spec: Interface method specifiers

[nhooyr]

The spec says this: https://golang.org/ref/spec#MethodSpec

An interface type specifies a method set called its interface. A variable of interface type can store a value of any type with a method set that is any superset of the interface. Such a type is said to implement the interface. The value of an uninitialized variable of interface type is nil.

InterfaceType = "interface" "{" { MethodSpec ";" } "}" .
MethodSpec = MethodName Signature | InterfaceTypeName .
MethodName = identifier .
InterfaceTypeName = TypeName .

Shouldn't the MethodSpec be equal to (MethodName Signature) | InterfaceTypeName?

Because that implies that you can have a MethodName next to a InterfaceTypeName and it will be valid? But having the parentheses means that those are grouped together, thus you either get InterfaceTypeName or MethodName + Signature.

[griesemer]

Per http://golang.org/ref/spec#Notation, in EBNF the "or" operator "|" binds less strong than its Alternatives. So:

MethodSpec = MethodName Signature | InterfaceTypeName .

is the same as:

MethodSpec = (MethodName Signature) | InterfaceTypeName .

Or in other words, parentheses are not needed in this case.