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| -rw-r--r-- | src/doc/trpl/patterns.md | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/src/doc/trpl/patterns.md b/src/doc/trpl/patterns.md index 3d22066c725..8f4a7a43955 100644 --- a/src/doc/trpl/patterns.md +++ b/src/doc/trpl/patterns.md @@ -23,6 +23,31 @@ match x { This prints `one`. +There’s one pitfall with patterns: like anything that introduces a new binding, +they introduce shadowing. For example: + +```rust +let x = 'x'; +let c = 'c'; + +match c { + x => println!("x: {} c: {}", x, c), +} + +println!("x: {}", x) +``` + +This prints: + +```text +x: c c: c +x: x +``` + +In other words, `x =>` matches the pattern and introduces a new binding named +`x` that’s in scope for the match arm. Because we already have a binding named +`x`, this new `x` shadows it. + # Multiple patterns You can match multiple patterns with `|`: |