vosen/ZLUDA · error

Could not guess if `{}` is a read or write argument. Name sh

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.

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_
        }
    }
}

View on GitHub (pinned to 9c8b43f242)

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 `type`, `data`, `arguments`, `
• Unexpected key `{}`, expected `repr` or `space
• 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.