1951: Lower the precedence of the `as` operator. r=matklad a=goffrie
Previously, the `as` operator was being parsed like a postfix expression, and
therefore being given the highest possible precedence. That caused it to bind
more tightly than prefix operators, which it should not. Instead, parse it
somewhat like a normal binary expression with some special-casing.
Fixes#1851.
Co-authored-by: Geoffry Song <goffrie@gmail.com>
Forbidding block expressions entirely is too strict; instead, we should only
forbid them in contexts where we are parsing an optional RHS (i.e. the RHS of a
range expression).
Previously, the `as` operator was being parsed like a postfix expression, and
therefore being given the highest possible precedence. That caused it to bind
more tightly than prefix operators, which it should not. Instead, parse it
somewhat like a normal binary expression with some special-casing.
1848: Parse `..` as a full pattern r=matklad a=ecstatic-morse
Resolves#1479.
This PR implements [RFC 2707](https://github.com/rust-lang/rfcs/pull/2707) in the parser. It introduces a new `DotDotPat` AST node modeled on `PlaceholderPat` and changes the parsing of tuple and slice patterns to conform to the RFC.
Notably, this PR does *not* change the resulting AST when `..` appears in a struct pattern (e.g. `Struct { a, b: c, .. }`). I *think* this is the behavior mandated by RFC 2707, but someone should confirm this.
Co-authored-by: Dylan MacKenzie <ecstaticmorse@gmail.com>
Parser has the invariant that `{}` are balanced.
Previous code tried (unsucesfuly) maintain the same invariant for
`$()` as well, but it was done in a rather ad-hoc manner: it's not at
all obvious that it is possible to maintain both invariants!
Named structs can have `box` patterns that will bind to their fields.
This is similar to the behavior of the `ref` and `mut` fields, but is at
least a little bit surprising.
