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Diffstat (limited to 'src/tools/clippy/src/docs/len_zero.txt')
-rw-r--r-- | src/tools/clippy/src/docs/len_zero.txt | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/src/tools/clippy/src/docs/len_zero.txt b/src/tools/clippy/src/docs/len_zero.txt new file mode 100644 index 000000000..664124bd3 --- /dev/null +++ b/src/tools/clippy/src/docs/len_zero.txt @@ -0,0 +1,28 @@ +### What it does +Checks for getting the length of something via `.len()` +just to compare to zero, and suggests using `.is_empty()` where applicable. + +### Why is this bad? +Some structures can answer `.is_empty()` much faster +than calculating their length. So it is good to get into the habit of using +`.is_empty()`, and having it is cheap. +Besides, it makes the intent clearer than a manual comparison in some contexts. + +### Example +``` +if x.len() == 0 { + .. +} +if y.len() != 0 { + .. +} +``` +instead use +``` +if x.is_empty() { + .. +} +if !y.is_empty() { + .. +} +```
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