Improve rustdoc error for failed intra-doc link resolution

The previous error was confusing since it made it sound like you can't
link to items that are defined outside the current module.

Also suggested importing the item.

Author: camelid

src/librustdoc/passes/collect_intra_doc_links.rs

@@ -1575,17 +1575,17 @@ fn resolution_failure(
                         _ => None,
                     };
                     // See if this was a module: `[path]` or `[std::io::nope]`
-                    if let Some(module) = last_found_module {
-                        let module_name = collector.cx.tcx.item_name(module);
+                    if let Some(_module) = last_found_module {
                         let note = format!(
-                            "the module `{}` contains no item named `{}`",
-                            module_name, unresolved
+                            "there is no item named `{}` in scope",
+                            unresolved
                         );
                         if let Some(span) = sp {
                             diag.span_label(span, &note);
                         } else {
                             diag.note(&note);
                         }
+                        diag.help(&format!("did you mean to import `{}`?", unresolved));
                         // If the link has `::` in it, assume it was meant to be an intra-doc link.
                         // Otherwise, the `[]` might be unrelated.
                         // FIXME: don't show this for autolinks (`<>`), `()` style links, or reference links

src/test/rustdoc-ui/deny-intra-link-resolution-failure.stderr

@@ -2,13 +2,14 @@ error: unresolved link to `v2`
   --> $DIR/deny-intra-link-resolution-failure.rs:3:6
    |
 LL | /// [v2]
-   |      ^^ the module `deny_intra_link_resolution_failure` contains no item named `v2`
+   |      ^^ there is no item named `v2` in scope
    |
 note: the lint level is defined here
   --> $DIR/deny-intra-link-resolution-failure.rs:1:9
    |
 LL | #![deny(broken_intra_doc_links)]
    |         ^^^^^^^^^^^^^^^^^^^^^^
+   = help: did you mean to import `v2`?
    = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
 
 error: aborting due to previous error

src/test/rustdoc-ui/intra-link-errors.rs

@@ -6,23 +6,28 @@
 
 /// [path::to::nonexistent::module]
 //~^ ERROR unresolved link
-//~| NOTE `intra_link_errors` contains no item named `path`
+//~| NOTE there is no item named `path` in scope
+//~| HELP did you mean to import `path`?
 
 /// [path::to::nonexistent::macro!]
 //~^ ERROR unresolved link
-//~| NOTE `intra_link_errors` contains no item named `path`
+//~| NOTE there is no item named `path` in scope
+//~| HELP did you mean to import `path`?
 
 /// [type@path::to::nonexistent::type]
 //~^ ERROR unresolved link
-//~| NOTE `intra_link_errors` contains no item named `path`
+//~| NOTE there is no item named `path` in scope
+//~| HELP did you mean to import `path`?
 
 /// [std::io::not::here]
 //~^ ERROR unresolved link
-//~| NOTE `io` contains no item named `not`
+//~| NOTE there is no item named `not` in scope
+//~| HELP did you mean to import `not`?
 
 /// [type@std::io::not::here]
 //~^ ERROR unresolved link
-//~| NOTE `io` contains no item named `not`
+//~| NOTE there is no item named `not` in scope
+//~| HELP did you mean to import `not`?
 
 /// [std::io::Error::x]
 //~^ ERROR unresolved link

src/test/rustdoc-ui/intra-link-errors.stderr

@@ -2,94 +2,103 @@ error: unresolved link to `path::to::nonexistent::module`
   --> $DIR/intra-link-errors.rs:7:6
    |
 LL | /// [path::to::nonexistent::module]
-   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the module `intra_link_errors` contains no item named `path`
+   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ there is no item named `path` in scope
    |
 note: the lint level is defined here
   --> $DIR/intra-link-errors.rs:1:9
    |
 LL | #![deny(broken_intra_doc_links)]
    |         ^^^^^^^^^^^^^^^^^^^^^^
+   = help: did you mean to import `path`?
 
 error: unresolved link to `path::to::nonexistent::macro`
-  --> $DIR/intra-link-errors.rs:11:6
+  --> $DIR/intra-link-errors.rs:12:6
    |
 LL | /// [path::to::nonexistent::macro!]
-   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the module `intra_link_errors` contains no item named `path`
+   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ there is no item named `path` in scope
+   |
+   = help: did you mean to import `path`?
 
