Use multiline note for trait suggestion

src/librustc_typeck/check/method/suggest.rs

@@ -228,7 +228,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                     macro_rules! report_function {
                         ($span:expr, $name:expr) => {
                             err.note(&format!("{} is a function, perhaps you wish to call it",
-                                         $name));
+                                              $name));
                         }
                     }
 
@@ -315,9 +315,9 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             let mut candidates = valid_out_of_scope_traits;
             candidates.sort();
             candidates.dedup();
-            let msg = format!("items from traits can only be used if the trait is in scope; the \
-                               following {traits_are} implemented but not in scope, perhaps add \
-                               a `use` for {one_of_them}:",
+            let mut msg = format!("items from traits can only be used if the trait is in scope; \
+                                   the following {traits_are} implemented but not in scope, \
+                                   perhaps add a `use` for {one_of_them}:",
                               traits_are = if candidates.len() == 1 {
                                   "trait is"
                               } else {
@@ -329,17 +329,17 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                                   "one of them"
                               });
 
-            err.help(&msg[..]);
-
             let limit = if candidates.len() == 5 { 5 } else { 4 };
             for (i, trait_did) in candidates.iter().take(limit).enumerate() {
-                err.help(&format!("candidate #{}: `use {};`",
-                                  i + 1,
-                                  self.tcx.item_path_str(*trait_did)));
+                msg.push_str(&format!("\ncandidate #{}: `use {};`",
+                                      i + 1,
+                                      self.tcx.item_path_str(*trait_did)));
             }
             if candidates.len() > limit {
-                err.note(&format!("and {} others", candidates.len() - limit));
+                msg.push_str(&format!("\nand {} others", candidates.len() - limit));
             }
+            err.help(&msg[..]);
+
             return;
         }
 
@@ -369,28 +369,27 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             // FIXME #21673 this help message could be tuned to the case
             // of a type parameter: suggest adding a trait bound rather
             // than implementing.
-            let msg = format!("items from traits can only be used if the trait is implemented \
-                               and in scope; the following {traits_define} an item `{name}`, \
-                               perhaps you need to implement {one_of_them}:",
-                              traits_define = if candidates.len() == 1 {
-                                  "trait defines"
-                              } else {
-                                  "traits define"
-                              },
-                              one_of_them = if candidates.len() == 1 {
-                                  "it"
-                              } else {
-                                  "one of them"
-                              },
-                              name = item_name);
-
-            err.help(&msg[..]);
+            let mut msg = format!("items from traits can only be used if the trait is implemented \
+                                   and in scope; the following {traits_define} an item `{name}`, \
+                                   perhaps you need to implement {one_of_them}:",
+                                  traits_define = if candidates.len() == 1 {
+                                      "trait defines"
+                                  } else {
+                                      "traits define"
+                                  },
+                                  one_of_them = if candidates.len() == 1 {
+                                      "it"
+                                  } else {
+                                      "one of them"
+                                  },
+                                  name = item_name);
 
             for (i, trait_info) in candidates.iter().enumerate() {
-                err.help(&format!("candidate #{}: `{}`",
-                                  i + 1,
-                                  self.tcx.item_path_str(trait_info.def_id)));
+                msg.push_str(&format!("\ncandidate #{}: `{}`",
+                                      i + 1,
+                                      self.tcx.item_path_str(trait_info.def_id)));
             }
+            err.help(&msg[..]);
         }
     }
 

src/test/ui/impl-trait/issue-21659-show-relevant-trait-impls-3.stderr

@@ -0,0 +1,11 @@
+error[E0599]: no method named `foo` found for type `Bar` in the current scope
+  --> $DIR/issue-21659-show-relevant-trait-impls-3.rs:30:8
+   |
+30 |     f1.foo(1usize);
+   |        ^^^
+   |
+   = help: items from traits can only be used if the trait is implemented and in scope; the following trait defines an item `foo`, perhaps you need to implement it:
+           candidate #1: `Foo`
+
+error: aborting due to previous error(s)
+

src/test/ui/impl-trait/method-suggestion-no-duplication.stderr

@@ -0,0 +1,13 @@
+error[E0599]: no method named `is_empty` found for type `Foo` in the current scope
+  --> $DIR/method-suggestion-no-duplication.rs:19:15
+   |
+19 |     foo(|s| s.is_empty());
+   |               ^^^^^^^^
+   |
+   = help: items from traits can only be used if the trait is implemented and in scope; the following traits define an item `is_empty`, perhaps you need to implement one of them:
+           candidate #1: `std::iter::ExactSizeIterator`
+           candidate #2: `core::slice::SliceExt`
+           candidate #3: `core::str::StrExt`
+
+error: aborting due to previous error(s)
+

