+4

CHANGELOG.md

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··· 110 110 check in an `assert`. 111 111 ([Giacomo Cavalieri](https://github.com/giacomocavalieri)) 112 112 113 113 + - Fixed a bug where the compiler would generate invalid code on the JavaScript 114 114 + target for some `case` expressions using clause guards. 115 115 + ([Giacomo Cavalieri](https://github.com/giacomocavalieri)) 116 116 + 113 117 - The formatter no longer stack overflows trying to format lists with many 114 118 items. 115 119 ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

+44 -4

compiler-core/src/javascript/decision.rs

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··· 31 31 subjects: &'a [TypedExpr], 32 32 expression_generator: &mut Generator<'_, 'a>, 33 33 ) -> Document<'a> { 34 34 + let scope_position = expression_generator.scope_position.clone(); 34 35 let mut variables = Variables::new(expression_generator, VariableAssignment::Declare); 35 36 let assignments = variables.assign_case_subjects(compiled_case, subjects); 36 36 - let decision = CasePrinter { 37 37 + let mut printer = CasePrinter { 37 38 variables, 38 39 assignments: &assignments, 39 40 kind: DecisionKind::Case { clauses }, 40 40 - } 41 41 - .decision(&compiled_case.tree); 41 41 + }; 42 42 43 43 - docvec![assignments_to_doc(assignments), decision.into_doc()].force_break() 43 43 + let decision = match &compiled_case.tree { 44 44 + // Printing needs extra care if we're dealing with a sort of "degenerate" 45 45 + // tree that immediately starts with a guard node. 46 46 + // Code generation for guard nodes require defining variables outside of 47 47 + // the safe scope of the generated `if` statement. So if we were to just 48 48 + // generate code like usual we run the risk of leaking variables in the 49 49 + // outer scope: 50 50 + // 51 51 + // ```case 52 52 + // case 11 { 53 53 + // n if n == 10 -> todo 54 54 + // _ -> todo 55 55 + // } 56 56 + // 57 57 + // let n = 12 58 58 + // ``` 59 59 + // 60 60 + // That case would have us generate something like this: 61 61 + // 62 62 + // ```js 63 63 + // let n = 11 64 64 + // if (n === 10) { todo } else { todo } 65 65 + // 66 66 + // // If we don't wrap it in a block that `n = 11` definition that was 67 67 + // // introduced would end up clashing with the `let n = 12` that comes 68 68 + // // later! 69 69 + // ``` 70 70 + // 71 71 + // So in this special case we have to wrap everything in a block. 72 72 + tree @ Decision::Guard { .. } if !scope_position.is_tail() => break_block( 73 73 + printer 74 74 + .inside_new_scope(|this| this.decision(tree)) 75 75 + .into_doc(), 76 76 + ), 77 77 + 78 78 + tree @ Decision::Run { .. } 79 79 + | tree @ Decision::Guard { .. } 80 80 + | tree @ Decision::Switch { .. } 81 81 + | tree @ Decision::Fail => printer.decision(tree).into_doc(), 82 82 + }; 83 83 + docvec![assignments_to_doc(assignments), decision].force_break() 44 84 } 45 85 46 86 /// The generated code for a decision tree.

+35

compiler-core/src/javascript/tests/case.rs

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··· 887 887 "# 888 888 ) 889 889 } 890 890 + 891 891 + #[test] 892 892 + // https://github.com/gleam-lang/gleam/issues/5283 893 893 + fn duplicate_name_for_variables_used_in_guards() { 894 894 + assert_js!( 895 895 + r#" 896 896 + pub fn wibble() { 897 897 + let a = case 1337 { 898 898 + n if n == 1347 -> Nil 899 899 + _ -> Nil 900 900 + } 901 901 + let b = case 1337 { 902 902 + n -> Nil 903 903 + } 904 904 + }"# 905 905 + ) 906 906 + } 907 907 + 908 908 + #[test] 909 909 + // https://github.com/gleam-lang/gleam/issues/5283 910 910 + fn duplicate_name_for_variables_used_in_guards_shadowing_outer_name() { 911 911 + assert_js!( 912 912 + r#" 913 913 + pub fn wibble() { 914 914 + let n = 1 915 915 + let a = case 1337 { 916 916 + n if n == 1347 -> n 917 917 + _ -> n 918 918 + } 919 919 + let b = case 1337 { 920 920 + n -> Nil 921 921 + } 922 922 + }"# 923 923 + ) 924 924 + }

