Fix SILGen to generate switch_enum at +1 for opaque value operand

Author: meg-gupta

lib/SILGen/SILGenPattern.cpp

@@ -2850,7 +2850,11 @@ void SILGenFunction::emitSwitchStmt(SwitchStmt *S) {
     }
 
     // If then we have an object, return it at +0.
+    // For opaque values, return at +1
     if (subjectMV.getType().isObject()) {
+      if (subjectMV.getType().isAddressOnly(F)) {
+        return {subjectMV.copy(*this, S), CastConsumptionKind::TakeAlways};
+      }
       return {subjectMV, CastConsumptionKind::BorrowAlways};
     }
 

test/SILGen/opaque_values_silgen.swift

@@ -461,3 +461,20 @@ class TestGeneric<T> {
 // CHECK:   unwind
 // CHECK-LABEL: } // end sil function '$s20opaque_values_silgen11TestGenericC08borrowedE0xvr'
 
+// CHECK-LABEL: sil hidden [ossa] @$s20opaque_values_silgen8TestEnumO5_codeSivg :
+// CHECK: bb0(%0 : @guaranteed $TestEnum<T>):
+// CHECK:   [[COPY:%.*]] = copy_value %0 : $TestEnum<T>
+// CHECK:   switch_enum [[COPY]] : $TestEnum<T>, case #TestEnum.invalidValue!enumelt: bb1
+// CHECK: bb1([[VAL:%.*]] : @owned $Any):
+// CHECK:   destroy_value [[VAL]] : $Any
+// CHECK-LABEL: } // end sil function '$s20opaque_values_silgen8TestEnumO5_codeSivg'
+enum TestEnum<T> {
+  case invalidValue(Any)
+
+  var _code: Int {
+     switch self {
+     case .invalidValue: return 4866
+     }
+  }
+}
+