nandi.uk
Fork of daniellemaywood.uk/gleam — Wasm codegen work
Collapse `else if` in decision tree generation
author
GearsDatapacks
committer
Louis Pilfold
date
(May 14, 2025, 1:30 PM +0100)
commit
0d17d409
0d17d409b6dc2231ed658714d0a972da4cf27fef
parent
ce36223c
ce36223c0a6dd1b19f40324c304cc91427707f09
+192
-83
+51
-14
compiler-core/src/javascript/decision.rs
+51
-14
compiler-core/src/javascript/decision.rs
···
39
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let mut variables = Variables::new(expression_generator);
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let assignments = variables.assign_case_subjects(compiled_case, subjects)?;
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let decision = CasePrinter { clauses, variables }.decision(&compiled_case.tree)?;
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-
Ok(docvec![assignments_to_doc(assignments), decision].force_break())
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+
Ok(docvec![assignments_to_doc(assignments), decision.into_doc()].force_break())
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+
}
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+
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+
enum CaseBody<'a> {
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+
If(Document<'a>),
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+
Statements(Document<'a>),
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+
}
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+
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+
impl<'a> CaseBody<'a> {
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+
fn into_doc(self) -> Document<'a> {
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+
match self {
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CaseBody::If(document) | CaseBody::Statements(document) => document,
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+
}
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+
}
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}
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struct CasePrinter<'module, 'generator, 'a> {
···
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///
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/// So, as we're generating code for each check and move further down the decision
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/// tree, we will have to keep track of all the variables that we've discovered
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-
/// after each successfull check.
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+
/// after each successful check.
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///
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/// In order to do that we'll be using a `Variables` data structure to hold all
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/// this information about the current scope. This also allows us to reuse a lot
···
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/// the decision tree of let expressions!
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///
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impl<'a> CasePrinter<'_, '_, 'a> {
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-
fn decision(&mut self, decision: &'a Decision) -> Output<'a> {
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+
fn decision(&mut self, decision: &'a Decision) -> Result<CaseBody<'a>, Error> {
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match decision {
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Decision::Fail => unreachable!("Invalid decision tree reached code generation"),
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Decision::Run { body } => {
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let bindings = self.variables.bindings_doc(&body.bindings);
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let body = self.body_expression(body.clause_index)?;
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-
Ok(join_with_line(bindings, body))
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+
Ok(CaseBody::Statements(join_with_line(bindings, body)))
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}
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Decision::Switch {
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var,
···
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choices: &'a [(RuntimeCheck, Box<Decision>)],
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fallback: &'a Decision,
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fallback_check: &'a FallbackCheck,
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-
) -> Output<'a> {
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+
) -> Result<CaseBody<'a>, Error> {
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// If there's just a single choice we can just generate the code for
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// it: no need to do any checking, we know it must match!
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if choices.is_empty() {
···
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} else {
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docvec![" else if (", check_doc, ") "]
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};
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if_ = if_.append(docvec![branch, break_block(body?)]);
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+
if_ = if_.append(docvec![branch, break_block(body?.into_doc())]);
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}
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// In case there's some new variables we can extract after the
···
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}
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let body = self.inside_new_scope(|this| this.decision(fallback))?;
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+
let (body, wrap_body_in_block) = match body {
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CaseBody::If(document) => (document, false),
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+
CaseBody::Statements(document) => (document, true),
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+
};
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+
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+
let has_assignments = !assignments.is_empty();
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+
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let if_ = join_with_line(join(assignments, line()), if_);
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-
Ok(if body.is_empty() {
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+
let document = if body.is_empty() {
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if_
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-
} else {
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+
} else if wrap_body_in_block {
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docvec![if_, " else ", break_block(body)]
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+
} else {
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+
docvec![if_, " else ", body]
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+
};
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+
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+
Ok(if has_assignments {
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+
CaseBody::Statements(document)
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+
} else {
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+
CaseBody::If(document)
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})
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}
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···
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guard: usize,
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if_true: &'a Body,
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if_false: &'a Decision,
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-
) -> Output<'a> {
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+
) -> Result<CaseBody<'a>, Error> {
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let guard = self
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.clauses
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.get(guard)
···
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let if_true_body = this.body_expression(if_true.clause_index)?;
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Ok(join_with_line(if_true_bindings, if_true_body))
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})?;
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-
let if_false = self.inside_new_scope(|this| this.decision(if_false))?;
303
+
let if_false = self
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+
.inside_new_scope(|this| this.decision(if_false))?
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+
.into_doc();
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// We can now piece everything together into a single document!
