Merge pull request #39220 from LucianoPAlmeida/SR-15053-overload-diags

[Sema][SR-15053] Ignore ambiguity from conformance in some situations

Author: LucianoPAlmeida

include/swift/AST/Expr.h

@@ -19,14 +19,15 @@
 
 #include "swift/AST/ArgumentList.h"
 #include "swift/AST/Attr.h"
+#include "swift/AST/Availability.h"
 #include "swift/AST/CaptureInfo.h"
 #include "swift/AST/ConcreteDeclRef.h"
+#include "swift/AST/Decl.h"
 #include "swift/AST/DeclContext.h"
 #include "swift/AST/DeclNameLoc.h"
 #include "swift/AST/FunctionRefKind.h"
 #include "swift/AST/ProtocolConformanceRef.h"
 #include "swift/AST/TypeAlignments.h"
-#include "swift/AST/Availability.h"
 #include "swift/Basic/Debug.h"
 #include "swift/Basic/InlineBitfield.h"
 #include "llvm/Support/TrailingObjects.h"
@@ -1453,6 +1454,8 @@ class OverloadedDeclRefExpr final : public OverloadSetRefExpr {
   SourceLoc getLoc() const { return Loc.getBaseNameLoc(); }
   SourceRange getSourceRange() const { return Loc.getSourceRange(); }
 
+  bool isForOperator() const { return getDecls().front()->isOperator(); }
+
   static bool classof(const Expr *E) {
     return E->getKind() == ExprKind::OverloadedDeclRef;
   }

include/swift/Sema/ConstraintLocator.h

@@ -1106,6 +1106,14 @@ class ConstraintLocatorBuilder {
     return false;
   }
 
+  bool isForRequirement(RequirementKind kind) const {
+    if (auto lastElt = last()) {
+      auto requirement = lastElt->getAs<LocatorPathElt::AnyRequirement>();
+      return requirement && kind == requirement->getRequirementKind();
+    }
+    return false;
+  }
+
   /// Checks whether this locator is describing an argument application for a
   /// non-ephemeral parameter.
   bool isNonEphemeralParameterApplication() const {

lib/Sema/CSSimplify.cpp

@@ -1864,6 +1864,18 @@ assessRequirementFailureImpact(ConstraintSystem &cs, Type requirementType,
     if (!cs.findSelectedOverloadFor(calleeLoc))
       return 10;
   }
+  
+  auto resolvedTy = cs.simplifyType(requirementType);
+
+  // Increase the impact of a conformance fix for generic parameters on
+  // operators where such conformance failures are not as important as argument
+  // mismatches or contextual failures.
+  if (auto *ODRE = getAsExpr<OverloadedDeclRefExpr>(anchor)) {
+    if (locator.isForRequirement(RequirementKind::Conformance) &&
+        resolvedTy->is<ArchetypeType>() && ODRE->isForOperator()) {
+      ++impact;
+    }
+  }
 
   // Increase the impact of a conformance fix for a standard library
   // or foundation type, as it's unlikely to be a good suggestion.
@@ -1876,16 +1888,11 @@ assessRequirementFailureImpact(ConstraintSystem &cs, Type requirementType,
   // rdar://60727310. Once we better handle the separation of conformance fixes
   // from argument mismatches in cases like SR-12438, we should be able to
   // remove it from the condition.
-  auto resolvedTy = cs.simplifyType(requirementType);
   if ((requirementType->is<TypeVariableType>() && resolvedTy->isStdlibType()) ||
       resolvedTy->isAny() || resolvedTy->isAnyObject() ||
       getKnownFoundationEntity(resolvedTy->getString())) {
-    if (auto last = locator.last()) {
-      if (auto requirement = last->getAs<LocatorPathElt::AnyRequirement>()) {
-        auto kind = requirement->getRequirementKind();
-        if (kind == RequirementKind::Conformance)
-          impact += 2;
-      }
+    if (locator.isForRequirement(RequirementKind::Conformance)) {
+      impact += 2;
     }
   }
 

test/Constraints/diag_ambiguities.swift

@@ -68,3 +68,13 @@ class MoviesViewController {
     _ = itemType // expected-error {{ambiguous use of 'itemType'}}
   }
 }
+
+// SR-15053
+func SR15053<T : Numeric>(_ a: T, _ b: T) -> T {
+  (a + b) / 2 // expected-error{{cannot convert return expression of type 'Int' to return type 'T'}}
+  // expected-error@-1{{cannot convert value of type 'T' to expected argument type 'Int'}}
+}
+
+func SR15053<T : Numeric>(_ a: T, _ b: T) {
+  (a + b) / 2 // expected-error{{cannot convert value of type 'T' to expected argument type 'Int'}}
+}

test/Constraints/rdar40002266.swift

@@ -6,6 +6,6 @@ import Foundation
 struct S {
   init<T: NSNumber>(_ num: T) { // expected-note {{where 'T' = 'Bool'}}
     self.init(num != 0) // expected-error {{initializer 'init(_:)' requires that 'Bool' inherit from 'NSNumber'}}
-    // expected-error@-1 {{referencing operator function '!=' on 'BinaryInteger' requires that 'T' conform to 'BinaryInteger'}}
+    // expected-error@-1 {{cannot convert value of type 'T' to expected argument type 'Int'}}
   }
 }