InitializeStaticGlobals: fix handling of nested non-loadable enums

Fixes a compiler crash
rdar://160880083

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/InitializeStaticGlobals.swift

@@ -233,17 +233,15 @@ private indirect enum GlobalInitValue {
   }
 
   private mutating func setEnumCase(to value: InitValue, at path: SmallProjectionPath, index: Int, type: Type) -> Bool {
-    switch value {
+    if path.isEmpty, case .enumCaseWithoutPayload(let iea) = value {
 
-    case .enumCaseWithoutPayload(let iea):
       guard case .undefined = self else {
         // The enum was set twice.
         return false
       }
       assert(index == iea.caseIndex)
       self = .enumCase(caseIndex: index)
-
-    case .value:
+    } else {
       guard let payloadType = type.getEnumCases(in: value.parentFunction)!.getPayloadType(ofCaseIndex: index) else {
         return false
       }

test/SILOptimizer/init_static_globals.sil

@@ -37,6 +37,15 @@ struct TwoFields {
   let b: Int32
 }
 
+struct WithOptionalEnum {
+  var e: E?
+}
+
+enum E {
+  case a
+  case b
+}
+
 @_rawLayout(like: Int32)
 struct Raw: ~Copyable {}
 
@@ -183,6 +192,13 @@ sil_global [let] @gIndirectNone: $Optional<TwoFields>
 // CHECK-NEXT:  }
 sil_global [let] @gIndirectSome: $Optional<TwoFields>
 
+// CHECK-LABEL: sil_global [let] @structWithOptionalEnum : $WithOptionalEnum = {
+// CHECK-NEXT:    %0 = enum $E, #E.a!enumelt
+// CHECK-NEXT:    %1 = enum $Optional<E>, #Optional.some!enumelt, %0
+// CHECK-NEXT:    %initval = struct $WithOptionalEnum (%1)
+// CHECK-NEXT:  }
+sil_global [let] @structWithOptionalEnum : $WithOptionalEnum
+
 sil @unknownfunc : $@convention(thin) () -> ()
 
 // CHECK-LABEL: sil [global_init_once_fn] [ossa] @globalinit_trivialglobal_func :
@@ -620,3 +636,15 @@ bb0:
   return %10 : $()
 }
 
+sil [global_init_once_fn] @globalinit_structWithOptionalEnum : $@convention(c) (Builtin.RawPointer) -> () {
+bb0(%0 : $Builtin.RawPointer):
+  alloc_global @structWithOptionalEnum
+  %2 = global_addr @structWithOptionalEnum : $*WithOptionalEnum
+  %3 = struct_element_addr %2, #WithOptionalEnum.e
+  %4 = init_enum_data_addr %3, #Optional.some!enumelt
+  inject_enum_addr %4, #E.a!enumelt
+  inject_enum_addr %3, #Optional.some!enumelt
+  %7 = tuple ()
+  return %7
+}
+