[CSDiagnostics] Update UnableToInferGenericPackElementType to accept overloads and update test cases

Author: li3zhen1

lib/Sema/CSBindings.cpp

@@ -2550,14 +2550,12 @@ TypeVariableBinding::fixForHole(ConstraintSystem &cs) const {
   }
 
   if (dstLocator->isLastElement<LocatorPathElt::PackElement>()) {
-
     // A hole appears as an element of generic pack params
     ConstraintFix *Fix = SpecifyPackElementType::create(cs, dstLocator);
     return std::make_pair(Fix, defaultImpact);
   }
 
   return std::nullopt;
-  return std::nullopt;
 }
 
 bool TypeVariableBinding::attempt(ConstraintSystem &cs) const {

lib/Sema/CSDiagnostics.cpp

@@ -8188,49 +8188,46 @@ bool UnableToInferClosureReturnType::diagnoseAsError() {
 }
 
 bool UnableToInferGenericPackElementType::diagnoseAsError() {
-
-  const auto* locator = getLocator();
+  auto *locator = getLocator();
   auto path = locator->getPath();
 
-  if (path.size() > 1) {
-  
-    const auto applyArgToParamElt = (path.end() - 2)->getAs<LocatorPathElt::ApplyArgToParam>();
-    const auto packElementElt = (path.end() - 1)->getAs<LocatorPathElt::PackElement>();
-
-    if (!applyArgToParamElt)
-      return false;
-
-    auto anchor = getAnchor();
+  const auto applyArgToParamElt =
+      (path.end() - 2)->getAs<LocatorPathElt::ApplyArgToParam>();
+  const auto packElementElt =
+      (path.end() - 1)->getAs<LocatorPathElt::PackElement>();
+  if (!applyArgToParamElt || !packElementElt) {
+    return false;
+  }
 
+  if (isExpr<NilLiteralExpr>(getAnchor())) {
     // `nil` appears as an element of generic pack params, let's record a
     // specify contextual type for nil fix.
-    if (isExpr<NilLiteralExpr>(anchor)) {
-      emitDiagnostic(diag::unresolved_nil_literal);
-    }
-    else {
-      // unable to infer the type of an element of generic pack params
-      emitDiagnostic(diag::could_not_infer_pack_element, packElementElt->getIndex());
-    }
+    emitDiagnostic(diag::unresolved_nil_literal);
+  } else {
+    // unable to infer the type of an element of generic pack params
+    emitDiagnostic(diag::could_not_infer_pack_element,
+                   packElementElt->getIndex());
+  }
 
+  if (isExpr<ApplyExpr>(locator->getAnchor())) {
     // emit callee side diagnostics
-    auto applyExpr = castToExpr<ApplyExpr>(locator->getAnchor());
-    if (auto* Fn = applyExpr->getFn()) {
-      if (const auto DeclRef = Fn->getReferencedDecl()) {
-        auto paramDecl = getParameterAt(DeclRef, applyArgToParamElt->getParamIdx());
-        emitDiagnosticAt(
-          paramDecl->getLoc(), diag::note_in_opening_pack_element,
-          packElementElt->getIndex() + 1, paramDecl->getNameStr());
+    if (auto *calleeLocator = getSolution().getCalleeLocator(locator)) {
+      if (const auto choice = getOverloadChoiceIfAvailable(calleeLocator)) {
+        if (auto *decl = choice->choice.getDeclOrNull()) {
+          if (auto paramDecl =
+                  getParameterAt(decl, applyArgToParamElt->getParamIdx())) {
+            emitDiagnosticAt(
+                paramDecl->getLoc(), diag::note_in_opening_pack_element,
+                packElementElt->getIndex() + 1, paramDecl->getNameStr());
+          }
+        }
       }
     }
-
-    return true;
   }
 
-  return false;
+  return true;
 }
 
-
-
 static std::pair<StringRef, StringRef>
 getImportModuleAndDefaultType(const ASTContext &ctx,
                               const ObjectLiteralExpr *expr) {

lib/Sema/ConstraintSystem.cpp

@@ -5881,28 +5881,24 @@ void constraints::simplifyLocator(ASTNode &anchor,
       if (!elt)
         break;
 
-      // If the 3rd element is an PackElement, add the index of pack element within 
-      // packs to locate the correct element.
-      bool hasEltPack = false;
-      unsigned eltPackIdx = 0;
+      // If the 3rd element is an PackElement, add the index of pack element
+      // within packs to locate the correct element.
+      std::optional<unsigned> eltPackIdx;
       if (path.size() > 2) {
-        auto eltPack = path[2].getAs<LocatorPathElt::PackElement>();
-        if (eltPack) {
-          hasEltPack = true;
+        if (auto eltPack = path[2].getAs<LocatorPathElt::PackElement>()) {
           eltPackIdx = eltPack->getIndex();
         }
       }
 
       // Extract application argument.
       if (auto *args = anchorExpr->getArgs()) {
-        if (hasEltPack) {
-          if (elt->getArgIdx() + eltPackIdx < args->size()) {
-            anchor = args->getExpr(elt->getArgIdx() + eltPackIdx);
+        if (eltPackIdx.has_value()) {
+          if (elt->getArgIdx() + eltPackIdx.value() < args->size()) {
+            anchor = args->getExpr(elt->getArgIdx() + eltPackIdx.value());
             path = path.slice(3);
             continue;
           }
-        }
-        else if (elt->getArgIdx() < args->size()) {
+        } else if (elt->getArgIdx() < args->size()) {
           anchor = args->getExpr(elt->getArgIdx());
           path = path.slice(2);
           continue;

test/Constraints/variadic_generic_functions.swift

@@ -97,4 +97,11 @@ do {
   bar(1, 2, 3, nil, "Hello", u: 3, w: 4, 8, nil) // expected-error {{'nil' requires a contextual type}}
   // expected-error@-1 {{'nil' requires a contextual type}}
 
+
+  func fooWithOverload(_ value: Int) {}
+  func fooWithOverload<each T>(_ value: repeat each T) {}
+  // expected-note@-1 {{in inferring pack element #5 of 'value'}}
+
+  fooWithOverload(0, 1, 2, 3, nil) // expected-error {{'nil' requires a contextual type}}
+
 }