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let if_ = docvec!["if (", check, ") ", break_block(if_true)];
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+
let has_assignments = !check_bindings.is_empty();
310
+
279
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let if_ = join_with_line(check_bindings, if_);
280
-
if if_false.is_empty() {
281
-
Ok(docvec![if_])
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+
let document = if if_false.is_empty() {
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+
if_
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} else {
283
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let else_ = docvec![" else ", break_block(if_false)];
284
-
Ok(docvec![if_, else_])
285
-
}
316
+
docvec![if_, else_]
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+
};
318
+
Ok(if has_assignments {
319
+
CaseBody::Statements(document)
320
+
} else {
321
+
CaseBody::If(document)
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+
})
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}
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}
288
325
+30
compiler-core/src/javascript/tests/case.rs
+30
compiler-core/src/javascript/tests/case.rs
···
413
413
"
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);
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}
416
+
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+
#[test]
418
+
fn list_with_guard() {
419
+
assert_js!(
420
+
"
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+
pub fn go(x) {
422
+
case x {
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+
[] -> 0
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+
[first, ..] if first < 10 -> first * 2
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+
[first, ..] -> first
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+
}
427
+
}
428
+
"
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+
);
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+
}
431
+
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+
#[test]
433
+
fn list_with_guard_no_binding() {
434
+
assert_js!(
435
+
"
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+
pub fn go(x) {
437
+
case x {
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+
[] -> 0
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+
[first, ..] if 1 < 10 -> first * 2
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+
[first, ..] -> first
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+
}
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+
}
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+
"
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+
);
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+
}
+6
-8
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__bit_arrays__case_bit_array_assignment_discard.snap
+6
-8
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__bit_arrays__case_bit_array_assignment_discard.snap
···
18
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if (x.bitSize === 8) {
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let n = x.byteAt(0);
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return n;
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-
} else {
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-
if (x.bitSize >= 8) {
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-
if ((x.bitSize - 8) % 8 === 0) {
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-
let n = x.byteAt(0);
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-
return n;
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-
} else {
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-
return 1;
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-
}
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+
} else if (x.bitSize >= 8) {
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+
if ((x.bitSize - 8) % 8 === 0) {
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+
let n = x.byteAt(0);
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+
return n;
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} else {
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return 1;
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}
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+
} else {
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+
return 1;
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}
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}
+13
-17
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__bit_arrays__case_bit_array_assignment_float.snap
+13
-17
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__bit_arrays__case_bit_array_assignment_float.snap
···
21
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if (bitArraySliceToFloat(x, 0, 64, true) === 3.14) {
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let pi = 3.14;
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return pi;
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-
} else {
25
-
if (bitArraySliceToFloat(x, 0, 64, true) === 1.1) {
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-
if ((x.bitSize - 64) % 8 === 0) {
27
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let pi = 1.1;
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-
return pi;
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-
} else {
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-
return 1.1;
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-
}
24
+
} else if (bitArraySliceToFloat(x, 0, 64, true) === 1.1) {
25
+
if ((x.bitSize - 64) % 8 === 0) {
