Rollup merge of #142805 - estebank:underscore-import, r=compiler-errors

Emit a single error when importing a path with `_`

When encountering `use _;`, `use _::*'` or similar, do not emit two errors for that single mistake. This also side-steps the issue of resolve errors suggesting adding a crate named `_` to `Cargo.toml`.

Fix rust-lang/rust#142662.

10 files changed, 188 insertions, 40 deletions

diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
index e989209e177..1b7a2c3bda0 100644
--- a/compiler/rustc_resolve/src/imports.rs
+++ b/compiler/rustc_resolve/src/imports.rs
@@ -608,7 +608,9 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             }
         }
 
-        self.throw_unresolved_import_error(errors, glob_error);
+        if !errors.is_empty() {
+            self.throw_unresolved_import_error(errors, glob_error);
+        }
     }
 
     pub(crate) fn check_hidden_glob_reexports(
@@ -688,14 +690,19 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             Some(def_id) if self.mods_with_parse_errors.contains(&def_id) => false,
             _ => true,
         });
+        errors.retain(|(_import, err)| {
+            // If we've encountered something like `use _;`, we've already emitted an error stating
+            // that `_` is not a valid identifier, so we ignore that resolve error.
+            err.segment != Some(kw::Underscore)
+        });
+
         if errors.is_empty() {
+            self.tcx.dcx().delayed_bug("expected a parse or \"`_` can't be an identifier\" error");
             return;
         }
 
-        /// Upper limit on the number of `span_label` messages.
-        const MAX_LABEL_COUNT: usize = 10;
-
         let span = MultiSpan::from_spans(errors.iter().map(|(_, err)| err.span).collect());
+
         let paths = errors
             .iter()
             .map(|(import, err)| {
@@ -715,6 +722,9 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             diag.note(note.clone());
         }
 
+        /// Upper limit on the number of `span_label` messages.
+        const MAX_LABEL_COUNT: usize = 10;
+
         for (import, err) in errors.into_iter().take(MAX_LABEL_COUNT) {
             if let Some(label) = err.label {
                 diag.span_label(err.span, label);
diff --git a/tests/ui/imports/multiple-extern-by-macro-for-underscore.stderr b/tests/ui/imports/multiple-extern-by-macro-for-underscore.ed2015.stderr
index 1da5aa87070..985cd654c39 100644
--- a/tests/ui/imports/multiple-extern-by-macro-for-underscore.stderr
+++ b/tests/ui/imports/multiple-extern-by-macro-for-underscore.ed2015.stderr
@@ -1,5 +1,5 @@
 error: expected identifier, found reserved identifier `_`
-  --> $DIR/multiple-extern-by-macro-for-underscore.rs:16:11
+  --> $DIR/multiple-extern-by-macro-for-underscore.rs:18:11
    |
 LL |     use ::_;
    |           ^ expected identifier, found reserved identifier
diff --git a/tests/ui/imports/multiple-extern-by-macro-for-underscore.ed2021.stderr b/tests/ui/imports/multiple-extern-by-macro-for-underscore.ed2021.stderr
new file mode 100644
index 00000000000..985cd654c39
--- /dev/null
+++ b/tests/ui/imports/multiple-extern-by-macro-for-underscore.ed2021.stderr
@@ -0,0 +1,8 @@
+error: expected identifier, found reserved identifier `_`
+  --> $DIR/multiple-extern-by-macro-for-underscore.rs:18:11
+   |
+LL |     use ::_;
+   |           ^ expected identifier, found reserved identifier
+
+error: aborting due to 1 previous error
+
diff --git a/tests/ui/imports/multiple-extern-by-macro-for-underscore.rs b/tests/ui/imports/multiple-extern-by-macro-for-underscore.rs
index ddf735d8947..ab877e06246 100644
--- a/tests/ui/imports/multiple-extern-by-macro-for-underscore.rs
+++ b/tests/ui/imports/multiple-extern-by-macro-for-underscore.rs
@@ -1,4 +1,6 @@
-//@ edition: 2021
+//@ revisions: ed2015 ed2021
+//@[ed2015] edition: 2015
+//@[ed2021] edition: 2021
 
