spec: remove unnecessary syntax restrictions for method expressions to match compiler #9060
Description
At the moment, method expressions must be of the form T.m or (*T).m . There's no good reason not to generalize the notation to T.m where T is any kind of type that has a method m. The only options are the ones we already have, as well as unnamed interface types and struct type embedding fields with methods. These extra cases are largely academic but there's no real reason for the restriction; it only adds complexity to the spec and requires extra checks in the compiler. This would be a backward-compatible language change w/o impact to users. It would simplify the spec. It simplifies the type-checker. It may simplify the rest of the implementation. See also issue #8605.