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+
let pi = 1.1;
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+
return pi;
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28
} else {
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return 1.1;
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30
}
31
+
} else {
32
+
return 1.1;
35
33
}
36
-
} else {
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-
if (x.bitSize >= 64) {
38
-
if (bitArraySliceToFloat(x, 0, 64, true) === 1.1) {
39
-
if ((x.bitSize - 64) % 8 === 0) {
40
-
let pi = 1.1;
41
-
return pi;
42
-
} else {
43
-
return 1.1;
44
-
}
34
+
} else if (x.bitSize >= 64) {
35
+
if (bitArraySliceToFloat(x, 0, 64, true) === 1.1) {
36
+
if ((x.bitSize - 64) % 8 === 0) {
37
+
let pi = 1.1;
38
+
return pi;
45
39
} else {
46
40
return 1.1;
47
41
}
48
42
} else {
49
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return 1.1;
50
44
}
45
+
} else {
46
+
return 1.1;
51
47
}
52
48
}
+13
-17
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__bit_arrays__case_bit_array_assignment_int.snap
+13
-17
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__bit_arrays__case_bit_array_assignment_int.snap
···
19
19
if (x.byteAt(0) === 1) {
20
20
let n = 1;
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21
return n;
22
-
} else {
23
-
if (x.byteAt(0) === 2) {
24
-
if ((x.bitSize - 8) % 8 === 0) {
25
-
let n = 2;
26
-
return n;
27
-
} else {
28
-
return 1;
29
-
}
22
+
} else if (x.byteAt(0) === 2) {
23
+
if ((x.bitSize - 8) % 8 === 0) {
24
+
let n = 2;
25
+
return n;
30
26
} else {
31
27
return 1;
32
28
}
29
+
} else {
30
+
return 1;
33
31
}
34
-
} else {
35
-
if (x.bitSize >= 8) {
36
-
if (x.byteAt(0) === 2) {
37
-
if ((x.bitSize - 8) % 8 === 0) {
38
-
let n = 2;
39
-
return n;
40
-
} else {
41
-
return 1;
42
-
}
32
+
} else if (x.bitSize >= 8) {
33
+
if (x.byteAt(0) === 2) {
34
+
if ((x.bitSize - 8) % 8 === 0) {
35
+
let n = 2;
36
+
return n;
43
37
} else {
44
38
return 1;
45
39
}
46
40
} else {
47
41
return 1;
48
42
}
43
+
} else {
44
+
return 1;
49
45
}
50
46
}
+13
-17
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__bit_arrays__case_bit_array_assignment_string.snap
+13
-17
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__bit_arrays__case_bit_array_assignment_string.snap
···
23
23
x.byteAt(4) === 111) {
24
24
let message = "Hello";
25
25
return message;
26
-
} else {
27
-
if (x.byteAt(0) === 74 && x.byteAt(1) === 97 && x.byteAt(2) === 107) {
28
-
if ((x.bitSize - 24) % 8 === 0) {
29
-
let message = "Jak";
30
-
return message;
31
-
} else {
32
-
return "wibble";
33
-
}
26
+
} else if (x.byteAt(0) === 74 && x.byteAt(1) === 97 && x.byteAt(2) === 107) {
27
+
if ((x.bitSize - 24) % 8 === 0) {
28
+
let message = "Jak";
29
+
return message;
34
30
} else {
35
31
return "wibble";
36
32
}
33
+
} else {
34
+
return "wibble";
37
35
}
38
-
} else {
39
-
if (x.bitSize >= 24) {
40
-
if (x.byteAt(0) === 74 && x.byteAt(1) === 97 && x.byteAt(2) === 107) {
41
-
if ((x.bitSize - 24) % 8 === 0) {
42
-
let message = "Jak";
43
-
return message;
44
-
} else {
45
-
return "wibble";
46
-
}
36
+
} else if (x.bitSize >= 24) {
37
+
if (x.byteAt(0) === 74 && x.byteAt(1) === 97 && x.byteAt(2) === 107) {
38
+
if ((x.bitSize - 24) % 8 === 0) {
39
+
let message = "Jak";
40
+
return message;
47
41
} else {
48
42
return "wibble";
49
43
}
50
44
} else {
51
45
return "wibble";
52
46
}
47
+
} else {
48
+
return "wibble";
53
49
}
54
50
}
+31
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__case__list_with_guard.snap
+31
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__case__list_with_guard.snap
···
1
+
---
2
+
source: compiler-core/src/javascript/tests/case.rs
3
+
expression: "\npub fn go(x) {\n case x {\n [] -> 0\n [first, ..] if first < 10 -> first * 2\n [first, ..] -> first\n }\n}\n"
4
+
---
5
+
----- SOURCE CODE
6
+
7
+
pub fn go(x) {
8
+
case x {
9
+
[] -> 0
10
+
[first, ..] if first < 10 -> first * 2
11
+
[first, ..] -> first
12
+
}
13
+
}
14
+
15
+
16
+
----- COMPILED JAVASCRIPT
17
+
import { Empty as $Empty } from "../gleam.mjs";
18
+
19
+
export function go(x) {
20
+
if (x instanceof $Empty) {
21
+
return 0;
22
+
} else {
23
+
let first = x.head;
24
+
if (first < 10) {
25
+
return first * 2;
26
+
} else {
27
+
let first$1 = x.head;
28
+
return first$1;
29
+
}
30
+
}
31
+
}
+29
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__case__list_with_guard_no_binding.snap
+29
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__case__list_with_guard_no_binding.snap
···
1
+
---
2
+
source: compiler-core/src/javascript/tests/case.rs
3
+
expression: "\npub fn go(x) {\n case x {\n [] -> 0\n [first, ..] if 1 < 10 -> first * 2\n [first, ..] -> first\n }\n}\n"
4
+
---
5
+
----- SOURCE CODE
6
+
7
+
pub fn go(x) {
8
+
case x {
9
+
[] -> 0
10
+
[first, ..] if 1 < 10 -> first * 2
11
+
[first, ..] -> first
12
+
}
13
+
}
14
+
15
+
16
+
----- COMPILED JAVASCRIPT
17
+
import { Empty as $Empty } from "../gleam.mjs";
18
+
19
+
export function go(x) {
20
+
if (x instanceof $Empty) {
21
+
return 0;
22
+
} else if (1 < 10) {
23
+
let first = x.head;
24
+
return first * 2;
25
+
} else {
26
+
let first = x.head;
27
+
return first;
28
+
}
29
+
}
+3
-5
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__case__multi_subject_no_catch_all.snap
+3
-5
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__case__multi_subject_no_catch_all.snap
+3
-5
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__case__multi_subject_or.snap
+3
-5
compiler-core/src/javascript/tests/snapshots/gleam_core__javascript__tests__case__multi_subject_or.snap