param: IndexPopulated if there is exactly 1 parameter. Otherwise there are 0 parameters.
align_expr: IndexPopulated if align(A) is present.
addrspace_expr: IndexPopulated if addrspace(A) is present.
section_expr: IndexPopulated if linksection(A) is present.
callconv_expr: IndexPopulated if callconv(A) is present.
pub const FnProtoOne = struct {
/// Populated if there is exactly 1 parameter. Otherwise there are 0 parameters.
param: 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,
}