Method methodDecl

syntax/parser.go:1709–1821

MethodSpec = MethodName Signature | InterfaceTypeName . MethodName = identifier . InterfaceTypeName = TypeName .

()

// MethodName        = identifier .
// InterfaceTypeName = TypeName .
func (p *parser) methodDecl() *Field {
	if trace {
		defer p.trace("methodDecl")()
	}

	f := new(Field)
	f.pos = p.pos()
	name := p.name()

	// accept potential name list but complain
	// TODO(gri) We probably don't need this special check anymore.
	//           Nobody writes this kind of code. It's from ancient
	//           Go beginnings.
	hasNameList := false
	for p.got(_Comma) {
		p.name()
		hasNameList = true
	}
	if hasNameList {
		p.syntaxError("name list not allowed in interface type")
		// already progressed, no need to advance
	}

	const context = "interface method"

	switch p.tok {
	case _Lparen:
		// method
		f.Name = name
		f.Type = p.funcType(context, nil)

	case _Lbrack:
		if p.allowGenerics() {
			// Careful dance: We don't know if we have a generic method m[T C](x T)
			// or an embedded instantiated type T[P1, P2] (we accept generic methods
			// for generality and robustness of parsing).
			pos := p.pos()
			p.next()

			// Empty type parameter or argument lists are not permitted.
			// Treat as if [] were absent.
			if p.tok == _Rbrack {
				// name[]
				pos := p.pos()
				p.next()
				if p.tok == _Lparen {
					// name[](
					p.errorAt(pos, "empty type parameter list")
					f.Name = name
					f.Type = p.funcType(context, nil)
				} else {
					p.errorAt(pos, "empty type argument list")
					f.Type = name
				}
				break
			}

			// A type argument list looks like a parameter list with only