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Fix a bool payload beside a bool literal in an incomplete match - #9036
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Why:
`typeof x === "boolean" && x !== b` was simplified to the constant `!b`,
not to `x === !b` as its doc comment says. A match on a bool payload
beside a bool literal case produces this conjunction, so it never or
always took the payload arm (#9035).
JS modified (bool payload beside a bool literal):
Example:
@unboxed type t = | @as(true) LitTrue | AnyBool(bool) | AnyInt(int)
let f = (v: t) =>
switch v {
| AnyBool(_) => "bool"
| _ => "other"
}
Before (js):
function f(v) {
return "other";
}
After (js):
function f(v) {
if (v !== false) {
return "other";
} else {
return "bool";
}
}
Fixes #9035
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CMkrYaktctdKc4M41WF36t
Signed-off-by: Christoph Knittel <ck@cca.io>
Changelog🐛 Bug fix
Semantic Diff1 commit · Full page Simplify a boolean other than one to the other boolean717d266 · cknitt + Claude · Oct 25, 2026, 06:02 UTC
JS modified (bool payload beside a bool literal) @unboxed type t = | @as(true) LitTrue | AnyBool(bool) | AnyInt(int)
let f = (v: t) =>
switch v {
| AnyBool(_) => "bool"
| _ => "other"
}
function f(v) {
- return "other";
+ if (v !== false) {
+ return "other";
+ } else {
+ return "bool";
+ }
}Fixes #9035 |
|
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## master #9036 +/- ##
=======================================
Coverage 81.32% 81.33%
=======================================
Files 456 456
Lines 64042 64042
=======================================
+ Hits 52082 52086 +4
+ Misses 11960 11956 -4
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cristianoc
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Noticing the pr description is low quality.
While the commit description is medium quality.
We should look into improving the text of PR descriptions.
Fixes #9035.
Js_exp_make.simplify_and_rewrotetypeof x === "boolean" && x !== bto the constant!b. Its doc comment says the result isx === !b, which is the correct one. A match on a bool payload of an untagged variant, beside a bool literal case, produces exactly this conjunction. So in a match that doesn't name every case, the payload arm was never taken (@as(true)) or always taken (@as(false)).New test:
untagged_bool_payload_test.rescovers a bool payload beside@as(true)and beside@as(false), with values that aren't folded at compile time.Found by a review of the untagged variant work (#8950).
🤖 Generated with Claude Code
https://claude.ai/code/session_01CMkrYaktctdKc4M41WF36t