[CSFix] Use fully qualified locators for requirement failures

lib/Sema/CSDiagnostics.cpp

@@ -86,7 +86,9 @@ Expr *FailureDiagnostic::findParentExpr(Expr *subExpr) const {
 }
 
 Type RequirementFailure::getOwnerType() const {
-  return getType(getAnchor())->getInOutObjectType()->getMetatypeInstanceType();
+  return getType(getRawAnchor())
+      ->getInOutObjectType()
+      ->getMetatypeInstanceType();
 }
 
 const GenericContext *RequirementFailure::getGenericContext() const {

lib/Sema/CSDiagnostics.h

@@ -203,7 +203,7 @@ class RequirementFailure : public FailureDiagnostic {
     if (!expr)
       return;
 
-    if (auto *parentExpr = findParentExpr(getAnchor()))
+    if (auto *parentExpr = findParentExpr(getRawAnchor()))
       Apply = dyn_cast<ApplyExpr>(parentExpr);
   }
 
@@ -254,12 +254,31 @@ class RequirementFailure : public FailureDiagnostic {
     if (isConditional())
       return true;
 
+    auto *anchor = getAnchor();
+    // In the situations like this:
+    //
+    // ```swift
+    // enum E<T: P> { case foo(T) }
+    // let _: E = .foo(...)
+    // ```
+    //
+    // `E` is going to be opened twice. First, when
+    // it's used as a contextual type, and when `E.foo`
+    // is found and its function type is opened.
+    // We still want to record both fixes but should
+    // avoid diagnosing the same problem multiple times.
+    if (isa<UnresolvedMemberExpr>(anchor)) {
+      auto path = getLocator()->getPath();
+      if (path.front().getKind() != ConstraintLocator::UnresolvedMember)
+        return false;
+    }
+
     // For static/initializer calls there is going to be
     // a separate fix, attached to the argument, which is
     // much easier to diagnose.
     // For operator calls we can't currently produce a good
     // diagnostic, so instead let's refer to expression diagnostics.
-    return !(Apply && (isOperator(Apply) || isa<TypeExpr>(getAnchor())));
+    return !(Apply && (isOperator(Apply) || isa<TypeExpr>(anchor)));
   }
 
   static bool isOperator(const ApplyExpr *apply) {

lib/Sema/CSSimplify.cpp

@@ -1612,29 +1612,22 @@ static ConstraintFix *fixRequirementFailure(ConstraintSystem &cs, Type type1,
   if (type1->hasDependentMember() || type2->hasDependentMember())
     return nullptr;
 
-  auto reqPath = path.take_back(2);
-  auto req = reqPath.back();
-
-  ConstraintLocator *reqLoc = nullptr;
+  auto req = path.back();
   if (req.isConditionalRequirement()) {
     // path is - ... -> open generic -> type req # -> cond req #,
     // to identify type requirement we only need `open generic -> type req #`
     // part, because that's how fixes for type requirements are recorded.
-    reqPath = path.drop_back().take_back(2);
+    auto reqPath = path.drop_back();
     // If underlying conformance requirement has been fixed,
     // then there is no reason to fix up conditional requirements.
     if (cs.hasFixFor(cs.getConstraintLocator(anchor, reqPath,
                                              /*summaryFlags=*/0)))
       return nullptr;
-
-    // For conditional requirements we need a full path.
-    reqLoc = cs.getConstraintLocator(anchor, path, /*summaryFlags=*/0);
-  } else {
-    // Build simplified locator which only contains anchor and requirement info.
-    reqLoc = cs.getConstraintLocator(anchor, reqPath,
-                                     /*summaryFlags=*/0);
   }
 
+  auto *reqLoc = cs.getConstraintLocator(anchor, path,
+                                         /*summaryFlags=*/0);
+
   auto reqKind = static_cast<RequirementKind>(req.getValue2());
   switch (reqKind) {
   case RequirementKind::SameType: {
@@ -2789,32 +2782,20 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyConformsToConstraint(
 
     if (path.back().isTypeParameterRequirement() ||
         path.back().isConditionalRequirement()) {
-      ConstraintLocator *reqLoc = nullptr;
       if (path.back().isConditionalRequirement()) {
-        // Drop 'conditional requirement' element remainder
+        // Drop 'conditional requirement' element, remainder
         // of the path is going to point to type requirement
         // this conditional comes from.
         auto reqPath = ArrayRef<LocatorPathElt>(path).drop_back();
         // Underlying conformance requirement is itself fixed,
         // this wouldn't lead to a right solution.
-        if (hasFixFor(getConstraintLocator(anchor, reqPath.take_back(2),
+        if (hasFixFor(getConstraintLocator(anchor, reqPath,
                                            /*summaryFlags=*/0)))
           return SolutionKind::Error;
-
-        // For conditional requirements we need complete path, which includes
-        // type requirement position, to be able to fetch conformance later.
-        reqLoc = getConstraintLocator(locator);
-      } else {
-        // Let's strip all of the unnecessary information from locator,
-        // diagnostics only care about anchor - to lookup type,
-        // generic signature where requirement comes from, and
-        // what was the requirement# which is not satisfied.
-        auto reqPath = ArrayRef<LocatorPathElt>(path).take_back(2);
-        reqLoc = getConstraintLocator(anchor, reqPath,
-                                      /*summaryFlags=*/0);
       }
 
-      auto *fix = MissingConformance::create(*this, type, protocol, reqLoc);
+      auto *fix = MissingConformance::create(*this, type, protocol,
+                                             getConstraintLocator(locator));
       if (!recordFix(fix))
         return SolutionKind::Solved;
     }