[WIP] give better errors for broken intra doc links

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

@@ -0,0 +1,59 @@
+#![deny(broken_intra_doc_links)]
+//~^ NOTE lint level is defined
+
+//! [std::io::oops]
+//! [std::io::oops::not::here]
+
+// FIXME: this should say that it was skipped (maybe an allowed by default lint?)
+/// [<invalid syntax>]
+
+// FIXME: this could say which path was the first to not be found (in this case, `path`)
+/// [path::to::nonexistent::module]
+//~^ ERROR unresolved link
+//~| NOTE no item named `path::to::nonexistent` is in scope
+//~| HELP to escape
+
+// TODO: why does this say `f` and not `f::A`??
+/// [f::A]
+//~^ ERROR unresolved link
+//~| NOTE no item named `f` is in scope
+//~| HELP to escape
+
+/// [S::A]
+//~^ ERROR unresolved link
+//~| NOTE this link partially resolves
+//~| NOTE `S` has no field
+
+/// [S::fmt]
+//~^ ERROR unresolved link
+//~| NOTE this link partially resolves
+//~| NOTE `S` has no field
+
+/// [E::D]
+//~^ ERROR unresolved link
+//~| NOTE this link partially resolves
+//~| NOTE `E` has no field
+
+/// [u8::not_found]
+//~^ ERROR unresolved link
+//~| NOTE the builtin type `u8` does not have an associated item named `not_found`
+
+/// [S!]
+//~^ ERROR unresolved link
+//~| HELP to link to the unit struct, use its disambiguator
+//~| NOTE this link resolves to the unit struct `S`
+pub fn f() {}
+#[derive(Debug)]
+pub struct S;
+
+pub enum E { A, B, C }
+
+/// [type@S::h]
+impl S {
+    pub fn h() {}
+}
+
+/// [type@T::g]
+pub trait T {
+    fn g() {}
+}