Merge pull request #8840 from DougGregor/generic-env-circularity

Author: swift-ci

lib/AST/GenericEnvironment.cpp

@@ -227,6 +227,10 @@ Type GenericEnvironment::QueryArchetypeToInterfaceSubstitutions::operator()(
   auto archetype = type->getAs<ArchetypeType>();
   if (!archetype) return Type();
 
+  // Only top-level archetypes need to be substituted directly; nested
+  // archetypes will be handled via their root archetypes.
+  if (archetype->getParent()) return Type();
+
   // If not all generic parameters have had their context types recorded,
   // perform a linear search.
   auto genericParams = self->Signature->getGenericParams();

validation-test/compiler_crashers_2_fixed/0090-sr4617.swift

@@ -0,0 +1,14 @@
+// RUN: %target-swift-frontend -primary-file %s -emit-ir
+
+extension Dictionary  {
+  init<S: Sequence>(grouping elements: S, by keyForValue: (S.Iterator.Element) -> Key)
+  where Array<S.Iterator.Element> == Value
+  {
+    self = [:]
+    for value in elements {
+      var values = self[keyForValue(value)] ?? []
+      values.append(value)
+      self[keyForValue(value)] = values
+    }
+  }
+}