[Bug]: Reverts in Nested Contract Calls Should Be Handled Gracefully

[0xNeshi]

What happened?

Currently the panic unwinds. This causes problems in unit tests for SafeErc20, copy/paste the following code into contracts/src/token/erc20/utils/safe_erc20.rs > tests:

    // Mock ERC20-like contract that panics on `allowance` calls
    #[storage]
    struct PanickingAllowanceToken;

    unsafe impl TopLevelStorage for PanickingAllowanceToken {}

    #[public]
    impl PanickingAllowanceToken {
        // External signature matches IERC20.allowance(owner, spender) ->
        // uint256 Panicking causes a revert so the RawCall in
        // SafeErc20::allowance fails.
        fn allowance(&self, _owner: Address, _spender: Address) -> U256 {
            panic!("revert");
        }
    }

    // When the token's allowance call reverts, SafeErc20::allowance should map
    // it to Error::SafeErc20FailedOperation and bubble up through callers
    // like safe_increase_allowance.
    #[motsu::test]
    fn safe_increase_allowance_reverts_on_allowance_call_panic(
        contract: Contract<SafeErc20Example>,
        bad_token: Contract<PanickingAllowanceToken>,
        alice: Address,
    ) {
        let token = bad_token.address();
        let err = contract
            .sender(alice)
            .safe_increase_allowance(token, alice, U256::from(1))
            .unwrap_err();
        assert!(
            matches!(err, Error::SafeErc20FailedOperation(SafeErc20FailedOperation { token }) if token == bad_token.address())
        );
    }

Running this tests results in:

thread 'token::erc20::utils::safe_erc20::tests::safe_increase_allowance_reverts_on_allowance_call_error' panicked at library/core/src/panicking.rs:225:5:
panic in a function that cannot unwind
stack backtrace:
   0:     0x62314773ef82 - std::backtrace_rs::backtrace::libunwind::trace::hf0b950c5fb8c6b8c
                               at /rustc/5d707b07e42766c080c5012869c9988a18dcbb83/library/std/src/../../backtrace/src/backtrace/libunwind.rs:117:9
   1:     0x62314773ef82 - std::backtrace_rs::backtrace::trace_unsynchronized::hbababaa4234eb23f
   ...

platform

• linux
• windows
• macos

Expected behavior

The test case above should successfully pass without unwinding panics.

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