Merge pull request #21295 from aschwaighofer/silgen_soften_assertion_in_project_open_opaque_existential_5.0

[5.0] SILGen: Soften assertions it is okay for an base value of an bo…

Author: eeckstein

lib/SILGen/SILGenLValue.cpp

@@ -843,8 +843,11 @@ namespace {
                          ManagedValue base) && override {
       assert(base.getType().isExistentialType() &&
              "base for open existential component must be an existential");
-      assert(base.getType().isAddress() &&
-             "base value of open-existential component was not an address?");
+      assert((base.getType().isAddress() ||
+              base.getType().getPreferredExistentialRepresentation(SGF.SGM.M) ==
+                  ExistentialRepresentation::Boxed) &&
+             "base value of open-existential component was not an address or a "
+             "boxed existential?");
       SILValue addr;
 
       auto rep = base.getType().getPreferredExistentialRepresentation(SGF.SGM.M);

test/SILGen/boxed_existentials.swift

@@ -223,3 +223,21 @@ func erasure_to_any(_ guaranteed: Error, _ immediate: Error) -> Any {
     return plusOneError()
   }
 }
+
+extension Error {
+  var myError: Error {
+    return self
+  }
+}
+
+// Make sure we don't assert on this.
+// CHECK-LABEL: sil hidden @$s18boxed_existentials4testyyF
+// CHECK:  [[ERROR_ADDR:%.*]] = alloc_stack $Error
+// CHECK:  [[ARRAY_GET:%.*]] = function_ref @$sSayxSicig
+// CHECK:  apply [[ARRAY_GET]]<Error>([[ERROR_ADDR]]
+// CHECK:  [[ERROR:%.*]] = load [take] [[ERROR_ADDR]] : $*Error
+// CHECK:  open_existential_box [[ERROR]]
+func test() {
+  var errors: [Error] = []
+  test_property(errors[0].myError)
+}