Fix check_cast harness #86
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tautschnig
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Sep 17, 2024
feliperodri
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Sep 18, 2024
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Sep 18, 2024
Kani enforces that `[kani::proof]` attribute is not applied to generic functions. We do not currently enforce this restriction on contract harnesses. When the compiler [searches for harnesses to verify](https://github.com/model-checking/kani/blob/dba8f3926a61025f5078de787ebd8d21278333ca/kani-compiler/src/kani_middle/codegen_units.rs#L63), it only looks at monomorphized functions. Thus, currently a user can write this code: ```rust #[kani::requires(true)] fn foo() {} #[kani::proof_for_contract(foo)] fn check_foo<T>() { foo() } ``` and get "No proof harnesses (functions with #[kani::proof]) were found to verify." In the case where a user is running many harnesses, they may not notice that Kani skipped the harness. For example, we currently have [this harness](https://github.com/model-checking/verify-rust-std/blob/149f6dd5409fac01a983d7b98c51d51666c74e45/library/core/src/ptr/unique.rs#L288) in the standard library, which doesn't actually run. (PR to fix is [here](model-checking/verify-rust-std#86)). After this PR merges, the code snippet above would instead error with: ```rust error: the '#[kani::proof_for_contract]' attribute cannot be applied to generic functions --> src/lib.rs:4:1 | 4 | #[kani::proof_for_contract(foo)] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: this error originates in the attribute macro `kani::proof_for_contract` (in Nightly builds, run with -Z macro-backtrace for more info) error: aborting due to 1 previous error ``` By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT licenses.
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Modifies the
check_castharness to:Currently, Kani doesn't run this harness. (See the log from a recent PR). It doesn't run the harness because it has a generic type parameter, and Kani's error handling for contract proofs doesn't check for this condition. (PR to fix is here). Once we remove the generic type parameter so that the harness runs, Kani complains that we can't run it as a proof for contract because there are no contracts, so we make it a regular proof instead.
By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT licenses.