Add a couple more tests + address review comments

src/librustc_resolve/resolve_imports.rs

@@ -192,6 +192,7 @@ impl<'a, 'crateloader> Resolver<'a, 'crateloader> {
                                       ident.name == keywords::SelfValue.name() {
                                 // FIXME: Implement these with renaming requirements so that e.g.
                                 // `use super;` doesn't work, but `use super as name;` does.
+                                // Fall through here to get an error from `early_resolve_...`.
                             }
                         }
 
@@ -940,7 +941,12 @@ impl<'a, 'b:'a, 'c: 'b> ImportResolver<'a, 'b, 'c> {
                     }
                 }
                 Err(..) => {
-                    assert!(result[ns].get().is_err());
+                    // FIXME: This assert may fire if public glob is later shadowed by a private
+                    // single import (see test `issue-55884-2.rs`). In theory single imports should
+                    // always block globs, even if they are not yet resolved, so that this kind of
+                    // self-inconsistent resolution never happens.
+                    // Reenable the assert when the issue is fixed.
+                    // assert!(result[ns].get().is_err());
                 }
             }
         });

src/test/ui/imports/auxiliary/glob-conflict.rs

@@ -0,0 +1,9 @@
+mod m1 {
+    pub fn f() {}
+}
+mod m2 {
+    pub fn f(_: u8) {}
+}
+
+pub use m1::*;
+pub use m2::*;

src/test/ui/imports/glob-conflict-cross-crate.rs

@@ -0,0 +1,7 @@
+// aux-build:glob-conflict.rs
+
+extern crate glob_conflict;
+
+fn main() {
+    glob_conflict::f(); //~ ERROR cannot find function `f` in module `glob_conflict`
+}

src/test/ui/imports/glob-conflict-cross-crate.stderr

@@ -0,0 +1,9 @@
+error[E0425]: cannot find function `f` in module `glob_conflict`
+  --> $DIR/glob-conflict-cross-crate.rs:6:20
+   |
+LL |     glob_conflict::f(); //~ ERROR cannot find function `f` in module `glob_conflict`
+   |                    ^ not found in `glob_conflict`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0425`.

src/test/ui/imports/issue-55884-1.rs

@@ -0,0 +1,21 @@
+mod m {
+    mod m1 {
+        pub struct S {}
+    }
+    mod m2 {
+        // Note this derive, it makes this struct macro-expanded,
+        // so it doesn't appear in time to participate in the initial resolution of `use m::S`,
+        // only in the later validation pass.
+        #[derive(Default)]
+        pub struct S {}
+    }
+
+    // Create a glob vs glob ambiguity
+    pub use self::m1::*;
+    pub use self::m2::*;
+}
+
+fn main() {
+    use m::S; //~ ERROR `S` is ambiguous
+    let s = S {};
+}

src/test/ui/imports/issue-55884-1.stderr

@@ -0,0 +1,22 @@
+error[E0659]: `S` is ambiguous (glob import vs glob import in the same module)
+  --> $DIR/issue-55884-1.rs:19:12
+   |
+LL |     use m::S; //~ ERROR `S` is ambiguous
+   |            ^ ambiguous name
+   |
+note: `S` could refer to the struct imported here
+  --> $DIR/issue-55884-1.rs:14:13
+   |
+LL |     pub use self::m1::*;
+   |             ^^^^^^^^^^^
+   = help: consider adding an explicit import of `S` to disambiguate
+note: `S` could also refer to the struct imported here
+  --> $DIR/issue-55884-1.rs:15:13
+   |
+LL |     pub use self::m2::*;
+   |             ^^^^^^^^^^^
+   = help: consider adding an explicit import of `S` to disambiguate
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0659`.

