Merge pull request swiftlang#39039 from LucianoPAlmeida/SR-14408-ambiguity-enum

[Sema][SR-14408] Improvements on enum equality diagnostics

Author: LucianoPAlmeida

lib/Sema/CSSimplify.cpp

@@ -8251,6 +8251,13 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyMemberConstraint(
       if (instanceTy->isAny() || instanceTy->isAnyObject())
         impact += 5;
 
+      // Increasing the impact for missing member in any argument position so it
+      // doesn't affect situations where there are another fixes involved.
+      auto *anchorExpr = getAsExpr(locator->getAnchor());
+      if (anchorExpr && isArgumentExpr(anchorExpr)) {
+        impact += 5;
+      }
+
       if (recordFix(fix, impact))
         return SolutionKind::Error;
 
@@ -8301,7 +8308,7 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyMemberConstraint(
                               functionRefKind, locator,
                               /*includeInaccessibleMembers*/ true);
 
-      // If uwrapped type still couldn't find anything for a given name,
+      // If unwrapped type still couldn't find anything for a given name,
       // let's fallback to a "not such member" fix.
       if (result.ViableCandidates.empty() && result.UnviableCandidates.empty())
         return fixMissingMember(origBaseTy, memberTy, locator);

lib/Sema/ConstraintSystem.cpp

@@ -4934,6 +4934,15 @@ ConstraintSystem::isArgumentExpr(Expr *expr) {
     return None;
   }
 
+  // Specifically for unresolved member expr getParentExpr returns a chain
+  // result expr as its immediate parent, so let's look one level up on AST.
+  if (auto *URMCR = getAsExpr<UnresolvedMemberChainResultExpr>(argList)) {
+    argList = getParentExpr(URMCR);
+    if (!argList) {
+      return None;
+    }
+  }
+
   if (isa<ParenExpr>(argList)) {
     for (;;) {
       auto *parent = getParentExpr(argList);

test/Constraints/enum_cases.swift

@@ -171,3 +171,28 @@ struct EnumElementPatternFromContextualType<T> {
     }
   }
 }
+
+// SR-14408
+enum CompassPoint {
+    case North(Int)
+    case South
+    case East
+    case West
+}
+
+func isNorth(c : CompassPoint) -> Bool {
+  // expected-error@+1{{member 'North' expects argument of type 'Int'}}
+  return c == .North // expected-error {{binary operator '==' cannot be applied to two 'CompassPoint' operands}}
+  // expected-note@-1 {{binary operator '==' cannot be synthesized for enums with associated values}}
+}
+
+func isNorth2(c : CompassPoint) -> Bool {
+  // expected-error@+1{{member 'North' expects argument of type 'Int'}}
+  return .North == c // expected-error {{binary operator '==' cannot be applied to two 'CompassPoint' operands}}
+  // expected-note@-1 {{binary operator '==' cannot be synthesized for enums with associated values}}
+}
+
+func isSouth(c : CompassPoint) -> Bool {
+  return c == .South // expected-error {{binary operator '==' cannot be applied to two 'CompassPoint' operands}}
+  // expected-note@-1 {{binary operator '==' cannot be synthesized for enums with associated values}}
+}