Add regression test for rust-lang#105404

Author: GuillaumeGomez

src/test/rustdoc-ui/unable-fulfill-trait.rs

@@ -0,0 +1,13 @@
+// This test ensures that it's not crashing rustdoc.
+
+pub struct Foo<'a, 'b, T> {
+    field1: dyn Bar<'a, 'b,>,
+    //~^ ERROR
+    //~^^ ERROR
+}
+
+pub trait Bar<'x, 's, U>
+    where U: 'x,
+    Self:'x,
+    Self:'s
+{}

src/test/rustdoc-ui/unable-fulfill-trait.stderr

@@ -0,0 +1,26 @@
+error[E0107]: this trait takes 1 generic argument but 0 generic arguments were supplied
+  --> $DIR/unable-fulfill-trait.rs:4:17
+   |
+LL |     field1: dyn Bar<'a, 'b,>,
+   |                 ^^^ expected 1 generic argument
+   |
+note: trait defined here, with 1 generic parameter: `U`
+  --> $DIR/unable-fulfill-trait.rs:9:11
+   |
+LL | pub trait Bar<'x, 's, U>
+   |           ^^^         -
+help: add missing generic argument
+   |
+LL |     field1: dyn Bar<'a, 'b, U,>,
+   |                           +++
+
+error[E0227]: ambiguous lifetime bound, explicit lifetime bound required
+  --> $DIR/unable-fulfill-trait.rs:4:13
+   |
+LL |     field1: dyn Bar<'a, 'b,>,
+   |             ^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0107, E0227.
+For more information about an error, try `rustc --explain E0107`.