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Do recursive shrinking without recursive function calls #294

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Do recursive shrinking without recursive function calls #294

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473b6a0
impl: do recursive shrinking without recursive fn call
neithernut Jun 12, 2021
d930487
impl: move shrinking logic out of inline function
neithernut Jun 12, 2021
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38 changes: 15 additions & 23 deletions src/tester.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -364,12 +364,14 @@ impl<T: Testable,
$($name: Arbitrary + Debug),*> Testable for fn($($name),*) -> T {
#[allow(non_snake_case)]
fn result(&self, g: &mut Gen) -> TestResult {
fn shrink_failure<T: Testable, $($name: Arbitrary + Debug),*>(
g: &mut Gen,
self_: fn($($name),*) -> T,
a: ($($name,)*),
) -> Option<TestResult> {
for t in a.shrink() {
let self_ = *self;
let a: ($($name,)*) = Arbitrary::arbitrary(g);
let ( $($name,)* ) = a.clone();
let mut r = safe(move || {self_($($name),*)}).result(g);

if r.is_failure() {
let mut a = a.shrink();
while let Some(t) = a.next() {
let ($($name,)*) = t.clone();
let mut r_new = safe(move || {self_($($name),*)}).result(g);
if r_new.is_failure() {
Expand All @@ -378,28 +380,18 @@ impl<T: Testable,
r_new.arguments = Some(debug_reprs(&[$($name),*]));
}

// The shrunk value *does* witness a failure, so keep
// trying to shrink it.
let shrunk = shrink_failure(g, self_, t);
// The shrunk value *does* witness a failure, so remember
// it for now
r = r_new;

// If we couldn't witness a failure on any shrunk value,
// then return the failure we already have.
return Some(shrunk.unwrap_or(r_new))
// ... and switch over to that value, i.e. try to shrink
// it further.
a = t.shrink()
}
}
None
}

let self_ = *self;
let a: ($($name,)*) = Arbitrary::arbitrary(g);
let ( $($name,)* ) = a.clone();
let r = safe(move || {self_($($name),*)}).result(g);
match r.status {
Pass|Discard => r,
Fail => {
shrink_failure(g, self_, a).unwrap_or(r)
}
}
r
}
}}}

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