[CSDiagnostics] Update test cases for variadic generic functions

Author: li3zhen1

lib/Sema/CSDiagnostics.cpp

@@ -8203,13 +8203,8 @@ bool UnableToInferGenericPackElementType::diagnoseAsError() {
   auto *locator = getLocator();
   auto path = locator->getPath();
 
-  const auto applyArgToParamElt =
-      (path.end() - 2)->getAs<LocatorPathElt::ApplyArgToParam>();
-  const auto packElementElt =
-      (path.end() - 1)->getAs<LocatorPathElt::PackElement>();
-  if (!applyArgToParamElt || !packElementElt) {
-    return false;
-  }
+  auto packElementElt = locator->getLastElementAs<LocatorPathElt::PackElement>();
+  assert(packElementElt && "Expected path to end with a pack element locator");
 
   if (isExpr<NilLiteralExpr>(getAnchor())) {
     // `nil` appears as an element of generic pack params, let's record a
@@ -8226,6 +8221,8 @@ bool UnableToInferGenericPackElementType::diagnoseAsError() {
     if (auto *calleeLocator = getSolution().getCalleeLocator(locator)) {
       if (const auto choice = getOverloadChoiceIfAvailable(calleeLocator)) {
         if (auto *decl = choice->choice.getDeclOrNull()) {
+          const auto applyArgToParamElt =
+              (path.end() - 2)->getAs<LocatorPathElt::ApplyArgToParam>();
           if (auto paramDecl =
                   getParameterAt(decl, applyArgToParamElt->getParamIdx())) {
             emitDiagnosticAt(

test/Constraints/pack_expansion_types.swift

@@ -243,8 +243,10 @@ func patternInstantiationConcreteValid() {
 func patternInstantiationConcreteInvalid() {
   let _: Set<Int> = patternInstantiationTupleTest1()
   // expected-error@-1 {{cannot convert value of type '(repeat Array<_>)' to specified type 'Set<Int>'}}
+  // expected-error@-2 {{could not infer pack element #0 from context}}
 
   let _: (Array<Int>, Set<String>) = patternInstantiationTupleTest1() // expected-error {{'(repeat Array<Int, _>)' is not convertible to '(Array<Int>, Set<String>)', tuples have a different number of elements}}
+  // expected-error@-1 {{could not infer pack element #1 from context}}
 }
 
 func patternInstantiationGenericValid<each T, each U>(t: repeat each T, u: repeat each U)
@@ -275,6 +277,7 @@ func patternInstantiationGenericInvalid<each T: Hashable>(t: repeat each T) {
   // expected-error@-1 {{generic parameter 'each T' could not be inferred}}
 
   let _: (repeat Array<each T>, Set<String>) = patternInstantiationTupleTest1() // expected-error {{'(repeat Array<repeat each T, _>)' is not convertible to '(repeat Array<each T>, Set<String>)', tuples have a different number of elements}}
+  // expected-error@-1 {{could not infer pack element #1 from context}}
 }
 
 // rdar://107996926 - Vanishing metatype of tuple not supported

test/Constraints/variadic_generic_functions.swift

@@ -83,24 +83,24 @@ do {
 
 // apple/swift#69432 - Passing nil to a parameter pack fails to produce diagnostic for expression
 do {
-  func foo<each T>(_ value: repeat each T) {} // expected-note {{in inferring pack element #1 of 'value'}}
-  // expected-note@-1 {{in inferring pack element #1 of 'value'}}
-  // expected-note@-2 {{in inferring pack element #2 of 'value'}}
+  func foo<each T>(_ value: repeat each T) {} // expected-note {{in inferring pack element #0 of 'value'}}
+  // expected-note@-1 {{in inferring pack element #0 of 'value'}}
+  // expected-note@-2 {{in inferring pack element #1 of 'value'}}
 
   foo(nil) // expected-error {{'nil' requires a contextual type}}
   foo(nil, 1) // expected-error {{'nil' requires a contextual type}}
   foo(2, nil) // expected-error {{'nil' requires a contextual type}}
 
-  func bar<each T, U, each W>(_ t: repeat each T, u: U, w: repeat each W) {} // expected-note {{in inferring pack element #3 of 'w'}}
-  // expected-note@-1 {{in inferring pack element #4 of 't'}}
+  func bar<each T, U, each W>(_ t: repeat each T, u: U, w: repeat each W) {} // expected-note {{in inferring pack element #2 of 'w'}}
+  // expected-note@-1 {{in inferring pack element #3 of 't'}}
 
   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'}}
+  // expected-note@-1 {{in inferring pack element #4 of 'value'}}
 
   fooWithOverload(0, 1, 2, 3, nil) // expected-error {{'nil' requires a contextual type}}
 

test/Constraints/variadic_generic_types.swift

@@ -106,3 +106,15 @@ do {
     }
   }
 }
+
+// apple/swift#69432 - Passing nil to a parameter pack fails to produce diagnostic for expression
+do {
+  struct Foo<each T> {
+    init(_ value: repeat each T) {}
+    // expected-note@-1 {{in inferring pack element #0 of 'value'}}
+    // expected-note@-2 {{in inferring pack element #0 of 'value'}}
+  }
+
+  _ = Foo(nil) // expected-error {{'nil' requires a contextual type}}
+  _ = Foo(nil, 1) // expected-error {{'nil' requires a contextual type}}
+}