Module rustc_const_eval::interpret::validity

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Check the validity invariant of a given value, and tell the user where in the value it got violated. In const context, this goes even further and tries to approximate const safety. That’s useful because it means other passes (e.g. promotion) can rely on consts to be const-safe.


  • If $e throws an error matching the pattern, throw a validation failure. Other errors are passed back to the caller, unchanged – and if they reach the root of the visitor, we make sure only validation errors and InvalidProgram errors are left. This lets you use the patterns as a kind of validation list, asserting which errors can possibly happen:



  • Extra things to check for during validation of CTFE results.
  • We want to show a nice path to the invalid field for diagnostics, but avoid string operations in the happy case where no error happens. So we track a Vec<PathElem> where PathElem contains all the data we need to later print something for the user.


  • mutability 🔒
    Returns whether the allocation is mutable, and whether it’s actually a static. For “root” statics we look at the type to account for interior mutability; for nested statics we have no type and directly use the annotated mutability.
  • write_path 🔒
    Format a path