 error: unresolved link to `path::to::nonexistent::type`
-  --> $DIR/intra-link-errors.rs:15:6
+  --> $DIR/intra-link-errors.rs:17:6
    |
 LL | /// [type@path::to::nonexistent::type]
-   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the module `intra_link_errors` contains no item named `path`
+   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ there is no item named `path` in scope
+   |
+   = help: did you mean to import `path`?
 
 error: unresolved link to `std::io::not::here`
-  --> $DIR/intra-link-errors.rs:19:6
+  --> $DIR/intra-link-errors.rs:22:6
    |
 LL | /// [std::io::not::here]
-   |      ^^^^^^^^^^^^^^^^^^ the module `io` contains no item named `not`
+   |      ^^^^^^^^^^^^^^^^^^ there is no item named `not` in scope
+   |
+   = help: did you mean to import `not`?
 
 error: unresolved link to `std::io::not::here`
-  --> $DIR/intra-link-errors.rs:23:6
+  --> $DIR/intra-link-errors.rs:27:6
    |
 LL | /// [type@std::io::not::here]
-   |      ^^^^^^^^^^^^^^^^^^^^^^^ the module `io` contains no item named `not`
+   |      ^^^^^^^^^^^^^^^^^^^^^^^ there is no item named `not` in scope
+   |
+   = help: did you mean to import `not`?
 
 error: unresolved link to `std::io::Error::x`
-  --> $DIR/intra-link-errors.rs:27:6
+  --> $DIR/intra-link-errors.rs:32:6
    |
 LL | /// [std::io::Error::x]
    |      ^^^^^^^^^^^^^^^^^ the struct `Error` has no field or associated item named `x`
 
 error: unresolved link to `std::io::ErrorKind::x`
-  --> $DIR/intra-link-errors.rs:31:6
+  --> $DIR/intra-link-errors.rs:36:6
    |
 LL | /// [std::io::ErrorKind::x]
    |      ^^^^^^^^^^^^^^^^^^^^^ the enum `ErrorKind` has no variant or associated item named `x`
 
 error: unresolved link to `f::A`
-  --> $DIR/intra-link-errors.rs:35:6
+  --> $DIR/intra-link-errors.rs:40:6
    |
 LL | /// [f::A]
    |      ^^^^ `f` is a function, not a module or type, and cannot have associated items
 
 error: unresolved link to `f::A`
-  --> $DIR/intra-link-errors.rs:39:6
+  --> $DIR/intra-link-errors.rs:44:6
    |
 LL | /// [f::A!]
    |      ^^^^^ `f` is a function, not a module or type, and cannot have associated items
 
 error: unresolved link to `S::A`
-  --> $DIR/intra-link-errors.rs:43:6
+  --> $DIR/intra-link-errors.rs:48:6
    |
 LL | /// [S::A]
    |      ^^^^ the struct `S` has no field or associated item named `A`
 
 error: unresolved link to `S::fmt`
-  --> $DIR/intra-link-errors.rs:47:6
+  --> $DIR/intra-link-errors.rs:52:6
    |
 LL | /// [S::fmt]
    |      ^^^^^^ the struct `S` has no field or associated item named `fmt`
 
 error: unresolved link to `E::D`
-  --> $DIR/intra-link-errors.rs:51:6
+  --> $DIR/intra-link-errors.rs:56:6
    |
 LL | /// [E::D]
    |      ^^^^ the enum `E` has no variant or associated item named `D`
 
 error: unresolved link to `u8::not_found`
-  --> $DIR/intra-link-errors.rs:55:6
+  --> $DIR/intra-link-errors.rs:60:6
    |
 LL | /// [u8::not_found]
    |      ^^^^^^^^^^^^^ the builtin type `u8` has no associated item named `not_found`
 
 error: unresolved link to `std::primitive::u8::not_found`
-  --> $DIR/intra-link-errors.rs:59:6
+  --> $DIR/intra-link-errors.rs:64:6
    |
 LL | /// [std::primitive::u8::not_found]
    |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the builtin type `u8` has no associated item named `not_found`
 
