Add support for postfix yield expressions

We had a discussion[1] today about whether postfix yield would make sense.
It's easy enough to support both in the parser, so we might as well have
both and see how people use it while the feature is experimental.

[1]: https://rust-lang.zulipchat.com/#narrow/channel/481571-t-lang.2Fgen/topic/postfix-yield/with/505231568

1 files changed, 7 insertions, 0 deletions

diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 9b2d562a69e..1df6283af26 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -1310,6 +1310,13 @@ impl<'a> Parser<'a> {
             return self.parse_match_block(lo, match_span, self_arg, MatchKind::Postfix);
         }
 
+        // Post-fix yield
+        if self.eat_keyword(exp!(Yield)) {
+            let yield_span = self.prev_token.span;
+            self.psess.gated_spans.gate(sym::yield_expr, yield_span);
+            return Ok(self.mk_expr(yield_span, ExprKind::Yield(Some(self_arg))));
+        }
+
         let fn_span_lo = self.token.span;
         let mut seg = self.parse_path_segment(PathStyle::Expr, None)?;
         self.check_trailing_angle_brackets(&seg, &[exp!(OpenParen)]);