pub const FnProto = struct {
params_start: Index,
params_end: Index,
/// Populated if align(A) is present.
align_expr: Index,
/// Populated if addrspace(A) is present.
addrspace_expr: Index,
/// Populated if linksection(A) is present.
section_expr: Index,
/// Populated if callconv(A) is present.
callconv_expr: Index,
}