src/test/ui/impl-trait/no-method-suggested-traits.rs

@@ -0,0 +1,133 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// aux-build:no_method_suggested_traits.rs
+extern crate no_method_suggested_traits;
+
+struct Foo;
+enum Bar { X }
+
+mod foo {
+    pub trait Bar {
+        fn method(&self) {}
+
+        fn method2(&self) {}
+    }
+
+    impl Bar for u32 {}
+
+    impl Bar for char {}
+}
+
+fn main() {
+    // test the values themselves, and autoderef.
+
+
+    1u32.method();
+    //~^ HELP following traits are implemented but not in scope, perhaps add a `use` for one of them
+    //~| ERROR no method named
+    //~| HELP `use foo::Bar;`
+    //~| HELP `use no_method_suggested_traits::foo::PubPub;`
+    std::rc::Rc::new(&mut Box::new(&1u32)).method();
+    //~^ HELP following traits are implemented but not in scope, perhaps add a `use` for one of them
+    //~| ERROR no method named
+    //~| HELP `use foo::Bar;`
+    //~| HELP `use no_method_suggested_traits::foo::PubPub;`
+
+    'a'.method();
+    //~^ ERROR no method named
+    //~| HELP the following trait is implemented but not in scope, perhaps add a `use` for it:
+    //~| HELP `use foo::Bar;`
+    std::rc::Rc::new(&mut Box::new(&'a')).method();
+    //~^ ERROR no method named
+    //~| HELP the following trait is implemented but not in scope, perhaps add a `use` for it:
+    //~| HELP `use foo::Bar;`
+
+    1i32.method();
+    //~^ ERROR no method named
+    //~| HELP the following trait is implemented but not in scope, perhaps add a `use` for it:
+    //~| HELP `use no_method_suggested_traits::foo::PubPub;`
+    std::rc::Rc::new(&mut Box::new(&1i32)).method();
+    //~^ ERROR no method named
+    //~| HELP the following trait is implemented but not in scope, perhaps add a `use` for it:
+    //~| HELP `use no_method_suggested_traits::foo::PubPub;`
+
+    Foo.method();
+    //~^ ERROR no method named
+    //~| HELP following traits define an item `method`, perhaps you need to implement one of them
+    //~| HELP `foo::Bar`
+    //~| HELP `no_method_suggested_traits::foo::PubPub`
+    //~| HELP `no_method_suggested_traits::Reexported`
+    //~| HELP `no_method_suggested_traits::bar::PubPriv`
+    //~| HELP `no_method_suggested_traits::qux::PrivPub`
+    //~| HELP `no_method_suggested_traits::quz::PrivPriv`
+    std::rc::Rc::new(&mut Box::new(&Foo)).method();
+    //~^ ERROR no method named
+    //~| HELP following traits define an item `method`, perhaps you need to implement one of them
+    //~| HELP `foo::Bar`
+    //~| HELP `no_method_suggested_traits::foo::PubPub`
+    //~| HELP `no_method_suggested_traits::Reexported`
+    //~| HELP `no_method_suggested_traits::bar::PubPriv`
+    //~| HELP `no_method_suggested_traits::qux::PrivPub`
+    //~| HELP `no_method_suggested_traits::quz::PrivPriv`
+
+    1u64.method2();
+    //~^ ERROR no method named
+    //~| HELP the following trait defines an item `method2`, perhaps you need to implement it
+    //~| HELP `foo::Bar`
+    std::rc::Rc::new(&mut Box::new(&1u64)).method2();
+    //~^ ERROR no method named
+    //~| HELP the following trait defines an item `method2`, perhaps you need to implement it
+    //~| HELP `foo::Bar`
+
+    no_method_suggested_traits::Foo.method2();
+    //~^ ERROR no method named
+    //~| HELP following trait defines an item `method2`, perhaps you need to implement it
+    //~| HELP `foo::Bar`
+    std::rc::Rc::new(&mut Box::new(&no_method_suggested_traits::Foo)).method2();
+    //~^ ERROR no method named
+    //~| HELP following trait defines an item `method2`, perhaps you need to implement it
+    //~| HELP `foo::Bar`
+    no_method_suggested_traits::Bar::X.method2();
+    //~^ ERROR no method named
+    //~| HELP following trait defines an item `method2`, perhaps you need to implement it
+    //~| HELP `foo::Bar`
+    std::rc::Rc::new(&mut Box::new(&no_method_suggested_traits::Bar::X)).method2();
+    //~^ ERROR no method named
+    //~| HELP following trait defines an item `method2`, perhaps you need to implement it
+    //~| HELP `foo::Bar`
+
+    Foo.method3();
+    //~^ ERROR no method named
+    //~| HELP following trait defines an item `method3`, perhaps you need to implement it
+    //~| HELP `no_method_suggested_traits::foo::PubPub`
+    std::rc::Rc::new(&mut Box::new(&Foo)).method3();
+    //~^ ERROR no method named
+    //~| HELP following trait defines an item `method3`, perhaps you need to implement it
+    //~| HELP `no_method_suggested_traits::foo::PubPub`
+    Bar::X.method3();
+    //~^ ERROR no method named
+    //~| HELP following trait defines an item `method3`, perhaps you need to implement it
+    //~| HELP `no_method_suggested_traits::foo::PubPub`
+    std::rc::Rc::new(&mut Box::new(&Bar::X)).method3();
+    //~^ ERROR no method named
+    //~| HELP following trait defines an item `method3`, perhaps you need to implement it
+    //~| HELP `no_method_suggested_traits::foo::PubPub`
+
+    // should have no help:
+    1_usize.method3(); //~ ERROR no method named
+    std::rc::Rc::new(&mut Box::new(&1_usize)).method3(); //~ ERROR no method named
+    no_method_suggested_traits::Foo.method3();  //~ ERROR no method named
+    std::rc::Rc::new(&mut Box::new(&no_method_suggested_traits::Foo)).method3();
+    //~^ ERROR no method named
+    no_method_suggested_traits::Bar::X.method3();  //~ ERROR no method named
+    std::rc::Rc::new(&mut Box::new(&no_method_suggested_traits::Bar::X)).method3();
+    //~^ ERROR no method named
+}