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Merge #93

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93: Support leading pipe in match arms r=matklad a=DJMcNab

This adds support for match arms of the form:
```rust
<...>
| X | Y => <...>,
| X => <...>,
| 1..2 => <...>,
etc
```

# Implementation discussion

This just naïvely 'eats' a leading pipe if one is available. The equivalent line in the reference `libsyntax` is in [`parse_arm`](441519536c/src/libsyntax/parse/parser.rs (L3552)).

As noted in the comment linked above, this feature was formally introduced as a result of rust-lang/rfcs#1925. This feature is in active use in the [`rust-analyzer` codebase](c87fcb4ea5/crates/ra_syntax/src/syntax_kinds/generated.rs (L231))

I have added some tests for this feature, but maybe more would be required

EDIT: Always looking for feedback - is this PR description over-engineered?

Co-authored-by: Daniel McNab <36049421+djmcnab@users.noreply.github.com>
This commit is contained in:
bors[bot] 2018-10-04 07:02:19 +00:00
commit 7a025ad201
3 changed files with 59 additions and 12 deletions
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3
crates/ra_syntax/src/grammar/expressions/atom.rs
View file

@ -319,10 +319,13 @@ pub(crate) fn match_arm_list(p: &mut Parser) {
// match () {
// _ => (),
// X | Y if Z => (),
// | X | Y if Z => (),
// | X => (),
// };
// }
fn match_arm(p: &mut Parser) -> BlockLike {
let m = p.start();
p.eat(PIPE);
patterns::pattern_r(p, TokenSet::EMPTY);
while p.eat(PIPE) {
patterns::pattern(p);

2
crates/ra_syntax/tests/data/parser/inline/0069_match_arm.rs
View file

@ -2,5 +2,7 @@ fn foo() {
match () {
_ => (),
X | Y if Z => (),
| X | Y if Z => (),
| X => (),
};
}

66
crates/ra_syntax/tests/data/parser/inline/0069_match_arm.txt
View file

@ -1,5 +1,5 @@
ROOT@[0; 78)
FN_DEF@[0; 77)
ROOT@[0; 125)
FN_DEF@[0; 124)
FN_KW@[0; 2)
WHITESPACE@[2; 3)
NAME@[3; 6)
@ -8,18 +8,18 @@ ROOT@[0; 78)
L_PAREN@[6; 7)
R_PAREN@[7; 8)
WHITESPACE@[8; 9)
BLOCK@[9; 77)
BLOCK@[9; 124)
L_CURLY@[9; 10)
WHITESPACE@[10; 15)
EXPR_STMT@[15; 75)
MATCH_EXPR@[15; 74)
EXPR_STMT@[15; 122)
MATCH_EXPR@[15; 121)
MATCH_KW@[15; 20)
WHITESPACE@[20; 21)
TUPLE_EXPR@[21; 23)
L_PAREN@[21; 22)
R_PAREN@[22; 23)
WHITESPACE@[23; 24)
MATCH_ARM_LIST@[24; 74)
MATCH_ARM_LIST@[24; 121)
L_CURLY@[24; 25)
WHITESPACE@[25; 34)
MATCH_ARM@[34; 41)
@ -58,9 +58,51 @@ ROOT@[0; 78)
L_PAREN@[65; 66)
R_PAREN@[66; 67)
COMMA@[67; 68)
WHITESPACE@[68; 73)
R_CURLY@[73; 74)
SEMI@[74; 75)
WHITESPACE@[75; 76)
R_CURLY@[76; 77)
WHITESPACE@[77; 78)
WHITESPACE@[68; 77)
MATCH_ARM@[77; 95)
PIPE@[77; 78)
WHITESPACE@[78; 79)
BIND_PAT@[79; 80)
NAME@[79; 80)
IDENT@[79; 80) "X"
WHITESPACE@[80; 81)
PIPE@[81; 82)
WHITESPACE@[82; 83)
BIND_PAT@[83; 84)
NAME@[83; 84)
IDENT@[83; 84) "Y"
WHITESPACE@[84; 85)
IF_KW@[85; 87)
WHITESPACE@[87; 88)
PATH_EXPR@[88; 89)
PATH@[88; 89)
PATH_SEGMENT@[88; 89)
NAME_REF@[88; 89)
IDENT@[88; 89) "Z"
WHITESPACE@[89; 90)
FAT_ARROW@[90; 92)
WHITESPACE@[92; 93)
TUPLE_EXPR@[93; 95)
L_PAREN@[93; 94)
R_PAREN@[94; 95)
COMMA@[95; 96)
WHITESPACE@[96; 105)
MATCH_ARM@[105; 114)
PIPE@[105; 106)
WHITESPACE@[106; 107)
BIND_PAT@[107; 108)
NAME@[107; 108)
IDENT@[107; 108) "X"
WHITESPACE@[108; 109)
FAT_ARROW@[109; 111)
WHITESPACE@[111; 112)
TUPLE_EXPR@[112; 114)
L_PAREN@[112; 113)
R_PAREN@[113; 114)
COMMA@[114; 115)
WHITESPACE@[115; 120)
R_CURLY@[120; 121)
SEMI@[121; 122)
WHITESPACE@[122; 123)
R_CURLY@[123; 124)
WHITESPACE@[124; 125)