 error: unresolved link to `Vec::into_iter`
-  --> $DIR/intra-link-errors.rs:63:6
+  --> $DIR/intra-link-errors.rs:68:6
    |
 LL | /// [type@Vec::into_iter]
    |      ^^^^^^^^^^^^^^^^^^^
@@ -98,7 +107,7 @@ LL | /// [type@Vec::into_iter]
    |      help: to link to the associated function, add parentheses: `Vec::into_iter()`
 
 error: unresolved link to `S`
-  --> $DIR/intra-link-errors.rs:68:6
+  --> $DIR/intra-link-errors.rs:73:6
    |
 LL | /// [S!]
    |      ^^
@@ -107,7 +116,7 @@ LL | /// [S!]
    |      help: to link to the struct, prefix with `struct@`: `struct@S`
 
 error: unresolved link to `T::g`
-  --> $DIR/intra-link-errors.rs:86:6
+  --> $DIR/intra-link-errors.rs:91:6
    |
 LL | /// [type@T::g]
    |      ^^^^^^^^^
@@ -116,13 +125,13 @@ LL | /// [type@T::g]
    |      help: to link to the associated function, add parentheses: `T::g()`
 
 error: unresolved link to `T::h`
-  --> $DIR/intra-link-errors.rs:91:6
+  --> $DIR/intra-link-errors.rs:96:6
    |
 LL | /// [T::h!]
    |      ^^^^^ the trait `T` has no macro named `h`
 
 error: unresolved link to `S::h`
-  --> $DIR/intra-link-errors.rs:78:6
+  --> $DIR/intra-link-errors.rs:83:6
    |
 LL | /// [type@S::h]
    |      ^^^^^^^^^
@@ -131,7 +140,7 @@ LL | /// [type@S::h]
    |      help: to link to the associated function, add parentheses: `S::h()`
 
 error: unresolved link to `m`
-  --> $DIR/intra-link-errors.rs:98:6
+  --> $DIR/intra-link-errors.rs:103:6
    |
 LL | /// [m()]
    |      ^^^

src/test/rustdoc-ui/intra-link-span-ice-55723.stderr

@@ -2,13 +2,14 @@ error: unresolved link to `i`
   --> $DIR/intra-link-span-ice-55723.rs:9:10
    |
 LL | /// （arr[i]）
-   |           ^ the module `intra_link_span_ice_55723` contains no item named `i`
+   |           ^ there is no item named `i` in scope
    |
 note: the lint level is defined here
   --> $DIR/intra-link-span-ice-55723.rs:1:9
    |
 LL | #![deny(broken_intra_doc_links)]
    |         ^^^^^^^^^^^^^^^^^^^^^^
+   = help: did you mean to import `i`?
    = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
 
 error: aborting due to previous error

src/test/rustdoc-ui/intra-links-warning-crlf.stderr

@@ -2,33 +2,37 @@ warning: unresolved link to `error`
   --> $DIR/intra-links-warning-crlf.rs:7:6
    |
 LL | /// [error]
-   |      ^^^^^ the module `intra_links_warning_crlf` contains no item named `error`
+   |      ^^^^^ there is no item named `error` in scope
    |
    = note: `#[warn(broken_intra_doc_links)]` on by default
+   = help: did you mean to import `error`?
    = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
 
 warning: unresolved link to `error1`
   --> $DIR/intra-links-warning-crlf.rs:12:11
    |
 LL | /// docs [error1]
-   |           ^^^^^^ the module `intra_links_warning_crlf` contains no item named `error1`
+   |           ^^^^^^ there is no item named `error1` in scope
    |
+   = help: did you mean to import `error1`?
    = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
 
 warning: unresolved link to `error2`
   --> $DIR/intra-links-warning-crlf.rs:15:11
    |
 LL | /// docs [error2]
-   |           ^^^^^^ the module `intra_links_warning_crlf` contains no item named `error2`
+   |           ^^^^^^ there is no item named `error2` in scope
    |
+   = help: did you mean to import `error2`?
    = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
 
 warning: unresolved link to `error`
   --> $DIR/intra-links-warning-crlf.rs:23:20
    |
 LL |  * It also has an [error].
-   |                    ^^^^^ the module `intra_links_warning_crlf` contains no item named `error`
+   |                    ^^^^^ there is no item named `error` in scope
    |
+   = help: did you mean to import `error`?
    = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
 
 warning: 4 warnings emitted