[Sema] EffectsChecker: Adjust application classifier to skip invertible protocol requirements

Refactors application classifier to center around substitution map
and strip invertible protocol requirements that have no effect.

Resolves: rdar://123356909

Author: xedin

lib/Sema/TypeCheckEffects.cpp

@@ -1302,8 +1302,13 @@ class ApplyClassifier {
     if (!fnType) return Classification::forInvalidCode();
 
     auto fnRef = AbstractFunction::getAppliedFn(E);
-    auto conformances = fnRef.getSubstitutions().getConformances();
-    const auto hasAnyConformances = !conformances.empty();
+    auto substitutions = fnRef.getSubstitutions();
+    const bool hasAnyConformances =
+        llvm::any_of(substitutions.getConformances(),
+                     [](const ProtocolConformanceRef conformance) {
+                       auto *requirement = conformance.getRequirement();
+                       return !requirement->getInvertibleProtocolKind();
+                     });
 
     // If the function doesn't have any effects or conformances, we're done
     // here.
@@ -1347,21 +1352,21 @@ class ApplyClassifier {
       switch (auto polyKind = fnRef.getPolymorphicEffectKind(kind)) {
       case PolymorphicEffectKind::AsyncSequenceRethrows:
       case PolymorphicEffectKind::ByConformance: {
-        auto substitutions = fnRef.getSubstitutions();
-        auto requirements =
-            substitutions.getGenericSignature().getRequirements();
-        auto conformances = substitutions.getConformances();
+        auto requirements = substitutions.getGenericSignature()
+                                .withoutMarkerProtocols()
+                                .getRequirements();
         for (const auto &req : requirements) {
           if (req.getKind() != RequirementKind::Conformance)
             continue;
 
-          auto conformanceRef = conformances.front();
-          conformances = conformances.drop_front();
-
           Type type = req.getFirstType().subst(substitutions);
+
+          auto conformanceRef = substitutions.lookupConformance(
+              req.getFirstType()->getCanonicalType(), req.getProtocolDecl());
+          assert(conformanceRef);
+
           result.merge(classifyConformance(type, conformanceRef, kind));
         }
-        assert(conformances.empty());
 
         // 'ByConformance' is a superset of 'ByClosure', so check for
         // closure arguments too.

test/Concurrency/async_throwing.swift

@@ -150,3 +150,28 @@ func asyncTest() async {
     // ignore
   }
 }
+
+// rdar://123356909 - spurious error - `call can throw, but it is not marked with 'try' and the error is not handled`
+do {
+  struct AsyncTestSequence<Element>: AsyncSequence {
+    typealias Element = Element
+
+    let stream: AsyncMapSequence<AsyncStream<[String : Any]>, Element>
+
+    init(stream: AsyncMapSequence<AsyncStream<[String : Any]>, Element>) {
+      self.stream = stream
+    }
+
+    func makeAsyncIterator() -> AsyncIterator {
+      .init(iterator: stream.makeAsyncIterator())
+    }
+
+    struct AsyncIterator: AsyncIteratorProtocol {
+      var iterator: AsyncMapSequence<AsyncStream<[String : Any]>, Element>.AsyncIterator
+
+      mutating func next() async -> Element? {
+        await iterator.next() // Ok
+      }
+    }
+  }
+}