TOB-FUEL-33: Decoding of TxPointer with multibyte characters might panic

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Description

The decoding of a TxPointer might panic if the input string contains multi-byte characters. The following code shows a unit test which panics.

Figure 33.1: Unit test that panics.

#[test]
fn panic_slice() {
TxPointer::from_str(&"0000000 0").expect("failed to decode from str"); 😎
}

The next figure highlights the string-slice operation which causes the panic.

Figure 33.2: Decoding function from strings to TxPointer. (fuel-vm/fuel-tx/src/tx_pointer.rs/#92–107)

impl str::FromStr for TxPointer {
    type Err = &'static str;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        const ERR: &str = "Invalid encoded byte";
        if s.len() != 12 {
            return Err(ERR)
        }
        let block_height = u32::from_str_radix(
        let tx_index = u16::from_str_radix(&
        Ok(Self::new(block_height.into(), tx_index))
    }
}

Recommendations

Short term, verify that the input for the TxPointer parsing function contains only single byte characters.
Long term, consider enabling the Clippy rule string_slice.

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Fixed with https://github.com/FuelLabs/fuel-vm/pull/531/files#diff-5e8f20ef505c4bf05907fd891dd939ef37cf9f38c9677fc058552867b0f1e166