diff options
Diffstat (limited to 'src/test/ui/functions-closures/closure-expected-type/supply-just-return-type.rs')
-rw-r--r-- | src/test/ui/functions-closures/closure-expected-type/supply-just-return-type.rs | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/src/test/ui/functions-closures/closure-expected-type/supply-just-return-type.rs b/src/test/ui/functions-closures/closure-expected-type/supply-just-return-type.rs new file mode 100644 index 000000000..e9964531c --- /dev/null +++ b/src/test/ui/functions-closures/closure-expected-type/supply-just-return-type.rs @@ -0,0 +1,26 @@ +// run-pass +fn with_closure<F, R>(f: F) -> Result<char, R> + where F: FnOnce(&char) -> Result<char, R>, +{ + f(&'a') +} + +fn main() { + // Test that supplying the `-> Result<char, ()>` manually here + // (which is needed to constrain `R`) still allows us to figure + // out that the type of `x` is `&'a char` where `'a` is bound in + // the closure (if we didn't, we'd get a type-error because + // `with_closure` requires a bound region). + // + // This pattern was found in the wild. + let z = with_closure(|x| -> Result<char, ()> { Ok(*x) }); + assert_eq!(z.unwrap(), 'a'); + + // It also works with `_`: + let z = with_closure(|x: _| -> Result<char, ()> { Ok(*x) }); + assert_eq!(z.unwrap(), 'a'); + + // It also works with `&_`: + let z = with_closure(|x: &_| -> Result<char, ()> { Ok(*x) }); + assert_eq!(z.unwrap(), 'a'); +} |