+36

compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__case__duplicate_name_for_variables_used_in_guards.snap

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··· 1 1 + --- 2 2 + source: compiler-core/src/javascript/tests/case.rs 3 3 + expression: "\npub fn wibble() {\n let a = case 1337 {\n n if n == 1347 -> Nil\n _ -> Nil\n }\n let b = case 1337 {\n n -> Nil\n }\n}" 4 4 + --- 5 5 + ----- SOURCE CODE 6 6 + 7 7 + pub fn wibble() { 8 8 + let a = case 1337 { 9 9 + n if n == 1347 -> Nil 10 10 + _ -> Nil 11 11 + } 12 12 + let b = case 1337 { 13 13 + n -> Nil 14 14 + } 15 15 + } 16 16 + 17 17 + ----- COMPILED JAVASCRIPT 18 18 + export function wibble() { 19 19 + let _block; 20 20 + let $ = 1337; 21 21 + { 22 22 + let n = $; 23 23 + if (n === 1347) { 24 24 + _block = undefined; 25 25 + } else { 26 26 + _block = undefined; 27 27 + } 28 28 + } 29 29 + let a = _block; 30 30 + let _block$1; 31 31 + let $1 = 1337; 32 32 + let n = $1; 33 33 + _block$1 = undefined; 34 34 + let b = _block$1; 35 35 + return b; 36 36 + }

+38

compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__case__duplicate_name_for_variables_used_in_guards_shadowing_outer_name.snap

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··· 1 1 + --- 2 2 + source: compiler-core/src/javascript/tests/case.rs 3 3 + expression: "\npub fn wibble() {\n let n = 1\n let a = case 1337 {\n n if n == 1347 -> n\n _ -> n\n }\n let b = case 1337 {\n n -> Nil\n }\n}" 4 4 + --- 5 5 + ----- SOURCE CODE 6 6 + 7 7 + pub fn wibble() { 8 8 + let n = 1 9 9 + let a = case 1337 { 10 10 + n if n == 1347 -> n 11 11 + _ -> n 12 12 + } 13 13 + let b = case 1337 { 14 14 + n -> Nil 15 15 + } 16 16 + } 17 17 + 18 18 + ----- COMPILED JAVASCRIPT 19 19 + export function wibble() { 20 20 + let n = 1; 21 21 + let _block; 22 22 + let $ = 1337; 23 23 + { 24 24 + let n$1 = $; 25 25 + if (n$1 === 1347) { 26 26 + _block = $; 27 27 + } else { 28 28 + _block = n; 29 29 + } 30 30 + } 31 31 + let a = _block; 32 32 + let _block$1; 33 33 + let $1 = 1337; 34 34 + let n$1 = $1; 35 35 + _block$1 = undefined; 36 36 + let b = _block$1; 37 37 + return b; 38 38 + }

+6 -4

compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__case__var_true.snap

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··· 28 28 let $ = 0; 29 29 let _block; 30 30 let $1 = undefined; 31 31 - if (true_) { 32 32 - _block = 0; 33 33 - } else { 34 34 - _block = 1; 31 31 + { 32 32 + if (true_) { 33 33 + _block = 0; 34 34 + } else { 35 35 + _block = 1; 36 36 + } 35 37 } 36 38 let $2 = _block; 37 39 if (!($ === $2)) {

+12

test/language/test/language/clause_guard_test.gleam

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··· 548 548 _ -> False 549 549 } 550 550 } 551 551 + 552 552 + // https://github.com/gleam-lang/gleam/issues/5283 553 553 + pub fn case_with_guard_does_not_pollute_outer_scope_test() { 554 554 + let a = case 1337 { 555 555 + n if n == 1347 -> 1 556 556 + _ -> 2 557 557 + } 558 558 + let b = case 1337 { 559 559 + n -> 2 560 560 + } 561 561 + assert a == b 562 562 + }