MGS1051: a spell does not match the spell contract

magus refuses to load a spell when one of its exported mgs_ functions does not match the spell contract:

• it declares a return type other than the contract's, > any included;
• it declares no return type;
• it takes parameters;
• its name is not a contract function, such as a misspelling or a function the contract no longer has.

magus reads each function's return annotation from the spell's source before it calls any of them, on every load. The error lists every violation with its line.

Why

magus decodes each mgs_ value into the type the contract names. The Buzz checker checks a function body against its own annotation, but nothing else checks that annotation against the contract, so a spell declaring > any hands magus a value whose shape nothing checked. A function the contract does not list is a declaration magus would silently ignore.

Resolution

• Declare the contract's return type. The spell contract lists each function's exact annotation, for example export fun mgs_getLanguage() > Language.
• Return one shape per function. A > any that mixes commands and services splits into mgs_listTargets and mgs_listServices.
• Rename or remove an unknown function. Fix a misspelling; delete a function the contract dropped.