Improve suggestion for extern crate self error message

src/test/ui/crate-loading/invalid-rlib.rs

@@ -6,3 +6,5 @@
 #![no_std]
 use ::foo; //~ ERROR invalid metadata files for crate `foo`
 //~| NOTE failed to mmap file
+//~^^ ERROR invalid metadata files for crate `foo`
+//~| NOTE failed to mmap file

src/test/ui/crate-loading/invalid-rlib.stderr

@@ -6,6 +6,14 @@ LL | use ::foo;
    |
    = note: failed to mmap file 'auxiliary/libfoo.rlib'
 
-error: aborting due to previous error
+error[E0786]: found invalid metadata files for crate `foo`
+  --> $DIR/invalid-rlib.rs:7:7
+   |
+LL | use ::foo;
+   |       ^^^
+   |
+   = note: failed to mmap file 'auxiliary/libfoo.rlib'
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0786`.

src/test/ui/extern-flag/empty-extern-arg.rs

@@ -1,4 +1,6 @@
 // compile-flags: --extern std=
 // error-pattern: extern location for std does not exist
+// needs-unwind since it affects the error output
+// ignore-emscripten compiled with panic=abort, personality not required
 
 fn main() {}

src/test/ui/extern/extern-crate-multiple-missing.rs

@@ -3,6 +3,8 @@ extern crate bar; //~ ERROR can't find crate for `bar`
 extern crate foo; //~ ERROR can't find crate for `foo`
 
 fn main() {
+    // If the crate name introduced by `extern crate` failed to resolve then subsequent
+    // derived paths do not emit additional errors
     foo::something();
     bar::something();
 }

src/test/ui/imports/extern-crate-self/extern-crate-self-fail.stderr

@@ -2,7 +2,12 @@ error: `extern crate self;` requires renaming
   --> $DIR/extern-crate-self-fail.rs:1:1
    |
 LL | extern crate self;
-   | ^^^^^^^^^^^^^^^^^^ help: try: `extern crate self as name;`
+   | ^^^^^^^^^^^^^^^^^^
+   |
+help: rename the `self` crate to be able to import it
+   |
+LL | extern crate self as name;
+   | ~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 error: `#[macro_use]` is not supported on `extern crate self`
   --> $DIR/extern-crate-self-fail.rs:3:1

src/test/ui/rust-2018/uniform-paths/deadlock.rs

@@ -1,7 +1,8 @@
 // edition:2018
 // compile-flags:--extern foo --extern bar
 
+use bar::foo; //~ ERROR can't find crate for `bar`
 use foo::bar; //~ ERROR can't find crate for `foo`
-use bar::foo;
+//~^^ ERROR unresolved imports `bar::foo`, `foo::bar`
 
 fn main() {}

src/test/ui/rust-2018/uniform-paths/deadlock.stderr

@@ -1,9 +1,24 @@
-error[E0463]: can't find crate for `foo`
+error[E0463]: can't find crate for `bar`
   --> $DIR/deadlock.rs:4:5
    |
+LL | use bar::foo;
+   |     ^^^ can't find crate
+
+error[E0463]: can't find crate for `foo`
+  --> $DIR/deadlock.rs:5:5
+   |
 LL | use foo::bar;
    |     ^^^ can't find crate
 
-error: aborting due to previous error
+error[E0432]: unresolved imports `bar::foo`, `foo::bar`
+  --> $DIR/deadlock.rs:4:5
+   |
+LL | use bar::foo;
+   |     ^^^^^^^^
+LL | use foo::bar;
+   |     ^^^^^^^^
 
-For more information about this error, try `rustc --explain E0463`.
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0432, E0463.
+For more information about an error, try `rustc --explain E0432`.