vosen/ZLUDA · error

Could not guess if ` ` is a read or write argument. Name…

Error message

Could not guess if `{}` is a read or write argument. Name should start with `dst` or `src`

What it means

The proc-macro infers whether an instruction argument is a destination (written) or source (read) purely from the field name prefix: names starting with `dst` are destinations, names starting with `src` are sources. `is_dst` throws this compile-time error for any argument name matching neither prefix, because the macro cannot decide which side of the instruction the operand belongs to.

Solutions

1. Rename the argument so it starts with `dst` for written operands (e.g. `dst`, `dst_addr`) or `src` for read operands (e.g. `src1`, `src_imm`)
2. Check existing instruction definitions in the codebase for the established naming pattern and follow it
3. If the name genuinely cannot start with dst/src, extend `is_dst` in ptx_parser_macros_impl/src/lib.rs:775 with an explicit mapping for the new name

Example fix

// before
arguments { out: Reg, addr: Mem } => ...
// after
arguments { dst: Reg, src_addr: Mem } => ...

// Pre-check argument names before feeding them to the macro:
fn valid_arg_name(name: &str) -> bool {
    name.starts_with("dst") || name.starts_with("src")
}

When it happens

Trigger: Declaring an instruction argument field named `out`, `addr`, `imm`, `result`, `reg1`, or any identifier not beginning with `dst` or `src` inside the `arguments` block of the DSL. Note case-sensitivity: `DST`/`Src` also fail since the check is on lowercase prefixes of the identifier text.

Common situations: Renaming fields for readability, porting instruction definitions from PTX docs that use different naming (`rd`, `rs1`), or writing new instruction definitions without knowing the naming convention.

Understand the failure class

Background: "invalid id" errors: invalid identifier format — why libraries reject IDs before lookup, and how to fix them — this error's family across 37 libraries.

Related errors

• Unexpected key ` `, expected `repr` or `space
• Unexpected key ` `. Expected `type`, `data`, `arguments`…
• io::Error::new(io::ErrorKind::InvalidData, e.to_string())

AI-assisted analysis of vosen/ZLUDA@9c8b43f242 (2026-09-06). Data as JSON: /api/errors/aa4116083948a27e. Report an issue: GitHub.

Appendix: source

Thrown at ptx_parser_macros_impl/src/lib.rs:779

            quote! {
                MapOperand::map(arguments.#name, |x| visitor.visit(x, type_space, #is_dst, #relaxed_type_check))?
            }
        };
        quote! {
            let #name = {
                #type_space
                #map_call
            };
        }
    }

    fn is_dst(name: &Ident) -> syn::Result<bool> {
        if name.to_string().starts_with("dst") {
            Ok(true)
        } else if name.to_string().starts_with("src") {
            Ok(false)
        } else {
            return Err(syn::Error::new(
                name.span(),
                format!(
                    "Could not guess if `{}` is a read or write argument. Name should start with `dst` or `src`",
                    name
                ),
            ));
        }
    }

    fn emit_field(&self, vis: &Option<Visibility>) -> TokenStream {
        let name = &self.name;
        let type_ = &self.repr;
        quote! {
            #vis #name: #type_
        }
    }
}

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