gleam 1.18.1
The pattern match below should take the 400 branch, but in gleam javascript it takes the 999 branch.
Also note this bug is not caused exclusively by guards (see second repro), it's about string matches "shadowing" prefix matches when they shouldn't.
pub fn w1(s: String, x: Int) -> Int {
case s, x {
"ab", y if y > 4 -> 1
"a" <> _, _ -> 400
_, _ -> 999
}
}
pub fn main() {
echo w1("ab", 1)
}Compiles to:
export function w1(s, x) {
if (s === "ab") {
let y = x;
if (y > 4) {
return 1;
} else {
return 999;
}
} else if (s.charCodeAt(0) === 97) {
return 400;
} else {
return 999;
}
}Second one: should be 502 but prints 999
import gleam/string
pub type Shape {
Circle(r: Int)
Square(s: Int)
Rect(w: Int, h: Int)
}
pub type Wrap {
Wrapped(v: Shape)
Empty
}
pub fn a(w: Wrap, s: String) -> Int {
case w, s {
_, "ab" -> 100
Wrapped(Square(0)), "ab" <> _ -> 200
Wrapped(_), "a" <> r -> 500 + string.length(r)
_, _ -> 999
}
}
pub fn main() {
echo a(Wrapped(Rect(2, 1)), "abc")
}
gleam 1.18.1
The pattern match below should take the
400branch, but in gleam javascript it takes the999branch.Also note this bug is not caused exclusively by guards (see second repro), it's about string matches "shadowing" prefix matches when they shouldn't.
Compiles to:
Second one: should be 502 but prints 999