Give a better error message when linking to a macro with the wrong disambiguator

Before:

```
warning: unresolved link to `m`
 --> m.rs:1:6
  |
1 | /// [value@m]
  |      ^^^^^^^
  |
  = note: `#[warn(broken_intra_doc_links)]` on by default
  = note: no item named `m` is in scope
  = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
```

After:

```
warning: unresolved link to `m`
 --> m.rs:1:6
  |
1 | /// [value@m]
  |      ^^^^^^^ help: to link to the macro, use its disambiguator: `m!`
  |
  = note: `#[warn(broken_intra_doc_links)]` on by default
  = note: this link resolves to the macro `m`, which is not in the value namespace
```

2 files changed, 63 insertions, 10 deletions

diff --git a/src/test/rustdoc-ui/intra-link-errors.rs b/src/test/rustdoc-ui/intra-link-errors.rs
index ecf2b05e281..33c8d1b3c49 100644
--- a/src/test/rustdoc-ui/intra-link-errors.rs
+++ b/src/test/rustdoc-ui/intra-link-errors.rs
@@ -10,6 +10,18 @@
 //~| NOTE no item named `path::to` is in scope
 //~| HELP to escape
 
+/// [std::io::not::here]
+//~^ ERROR unresolved link
+//~| NOTE the module `io` has no inner item
+
+/// [std::io::Error::x]
+//~^ ERROR unresolved link
+//~| NOTE the struct `Error` has no field
+
+/// [std::io::ErrorKind::x]
+//~^ ERROR unresolved link
+//~| NOTE the enum `ErrorKind` has no variant
+
 /// [f::A]
 //~^ ERROR unresolved link
 //~| NOTE `f` is a function, not a module
@@ -60,3 +72,12 @@ impl S {
 pub trait T {
     fn g() {}
 }
+
+/// [m()]
+//~^ ERROR unresolved link
+//~| HELP to link to the macro
+//~| NOTE not in the value namespace
+#[macro_export]
+macro_rules! m {
+    () => {};
+}
diff --git a/src/test/rustdoc-ui/intra-link-errors.stderr b/src/test/rustdoc-ui/intra-link-errors.stderr
index ba091ff854c..0b9149cd8ea 100644
--- a/src/test/rustdoc-ui/intra-link-errors.stderr
+++ b/src/test/rustdoc-ui/intra-link-errors.stderr
@@ -12,16 +12,40 @@ LL | #![deny(broken_intra_doc_links)]
    = note: no item named `path::to` is in scope
    = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
 
-error: unresolved link to `f::A`
+error: unresolved link to `std::io::not::here`
   --> $DIR/intra-link-errors.rs:13:6
    |
+LL | /// [std::io::not::here]
+   |      ^^^^^^^^^^^^^^^^^^
+   |
+   = note: the module `io` has no inner item named `not`
+
+error: unresolved link to `std::io::Error::x`
+  --> $DIR/intra-link-errors.rs:17:6
+   |
+LL | /// [std::io::Error::x]
+   |      ^^^^^^^^^^^^^^^^^
+   |
+   = note: the struct `Error` has no field or associated item named `x`
+
+error: unresolved link to `std::io::ErrorKind::x`
+  --> $DIR/intra-link-errors.rs:21:6
+   |
+LL | /// [std::io::ErrorKind::x]
+   |      ^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: the enum `ErrorKind` has no variant or associated item named `x`
+
+error: unresolved link to `f::A`
+  --> $DIR/intra-link-errors.rs:25:6
+   |
 LL | /// [f::A]
    |      ^^^^
    |
    = note: `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:17:6
+  --> $DIR/intra-link-errors.rs:29:6
    |
 LL | /// [S::A]
    |      ^^^^
@@ -29,7 +53,7 @@ LL | /// [S::A]
    = note: the struct `S` has no field or associated item named `A`
 
 error: unresolved link to `S::fmt`
-  --> $DIR/intra-link-errors.rs:21:6
+  --> $DIR/intra-link-errors.rs:33:6
    |
 LL | /// [S::fmt]
    |      ^^^^^^
@@ -37,7 +61,7 @@ LL | /// [S::fmt]
    = note: the struct `S` has no field or associated item named `fmt`
 
 error: unresolved link to `E::D`
-  --> $DIR/intra-link-errors.rs:25:6
+  --> $DIR/intra-link-errors.rs:37:6
    |
 LL | /// [E::D]
    |      ^^^^
@@ -45,7 +69,7 @@ LL | /// [E::D]
    = note: the enum `E` has no variant or associated item named `D`
 
 error: unresolved link to `u8::not_found`
-  --> $DIR/intra-link-errors.rs:29:6
+  --> $DIR/intra-link-errors.rs:41:6
    |
 LL | /// [u8::not_found]
    |      ^^^^^^^^^^^^^
@@ -53,7 +77,7 @@ LL | /// [u8::not_found]
    = note: the builtin type `u8` does not have an associated item named `not_found`
 
 error: unresolved link to `S`
-  --> $DIR/intra-link-errors.rs:33:6
+  --> $DIR/intra-link-errors.rs:45:6
    |
 LL | /// [S!]
    |      ^^ help: to link to the struct, use its disambiguator: `struct@S`
@@ -61,7 +85,7 @@ LL | /// [S!]
    = note: this link resolves to the struct `S`, which is not in the macro namespace
 
 error: unresolved link to `T::g`
-  --> $DIR/intra-link-errors.rs:51:6
+  --> $DIR/intra-link-errors.rs:63:6
    |
 LL | /// [type@T::g]
    |      ^^^^^^^^^ help: to link to the associated function, use its disambiguator: `T::g()`
@@ -69,7 +93,7 @@ LL | /// [type@T::g]
    = note: this link resolves to the associated function `g`, which is not in the type namespace
 
 error: unresolved link to `T::h`
-  --> $DIR/intra-link-errors.rs:56:6
+  --> $DIR/intra-link-errors.rs:68:6
    |
 LL | /// [T::h!]
    |      ^^^^^
@@ -78,12 +102,20 @@ LL | /// [T::h!]
    = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
 
 error: unresolved link to `S::h`
-  --> $DIR/intra-link-errors.rs:43:6
+  --> $DIR/intra-link-errors.rs:55:6
    |
 LL | /// [type@S::h]
    |      ^^^^^^^^^ help: to link to the associated function, use its disambiguator: `S::h()`
    |
    = note: this link resolves to the associated function `h`, which is not in the type namespace
 
-error: aborting due to 10 previous errors
+error: unresolved link to `m`
+  --> $DIR/intra-link-errors.rs:76:6
+   |
+LL | /// [m()]
+   |      ^^^ help: to link to the macro, use its disambiguator: `m!`
+   |
+   = note: this link resolves to the macro `m`, which is not in the value namespace
+
+error: aborting due to 14 previous errors