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Fix grammar for LiteralPattern regarding - #1824

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May 15, 2025
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Fix grammar for LiteralPattern regarding - #1824

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16 changes: 2 additions & 14 deletions src/patterns.md
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Original file line number Diff line number Diff line change
Expand Up @@ -139,23 +139,11 @@ r[patterns.literal]

r[patterns.literal.syntax]
```grammar,patterns
LiteralPattern ->
`true` | `false`
| CHAR_LITERAL
| BYTE_LITERAL
| STRING_LITERAL
| RAW_STRING_LITERAL
| BYTE_STRING_LITERAL
| RAW_BYTE_STRING_LITERAL
| C_STRING_LITERAL
| RAW_C_STRING_LITERAL
| `-`? INTEGER_LITERAL
| `-`? FLOAT_LITERAL
LiteralPattern -> `-`? LiteralExpression
```

r[patterns.literal.intro]
_Literal patterns_ match exactly the same value as what is created by the literal.
Since negative numbers are not [literals], literal patterns also accept an optional minus sign before the literal, which acts like the negation operator.
_Literal patterns_ match exactly the same value as what is created by the literal. Since negative numbers are not [literals], literals in patterns may be prefixed by an optional minus sign, which acts like the negation operator.
Comment on lines -157 to +146
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I reworded this a bit, as it seemed to be saying two conflicting things. On the one hand, "literal patterns" match exactly what's parsed as a literal. But on the other, it said that "literal patterns" accept a minus sign, which isn't part of the literal. It seems better to just say that literals in patterns may be prefixed by an optional minus sign.


> [!WARNING]
> C string and raw C string literals are accepted in literal patterns, but `&CStr` doesn't implement structural equality (`#[derive(Eq, PartialEq)]`) and therefore any such `match` on a `&CStr` will be rejected with a type error.
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