demangle.go
func (st *state) templateParam() AST {
	if len(st.templates) == 0 {
		st.fail("template parameter not in scope of template")
	}
	off := st.off

	st.checkChar('T')
	n := st.compactNumber()

	template := st.templates[len(st.templates)-1]

	if template == nil {
		// We are parsing a cast operator.  If the cast is
		// itself a template, then this is a forward
		// reference.  Fill it in later.
		return &TemplateParam{Index: n, Template: nil}
	}

	if n >= len(template.Args) {
		st.failEarlier(fmt.Sprintf("template index out of range (%d >= %d)", n, len(template.Args)), st.off-off)
	}

	return &TemplateParam{Index: n, Template: template}
}
func (st *state) templateParam() AST {
	if len(st.templates) == 0 {
		st.fail("template parameter not in scope of template")
	}
	off := st.off

	st.checkChar('T')
	n := st.compactNumber()

	template := st.templates[len(st.templates)-1]

	if template == nil {
		// We are parsing a cast operator.  If the cast is
		// itself a template, then this is a forward
		// reference.  Fill it in later.
		return &TemplateParam{Index: n, Template: nil}
	}

	if n >= len(template.Args) {
		st.failEarlier(fmt.Sprintf("template index out of range (%d >= %d)", n, len(template.Args)), st.off-off)
	}

	return &TemplateParam{Index: n, Template: template}
}
func ( st * state ) templateParam ( ) AST { if len ( st . templates ) == 0 { st . fail ( " " ) } off := st . off st . checkChar ( 'T' ) n := st . compactNumber ( ) template := st . templates [ len ( st . templates ) - 1 ] if template == nil { // We are parsing a cast operator.  If the cast is // itself a template, then this is a forward // reference.  Fill it in later. return & TemplateParam { Index : n , Template : nil } } if n >= len ( template . Args ) { st . failEarlier ( fmt . Sprintf ( " " , n , len ( template . Args ) ) , st . off - off ) } return & TemplateParam { Index : n , Template : template } }
// <template-param> ::= T_
//                  ::= T <(parameter-2 non-negative) number> _
//
// When a template parameter is a substitution candidate, any
// reference to that substitution refers to the template parameter
// with the same index in the currently active template, not to
// whatever the template parameter would be expanded to here.  We sort
// this out in substitution and simplify.
<template - param > :: = T_ :: = T < ( parameter - 2 non - negative ) number > _ When a template parameter is a substitution candidate any reference to that substitution refers to the template parameter with the same index in the currently active template not to whatever the template parameter would be expanded to here . We sort this out in substitution and simplify .