Suggest the right help message for as_ref

2 files changed, 55 insertions, 0 deletions

diff --git a/src/test/ui/issues/issue-100605.rs b/src/test/ui/issues/issue-100605.rs
new file mode 100644
index 00000000000..917a45c15bb
--- /dev/null
+++ b/src/test/ui/issues/issue-100605.rs
@@ -0,0 +1,9 @@
+fn takes_option(_arg: Option<&String>) {}
+
+fn main() {
+    takes_option(&None); //~ ERROR 4:18: 4:23: mismatched types [E0308]
+
+    let x = String::from("x");
+    let res = Some(x);
+    takes_option(&res); //~ ERROR 8:18: 8:22: mismatched types [E0308]
+}
diff --git a/src/test/ui/issues/issue-100605.stderr b/src/test/ui/issues/issue-100605.stderr
new file mode 100644
index 00000000000..886e3cd6bb7
--- /dev/null
+++ b/src/test/ui/issues/issue-100605.stderr
@@ -0,0 +1,46 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-100605.rs:4:18
+   |
+LL |     takes_option(&None);
+   |     ------------ ^^^^^ expected enum `Option`, found `&Option<_>`
+   |     |
+   |     arguments to this function are incorrect
+   |
+   = note:   expected enum `Option<&String>`
+           found reference `&Option<_>`
+note: function defined here
+  --> $DIR/issue-100605.rs:1:4
+   |
+LL | fn takes_option(_arg: Option<&String>) {}
+   |    ^^^^^^^^^^^^ ---------------------
+help: you can convert from `&Option<T>` to `Option<&T>` using `.as_ref()`
+   |
+LL |     takes_option(None.as_ref());
+   |                  ~~~~~~~~~~~~~
+help: consider removing the borrow
+   |
+LL -     takes_option(&None);
+LL +     takes_option(None);
+   |
+
+error[E0308]: mismatched types
+  --> $DIR/issue-100605.rs:8:18
+   |
+LL |     takes_option(&res);
+   |     ------------ ^^^^
+   |     |            |
+   |     |            expected enum `Option`, found `&Option<String>`
+   |     |            help: you can convert from `&Option<T>` to `Option<&T>` using `.as_ref()`: `res.as_ref()`
+   |     arguments to this function are incorrect
+   |
+   = note:   expected enum `Option<&String>`
+           found reference `&Option<String>`
+note: function defined here
+  --> $DIR/issue-100605.rs:1:4
+   |
+LL | fn takes_option(_arg: Option<&String>) {}
+   |    ^^^^^^^^^^^^ ---------------------
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.