E0308 rust type_error ai_generated true

error[E0308]: mismatched types: expected `usize`, found `u32`

ID: rust/e0308-expected-usize-found-u32

Also available as: JSON · Markdown · 中文
90%Fix Rate
83%Confidence
1Evidence
2023-03-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.65 active — — —
1.70 active — — —
1.75 active — — —

Root Cause

Using a fixed-size integer (like u32) where a usize is required, typically in array indexing or slice operations.

generic

中文

在需要 usize 的地方（如数组索引或切片操作）使用了固定大小整数（如 u32）。

Official Documentation

https://doc.rust-lang.org/error-index.html#E0308

Workarounds

  1. 95% success Convert explicitly with `try_into()`: `let idx: usize = index.try_into().unwrap();` 
    Convert explicitly with `try_into()`: `let idx: usize = index.try_into().unwrap();`
  2. 85% success Use `as` conversion if the value is guaranteed to fit: `let idx = index as usize;` 
    Use `as` conversion if the value is guaranteed to fit: `let idx = index as usize;`
  3. 90% success Change the function signature to accept usize: `fn process(index: usize)` 
    Change the function signature to accept usize: `fn process(index: usize)`

中文步骤

  1. Convert explicitly with `try_into()`: `let idx: usize = index.try_into().unwrap();`
  2. Use `as` conversion if the value is guaranteed to fit: `let idx = index as usize;`
  3. Change the function signature to accept usize: `fn process(index: usize)`

Dead Ends

Common approaches that don't work:

  1. Casting with `as`: `index as usize` without checking for overflow on 32-bit platforms 60% fail

    This works syntactically but may cause silent truncation on 32-bit systems if the u32 value exceeds 2^32.

  2. Changing the variable type to usize everywhere 70% fail

    May break other code that expects u32, and does not address the root cause of type mismatch.