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langref: mention error union switch peer resolution

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dweiller 2023-12-08 20:16:11 +11:00
parent 6a18cee3af
commit 8695bc7ed3
1 changed files with 26 additions and 0 deletions
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26
doc/langref.html.in
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@ -6801,6 +6801,32 @@ test "peer type resolution: *const T and ?*T" {
try expect(a == b);
try expect(b == a);
}
test "peer type resolution: error union switch" {
// The non-error and error cases are only peers if the error case is just a switch expression;
// the pattern `if (x) {...} else |err| blk: { switch (err) {...} }` does not consider the
// non-error and error case to be peers.
var a: error{ A, B, C }!u32 = 0;
_ = &a;
const b = if (a) |x|
x + 3
else |err| switch (err) {
error.A => 0,
error.B => 1,
error.C => null,
};
try expect(@TypeOf(b) == ?u32);
// The non-error and error cases are only peers if the error case is just a switch expression;
// the pattern `x catch |err| blk: { switch (err) {...} }` does not consider the unwrapped `x`
// and error case to be peers.
const c = a catch |err| switch (err) {
error.A => 0,
error.B => 1,
error.C => null,
};
try expect(@TypeOf(c) == ?u32);
}
{#code_end#}
{#header_close#}
{#header_close#}