Internal compiler error when explicitly instantiating Union of types in same hierarchy

[HertzDevil]

The following produces an internal compiler error since 1.2.0:

class Foo; end
class Bar < Foo; end
Union(Foo, Bar)

BUG: called type_id for Foo+.class (Crystal::VirtualMetaclassType) (Exception)
  from src/compiler/crystal/codegen/llvm_id.cr:43:5 in 'type_id'
  from src/compiler/crystal/codegen/type_id.cr:68:9 in 'type_id_impl'
  from src/compiler/crystal/codegen/type_id.cr:9:5 in 'type_id'
  from src/compiler/crystal/codegen/codegen.cr:1491:15 in 'visit'
  from src/compiler/crystal/syntax/visitor.cr:27:12 in 'accept'
  from src/compiler/crystal/codegen/codegen.cr:2279:7 in 'accept'
  from src/compiler/crystal/codegen/codegen.cr:665:9 in 'visit'
  from src/compiler/crystal/syntax/visitor.cr:27:12 in 'accept'
  from src/compiler/crystal/codegen/codegen.cr:2279:7 in 'accept'
  from src/compiler/crystal/codegen/codegen.cr:69:7 in 'codegen'
  from src/compiler/crystal/codegen/codegen.cr:67:5 in 'codegen:debug:single_module'
  from src/compiler/crystal/progress_tracker.cr:22:7 in 'codegen'
  from src/compiler/crystal/compiler.cr:173:16 in 'compile'
  from src/compiler/crystal/command.cr:309:3 in 'compile'
  from src/compiler/crystal/command.cr:213:14 in 'run_command'
  from src/compiler/crystal/command.cr:122:7 in 'run'
  from src/compiler/crystal/command.cr:51:5 in 'run'
  from src/compiler/crystal/command.cr:50:3 in 'run'
  from src/compiler/crystal.cr:11:1 in '__crystal_main'
  from src/crystal/main.cr:115:5 in 'main_user_code'
  from src/crystal/main.cr:101:7 in 'main'
  from src/crystal/main.cr:127:3 in 'main'
  from /lib/x86_64-linux-gnu/libc.so.6 in '__libc_start_main'
  from .build/crystal in '_start'
  from ???

Foo | Bar is okay. This is most likely a regression of #11188. The solution seems to be devirtualizing the Generic's type ID if it is exactly Union; alternatively, it might involve copying this part:

crystal/src/compiler/crystal/semantic/main_visitor.cr

Lines 208 to 219 in 3963244

	when Type
	# We devirtualize the type because in an expression like
	#
	# T.new
	#
	# even if T is a virtual type that resulted from a generic
	# type argument, creating an instance or invoking methods
	# on the type itself don't need to resolve virtually.
	#
	# It's different if from a virtual type we do `v.class.new`
	# because the class could be any in the hierarchy.
	node.type = check_type_in_type_args(type.remove_alias_if_simple).devirtualize

to here:

crystal/src/compiler/crystal/semantic/bindings.cr

Lines 623 to 624 in 3963244

	generic_type = generic_type.metaclass unless @in_type_args
	self.type = generic_type