allow pattern matching on discard in case branches · nandi.uk/gleam@1ec479c

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CHANGELOG.md

··· 18 18 ``` 19 19 20 20 The compiler will display this error message: 21 + 21 22 ```text 22 23 error: Unknown variable 23 24 ┌─ /path/to/project/src/project.gleam:4:3 ··· 192 193 193 194 - The language server now presents quick fix code actions before refactoring 194 195 ones. 196 + ([Giacomo Cavalieri](https://github.com/giacomocavalieri)) 197 + 198 + - The language server now allows to further pattern match on a discard by 199 + replacing it with the patterns it is discarding. 200 + For example: 201 + 202 + ```gleam 203 + pub fn list_names(x: Result(List(String), Nil)) { 204 + case x { 205 + Error(Nil) -> io.println("no names") 206 + Ok(_) -> todo 207 + // ^ Triggering the code action here 208 + } 209 + } 210 + ``` 211 + 212 + Triggering the code action will result in the following code: 213 + 214 + ```gleam 215 + pub fn list_names(x: Result(List(String), Nil)) { 216 + case x { 217 + Error(Nil) -> io.println("no names") 218 + Ok([]) -> todo 219 + Ok([first, ..rest]) -> todo 220 + } 221 + } 222 + ``` 223 + 195 224 ([Giacomo Cavalieri](https://github.com/giacomocavalieri)) 196 225 197 226 - The language server no longer shows completions for deprecated values from

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language-server/src/code_action.rs

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··· 5522 5522 /// This location covers the entire list tail pattern, including the `..` 5523 5523 location: SrcSpan, 5524 5524 }, 5525 + /// When the pattern being matched is a discard. For example: 5526 + /// ```gleam 5527 + /// case wibble { 5528 + /// Ok(_) -> todo 5529 + /// // ^ Hovering this! 5530 + /// } 5531 + /// ``` 5532 + Discard { location: SrcSpan }, 5525 5533 } 5526 5534 5527 5535 impl PatternLocation { 5528 5536 fn regular(location: SrcSpan) -> Self { 5529 5537 Self::Regular { location } 5538 + } 5539 + 5540 + fn is_discard(&self) -> bool { 5541 + match self { 5542 + PatternLocation::Regular { .. } | PatternLocation::ListTail { .. } => false, 5543 + PatternLocation::Discard { .. } => true, 5544 + } 5530 5545 } 5531 5546 } 5532 5547 ··· 5581 5596 clause_location, 5582 5597 bound_variables, 5583 5598 }) => { 5599 + let title = if variable_location.is_discard() { 5600 + "Pattern match on value" 5601 + } else { 5602 + "Pattern match on variable" 5603 + }; 5604 + 5584 5605 self.match_on_clause_variable( 5585 5606 variable_type, 5586 5607 variable_location, 5587 5608 clause_location, 5588 5609 &bound_variables, 5589 5610 ); 5590 - "Pattern match on variable" 5611 + 5612 + title 5591 5613 } 5592 5614 5593 5615 None => return vec![], ··· 5739 5761 let nesting = " ".repeat(clause_range.start.character as usize); 5740 5762 5741 5763 let variable_location = match variable_location { 5742 - PatternLocation::Regular { location } => location, 5743 - PatternLocation::ListTail { location } => location, 5764 + PatternLocation::Regular { location } 5765 + | PatternLocation::ListTail { location } 5766 + | PatternLocation::Discard { location } => location, 5744 5767 }; 5745 5768 5746 5769 let variable_start = (variable_location.start - clause_location.start) as usize; ··· 6109 6132 } 6110 6133 6111 6134 ast::visit::visit_typed_use(self, use_); 6135 + } 6136 + 6137 + fn visit_typed_pattern_discard( 6138 + &mut self, 6139 + location: &'ast SrcSpan, 6140 + name: &'ast EcoString, 6141 + type_: &'ast Arc<Type>, 6142 + ) { 6143 + if within( 6144 + self.params.range, 6145 + self.edits.src_span_to_lsp_range(*location), 6146 + ) { 6147 + let location = PatternLocation::Discard { 6148 + location: *location, 6149 + }; 6150 + self.pattern_variable_under_cursor = Some((name, location, type_.clone())); 6151 + } 6112 6152 } 6113 6153 6114 6154 fn visit_typed_pattern_variable(

+42

language-server/src/tests/action.rs

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··· 179 179 const GENERATE_TO_JSON_FUNCTION: &str = "Generate to-JSON function"; 180 180 const PATTERN_MATCH_ON_ARGUMENT: &str = "Pattern match on argument"; 181 181 const PATTERN_MATCH_ON_VARIABLE: &str = "Pattern match on variable"; 182 + const PATTERN_MATCH_ON_VALUE: &str = "Pattern match on value"; 182 183 const GENERATE_FUNCTION: &str = "Generate function"; 183 184 const CONVERT_TO_FUNCTION_CALL: &str = "Convert to function call"; 184 185 const INLINE_VARIABLE: &str = "Inline variable"; ··· 10827 10828 } 10828 10829 }", 10829 10830 find_position_of("else_").to_selection() 10831 + ); 10832 + } 10833 + 10834 + #[test] 10835 + fn pattern_match_on_discard_pattern_in_branch() { 10836 + assert_code_action!( 10837 + PATTERN_MATCH_ON_VALUE, 10838 + "pub fn main(x: Result(List(a), Nil)) { 10839 + case x { 10840 + Error(Nil) -> todo 10841 + Ok(_) -> todo 10842 + } 10843 + }", 10844 + find_position_of("_").to_selection() 10845 + ); 10846 + } 10847 + 10848 + #[test] 10849 + fn cannot_pattern_match_on_discard_on_the_left_of_an_assignment() { 10850 + assert_no_code_actions!( 10851 + PATTERN_MATCH_ON_VALUE, 10852 + "pub fn main(x: Result(List(a), Nil)) { 10853 + let _ = x 10854 + }", 10855 + find_position_of("_").to_selection() 10856 + ); 10857 + } 10858 + 10859 + #[test] 10860 + fn cannot_pattern_match_on_discard_on_the_left_of_a_use() { 10861 + assert_no_code_actions!( 10862 + PATTERN_MATCH_ON_VALUE, 10863 + "pub fn main() { 10864 + use _ <- wibble() 10865 + } 10866 + 10867 + fn wibble(fun: fn(Result(Int, Nil)) -> Nil) { 10868 + todo 10869 + } 10870 + ", 10871 + find_position_of("_").to_selection() 10830 10872 ); 10831 10873 } 10832 10874

+22

language-server/src/tests/snapshots/gleam_language_server__tests__action__pattern_match_on_discard_pattern_in_branch.snap

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··· 1 + --- 2 + source: language-server/src/tests/action.rs 3 + expression: "pub fn main(x: Result(List(a), Nil)) {\n case x {\n Error(Nil) -> todo\n Ok(_) -> todo\n }\n}" 4 + --- 5 + ----- BEFORE ACTION 6 + pub fn main(x: Result(List(a), Nil)) { 7 + case x { 8 + Error(Nil) -> todo 9 + Ok(_) -> todo 10 + ↑ 11 + } 12 + } 13 + 14 + 15 + ----- AFTER ACTION 16 + pub fn main(x: Result(List(a), Nil)) { 17 + case x { 18 + Error(Nil) -> todo 19 + Ok([]) -> todo 20 + Ok([first, ..rest]) -> todo 21 + } 22 + }

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