Fix grammar for RangePatternBound regarding literals
#1825
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The compiler, in parsing, accepts many more kinds of literals in the
bound of a range pattern than what we had documented, and as with
`PatternWithoutRange`, the parser allows each of these literals to be
prefixed with `-`. E.g.
```rust
#[cfg(any())]
match () {
..-true | ..-false => (),
..-'x' => (),
..-b'x' => (),
..-"x" => (),
..-r"x" => (),
..-br"x" => (),
..-c"x" => (),
..-cr"x" => (),
..-1 => (),
..-1.1 => (),
}
```
Let's fix this by adjusting the `RangePatternBound` production to use
`LiteralPattern`. In a separate PR, we've adjusted `LiteralPattern`
to allow for a minus sign ahead of all literal expressions.
To help the reader, let's also add a note that highlights that what we
discuss later as being allowed semantically is more restrictive than
what we allow in parsing (and therefore in the grammar).
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The compiler, in parsing, accepts many more kinds of literals in the bound of a range pattern than what we had documented, and as with
PatternWithoutRange, the parser allows each of these literals to be prefixed with-. E.g.Let's fix this by adjusting the
RangePatternBoundproduction to useLiteralPattern. In a separate PR, we've adjustedLiteralPatternto allow for a minus sign ahead of all literal expressions.To help the reader, let's also add a note that highlights that what we discuss later as being allowed semantically is more restrictive than what we allow in parsing (and therefore in the grammar).
cc @ehuss