Syntax-lookup pages whose examples do not compile #1397

operators_mod.mdx:18, decorator_gentype.mdx:19,24, decorator_unboxed.mdx:20, language_module_type.mdx:26, language_labeled_argument.mdx:17; deprecated extension_regular_expression, decorator_send_pipe give no notice.

language_spreads.mdx:83 spreads ...dog, a type the page never defines (the type is pets, :77): "This type constructor, dog, can't be found". Compiled per example, 2 blocks fail to parse and 13 fail to type-check, on 13 pages.

Line numbers refer to master at ff3eac6.