RFC 1940 housekeeping

[zackmdavis]

• move test to own directory, as requested in Tracking issue for RFC 1940: allow #[must_use] on functions #43302 (comment)
• exercise trait methods in test
• unstable book section

r? @nikomatsakis

[zackmdavis]

@nikomatsakis (Or am I reading your comment too literally?—if the tests were already just one file, maybe that counts as "collected".)

[zackmdavis]

The test diff makes more sense with looser-than-default rename detection (--find-renames=40%):

diff --git a/src/test/ui/lint/fn_must_use.rs b/src/test/ui/rfc_1940-must_use_on_functions/fn_must_use.rs
similarity index 47%
rename from src/test/ui/lint/fn_must_use.rs
rename to src/test/ui/rfc_1940-must_use_on_functions/fn_must_use.rs
index c549ded..7eb4c329 100644
--- a/src/test/ui/lint/fn_must_use.rs+++ b/src/test/ui/rfc_1940-must_use_on_functions/fn_must_use.rs@@ -12,7 +12,7 @@
#![warn(unused_must_use)]
struct MyStruct {
- n: usize+ n: usize,
}
impl MyStruct {
@@ -22,7 +22,34 @@ impl MyStruct {
}
}
-#[must_use="it's important"]+trait EvenNature {+ #[must_use = "no side effects"]+ fn is_even(&self) -> bool;+}++impl EvenNature for MyStruct {+ fn is_even(&self) -> bool {+ self.n % 2 == 0+ }+}++trait Replaceable {+ fn replace(&mut self, substitute: usize) -> usize;+}++impl Replaceable for MyStruct {+ // ↓ N.b.: `#[must_use]` attribute on a particular trait implementation+ // method won't work; the attribute should be on the method signature in+ // the trait's definition.+ #[must_use]+ fn replace(&mut self, substitute: usize) -> usize {+ let previously = self.n;+ self.n = substitute;+ previously+ }+}++#[must_use = "it's important"]
fn need_to_use_this_value() -> bool {
false
}
@@ -30,6 +57,14 @@ fn need_to_use_this_value() -> bool {
fn main() {
need_to_use_this_value();
- let m = MyStruct { n: 2 };+ let mut m = MyStruct { n: 2 };
m.need_to_use_this_method_value();
+ m.is_even(); // trait method!++ m.replace(3);++ 2.eq(&3);++ // FIXME: operators should probably be `must_use` if underlying method is+ 2 == 3;
}
diff --git a/src/test/ui/lint/fn_must_use.stderr b/src/test/ui/rfc_1940-must_use_on_functions/fn_must_use.stderr
similarity index 45%
rename from src/test/ui/lint/fn_must_use.stderr
rename to src/test/ui/rfc_1940-must_use_on_functions/fn_must_use.stderr
index 2428377..69755c8 100644
--- a/src/test/ui/lint/fn_must_use.stderr+++ b/src/test/ui/rfc_1940-must_use_on_functions/fn_must_use.stderr@@ -1,7 +1,7 @@
warning: unused return value of `need_to_use_this_value` which must be used: it's important
- --> $DIR/fn_must_use.rs:31:5+ --> $DIR/fn_must_use.rs:58:5
|
-31 | need_to_use_this_value();+58 | need_to_use_this_value();
| ^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: lint level defined here
@@ -11,8 +11,20 @@ note: lint level defined here
| ^^^^^^^^^^^^^^^
warning: unused return value of `MyStruct::need_to_use_this_method_value` which must be used
- --> $DIR/fn_must_use.rs:34:5+ --> $DIR/fn_must_use.rs:61:5
|
-34 | m.need_to_use_this_method_value();+61 | m.need_to_use_this_method_value();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+warning: unused return value of `EvenNature::is_even` which must be used: no side effects+ --> $DIR/fn_must_use.rs:62:5+ |+62 | m.is_even(); // trait method!+ | ^^^^^^^^^^^^++warning: unused return value of `std::cmp::PartialEq::eq` which must be used+ --> $DIR/fn_must_use.rs:66:5+ |+66 | 2.eq(&3);+ | ^^^^^^^^^+

[nikomatsakis]

@bors r+

@zackmdavis this looks nice to me; I'm not that picky, but I do want to be able to easily get an overview of the current behavior, and this PR seems to enable that.

[bors]

📌 Commit d09db63 has been approved by nikomatsakis

[bors]

⌛ Testing commit d09db63 with merge 325ba23...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing 325ba23 to master...