Try to suggest dereferences when trait selection failed.

src/test/ui/traits/trait-suggest-deferences-issue-39029.fixed

@@ -0,0 +1,18 @@
+// run-rustfix
+use std::net::TcpListener;
+
+struct NoToSocketAddrs(String);
+
+impl std::ops::Deref for NoToSocketAddrs {
+    type Target = String;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+fn main() {
+    let _works = TcpListener::bind("some string");
+    let bad = NoToSocketAddrs("bad".to_owned());
+    let _errors = TcpListener::bind(&*bad);
+    //~^ ERROR the trait bound `NoToSocketAddrs: std::net::ToSocketAddrs` is not satisfied
+}

src/test/ui/traits/trait-suggest-deferences-issue-39029.rs

@@ -0,0 +1,18 @@
+// run-rustfix
+use std::net::TcpListener;
+
+struct NoToSocketAddrs(String);
+
+impl std::ops::Deref for NoToSocketAddrs {
+    type Target = String;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+fn main() {
+    let _works = TcpListener::bind("some string");
+    let bad = NoToSocketAddrs("bad".to_owned());
+    let _errors = TcpListener::bind(&bad);
+    //~^ ERROR the trait bound `NoToSocketAddrs: std::net::ToSocketAddrs` is not satisfied
+}

src/test/ui/traits/trait-suggest-deferences-issue-39029.stderr

@@ -0,0 +1,19 @@
+error[E0277]: the trait bound `NoToSocketAddrs: std::net::ToSocketAddrs` is not satisfied
+  --> $DIR/trait-suggest-deferences-issue-39029.rs:16:37
+   |
+LL |     let _errors = TcpListener::bind(&bad);
+   |                                     ^^^^
+   |                                     |
+   |                                     the trait `std::net::ToSocketAddrs` is not implemented for `NoToSocketAddrs`
+   |                                     help: consider adding dereference here: `&*bad`
+   | 
+  ::: $SRC_DIR/libstd/net/tcp.rs:LL:COL
+   |
+LL |     pub fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<TcpListener> {
+   |                    ------------- required by this bound in `std::net::TcpListener::bind`
+   |
+   = note: required because of the requirements on the impl of `std::net::ToSocketAddrs` for `&NoToSocketAddrs`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.

src/test/ui/traits/trait-suggest-deferences-issue-62530.fixed

@@ -0,0 +1,15 @@
+// run-rustfix
+fn takes_str(_x: &str) {}
+
+fn takes_type_parameter<T>(_x: T) where T: SomeTrait {}
+
+trait SomeTrait {}
+impl SomeTrait for &'_ str {}
+impl SomeTrait for char {}
+
+fn main() {
+    let string = String::new();
+    takes_str(&string);             // Ok
+    takes_type_parameter(&*string);  // Error
+    //~^ ERROR the trait bound `&std::string::String: SomeTrait` is not satisfied
+}

src/test/ui/traits/trait-suggest-deferences-issue-62530.rs

@@ -0,0 +1,15 @@
+// run-rustfix
+fn takes_str(_x: &str) {}
+
+fn takes_type_parameter<T>(_x: T) where T: SomeTrait {}
+
+trait SomeTrait {}
+impl SomeTrait for &'_ str {}
+impl SomeTrait for char {}
+
+fn main() {
+    let string = String::new();
+    takes_str(&string);             // Ok
+    takes_type_parameter(&string);  // Error
+    //~^ ERROR the trait bound `&std::string::String: SomeTrait` is not satisfied
+}

src/test/ui/traits/trait-suggest-deferences-issue-62530.stderr

@@ -0,0 +1,15 @@
+error[E0277]: the trait bound `&std::string::String: SomeTrait` is not satisfied
+  --> $DIR/trait-suggest-deferences-issue-62530.rs:13:26
+   |
+LL | fn takes_type_parameter<T>(_x: T) where T: SomeTrait {}
+   |                                            --------- required by this bound in `takes_type_parameter`
+...
+LL |     takes_type_parameter(&string);  // Error
+   |                          ^^^^^^^
+   |                          |
+   |                          the trait `SomeTrait` is not implemented for `&std::string::String`
+   |                          help: consider adding dereference here: `&*string`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.

src/test/ui/traits/trait-suggest-deferences-multiple.fixed

@@ -0,0 +1,36 @@
+// run-rustfix
+use std::ops::Deref;
+
+trait Happy {}
+struct LDM;
+impl Happy for &LDM {}
+
+struct Foo(LDM);
+struct Bar(Foo);
+struct Baz(Bar);
+impl Deref for Foo {
+    type Target = LDM;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+impl Deref for Bar {
+    type Target = Foo;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+impl Deref for Baz {
+    type Target = Bar;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+fn foo<T>(_: T) where T: Happy {}
+
+fn main() {
+    let baz = Baz(Bar(Foo(LDM)));
+    foo(&***baz);
+    //~^ ERROR the trait bound `&Baz: Happy` is not satisfied
+}

src/test/ui/traits/trait-suggest-deferences-multiple.rs

@@ -0,0 +1,36 @@
+// run-rustfix
+use std::ops::Deref;
+
+trait Happy {}
+struct LDM;
+impl Happy for &LDM {}
+
+struct Foo(LDM);
+struct Bar(Foo);
+struct Baz(Bar);
+impl Deref for Foo {
+    type Target = LDM;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+impl Deref for Bar {
+    type Target = Foo;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+impl Deref for Baz {
+    type Target = Bar;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+fn foo<T>(_: T) where T: Happy {}
+
+fn main() {
+    let baz = Baz(Bar(Foo(LDM)));
+    foo(&baz);
+    //~^ ERROR the trait bound `&Baz: Happy` is not satisfied
+}

src/test/ui/traits/trait-suggest-deferences-multiple.stderr

@@ -0,0 +1,15 @@
+error[E0277]: the trait bound `&Baz: Happy` is not satisfied
+  --> $DIR/trait-suggest-deferences-multiple.rs:34:9
+   |
+LL | fn foo<T>(_: T) where T: Happy {}
+   |                          ----- required by this bound in `foo`
+...
+LL |     foo(&baz);
+   |         ^^^^
+   |         |
+   |         the trait `Happy` is not implemented for `&Baz`
+   |         help: consider adding dereference here: `&***baz`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.