src/test/ui/imports/issue-55884-2.rs

@@ -0,0 +1,14 @@
+mod options {
+    pub struct ParseOptions {}
+}
+
+mod parser {
+    pub use options::*;
+    // Private single import shadows public glob import, but arrives too late for initial
+    // resolution of `use parser::ParseOptions` because it depends on that resolution itself.
+    use ParseOptions;
+}
+
+pub use parser::ParseOptions; //~ ERROR struct `ParseOptions` is private
+
+fn main() {}

src/test/ui/imports/issue-55884-2.stderr

@@ -0,0 +1,9 @@
+error[E0603]: struct `ParseOptions` is private
+  --> $DIR/issue-55884-2.rs:12:17
+   |
+LL | pub use parser::ParseOptions; //~ ERROR struct `ParseOptions` is private
+   |                 ^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0603`.

src/test/ui/rust-2018/local-path-suggestions-2018.rs

@@ -19,7 +19,7 @@ mod foo {
 }
 
 mod bazz {
-    use foo::Bar;
+    use foo::Bar; //~ ERROR unresolved import `foo`
 
     fn baz() {
         let x: Bar = 22;
@@ -28,6 +28,6 @@ mod bazz {
 
 use foo::Bar;
 
-use foobar::Baz;
+use foobar::Baz; //~ ERROR unresolved import `foobar`
 
 fn main() { }

src/test/ui/rust-2018/local-path-suggestions-2018.stderr

@@ -1,15 +1,15 @@
 error[E0432]: unresolved import `foo`
   --> $DIR/local-path-suggestions-2018.rs:22:9
    |
-LL |     use foo::Bar;
+LL |     use foo::Bar; //~ ERROR unresolved import `foo`
    |         ^^^ did you mean `crate::foo`?
    |
    = note: `use` statements changed in Rust 2018; read more at <https://doc.rust-lang.org/edition-guide/rust-2018/module-system/path-clarity.html>
 
 error[E0432]: unresolved import `foobar`
   --> $DIR/local-path-suggestions-2018.rs:31:5
    |
-LL | use foobar::Baz;
+LL | use foobar::Baz; //~ ERROR unresolved import `foobar`
    |     ^^^^^^ did you mean `baz::foobar`?
 
 error: aborting due to 2 previous errors

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

@@ -0,0 +1,7 @@
+// edition:2018
+// compile-flags:--extern foo --extern bar
+
+use foo::bar; //~ ERROR unresolved import
+use bar::foo;
+
+fn main() {}

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

@@ -0,0 +1,9 @@
+error[E0432]: unresolved import
+  --> $DIR/deadlock.rs:4:5
+   |
+LL | use foo::bar; //~ ERROR unresolved import
+   |     ^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0432`.

src/test/ui/rust-2018/uniform-paths/issue-54390.rs

@@ -0,0 +1,11 @@
+// edition:2018
+
+#![deny(unused)]
+
+use std::fmt;
+
+// No "unresolved import" + "unused import" combination here.
+use fmt::Write; //~ ERROR imports can only refer to extern crate names
+                //~| ERROR unused import: `fmt::Write`
+
+fn main() {}

src/test/ui/rust-2018/uniform-paths/issue-54390.stderr

@@ -0,0 +1,32 @@
+error[E0658]: imports can only refer to extern crate names passed with `--extern` on stable channel (see issue #53130)
+  --> $DIR/issue-54390.rs:8:5
+   |
+LL | use std::fmt;
+   |     -------- not an extern crate passed with `--extern`
+...
+LL | use fmt::Write; //~ ERROR imports can only refer to extern crate names
+   |     ^^^
+   |
+   = help: add #![feature(uniform_paths)] to the crate attributes to enable
+note: this import refers to the module imported here
+  --> $DIR/issue-54390.rs:5:5
+   |
+LL | use std::fmt;
+   |     ^^^^^^^^
+
+error: unused import: `fmt::Write`
+  --> $DIR/issue-54390.rs:8:5
+   |
+LL | use fmt::Write; //~ ERROR imports can only refer to extern crate names
+   |     ^^^^^^^^^^
+   |
+note: lint level defined here
+  --> $DIR/issue-54390.rs:3:9
+   |
+LL | #![deny(unused)]
+   |         ^^^^^^
+   = note: #[deny(unused_imports)] implied by #[deny(unused)]
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0658`.