// expected-error@-3 {{contextual member reference to static method 'genericWithReqs' requires 'Self' constraint in the protocol extension}}
 
 protocol TestWithAssoc {
   associatedtype U