 // issue#128813
 
diff --git a/tests/ui/underscore-imports/issue-110164.stderr b/tests/ui/underscore-imports/issue-110164.ed2015.stderr
index d8a4b6bbb75..f34b5ab5dde 100644
--- a/tests/ui/underscore-imports/issue-110164.stderr
+++ b/tests/ui/underscore-imports/issue-110164.ed2015.stderr
@@ -1,17 +1,17 @@
 error: expected identifier, found reserved identifier `_`
-  --> $DIR/issue-110164.rs:5:5
+  --> $DIR/issue-110164.rs:8:5
    |
 LL | use _::a;
    |     ^ expected identifier, found reserved identifier
 
 error: expected identifier, found reserved identifier `_`
-  --> $DIR/issue-110164.rs:8:5
+  --> $DIR/issue-110164.rs:10:5
    |
 LL | use _::*;
    |     ^ expected identifier, found reserved identifier
 
 error: expected identifier, found reserved identifier `_`
-  --> $DIR/issue-110164.rs:13:9
+  --> $DIR/issue-110164.rs:14:9
    |
 LL |     use _::a;
    |         ^ expected identifier, found reserved identifier
@@ -23,41 +23,17 @@ LL |     use _::*;
    |         ^ expected identifier, found reserved identifier
 
 error[E0432]: unresolved import `self::*`
-  --> $DIR/issue-110164.rs:1:5
+  --> $DIR/issue-110164.rs:4:5
    |
 LL | use self::*;
    |     ^^^^^^^ cannot glob-import a module into itself
 
 error[E0432]: unresolved import `crate::*`
-  --> $DIR/issue-110164.rs:3:5
+  --> $DIR/issue-110164.rs:6:5
    |
 LL | use crate::*;
    |     ^^^^^^^^ cannot glob-import a module into itself
 
-error[E0432]: unresolved import `_`
-  --> $DIR/issue-110164.rs:8:5
-   |
-LL | use _::*;
-   |     ^ `_` is not a valid crate or module name
-
-error[E0432]: unresolved import `_`
-  --> $DIR/issue-110164.rs:5:5
-   |
-LL | use _::a;
-   |     ^ `_` is not a valid crate or module name
-
-error[E0432]: unresolved import `_`
-  --> $DIR/issue-110164.rs:13:9
-   |
-LL |     use _::a;
-   |         ^ `_` is not a valid crate or module name
-
-error[E0432]: unresolved import `_`
-  --> $DIR/issue-110164.rs:16:9
-   |
-LL |     use _::*;
-   |         ^ `_` is not a valid crate or module name
-
-error: aborting due to 10 previous errors
+error: aborting due to 6 previous errors
 
 For more information about this error, try `rustc --explain E0432`.
diff --git a/tests/ui/underscore-imports/issue-110164.ed2021.stderr b/tests/ui/underscore-imports/issue-110164.ed2021.stderr
new file mode 100644
index 00000000000..f34b5ab5dde
--- /dev/null
+++ b/tests/ui/underscore-imports/issue-110164.ed2021.stderr
@@ -0,0 +1,39 @@
+error: expected identifier, found reserved identifier `_`
+  --> $DIR/issue-110164.rs:8:5
+   |
+LL | use _::a;
+   |     ^ expected identifier, found reserved identifier
+
+error: expected identifier, found reserved identifier `_`
+  --> $DIR/issue-110164.rs:10:5
+   |
+LL | use _::*;
+   |     ^ expected identifier, found reserved identifier
+
+error: expected identifier, found reserved identifier `_`
+  --> $DIR/issue-110164.rs:14:9
+   |
+LL |     use _::a;
+   |         ^ expected identifier, found reserved identifier
+
+error: expected identifier, found reserved identifier `_`
+  --> $DIR/issue-110164.rs:16:9
+   |
+LL |     use _::*;
+   |         ^ expected identifier, found reserved identifier
+
+error[E0432]: unresolved import `self::*`
+  --> $DIR/issue-110164.rs:4:5
+   |
+LL | use self::*;
+   |     ^^^^^^^ cannot glob-import a module into itself
+
+error[E0432]: unresolved import `crate::*`
+  --> $DIR/issue-110164.rs:6:5
+   |
+LL | use crate::*;
+   |     ^^^^^^^^ cannot glob-import a module into itself
+
+error: aborting due to 6 previous errors
+
+For more information about this error, try `rustc --explain E0432`.
diff --git a/tests/ui/underscore-imports/issue-110164.rs b/tests/ui/underscore-imports/issue-110164.rs
index 6fd13414500..bb080c5e471 100644
--- a/tests/ui/underscore-imports/issue-110164.rs
+++ b/tests/ui/underscore-imports/issue-110164.rs
@@ -1,19 +1,18 @@
+//@ revisions: ed2015 ed2021
+//@[ed2015] edition: 2015
+//@[ed2021] edition: 2021
 use self::*;
 //~^ ERROR unresolved import `self::*`
 use crate::*;
 //~^ ERROR unresolved import `crate::*`
 use _::a;
 //~^ ERROR expected identifier, found reserved identifier `_`
-//~| ERROR unresolved import `_`
 use _::*;
 //~^ ERROR expected identifier, found reserved identifier `_`
-//~| ERROR unresolved import `_`
 
 fn main() {
     use _::a;
     //~^ ERROR expected identifier, found reserved identifier `_`
-    //~| ERROR unresolved import `_`
     use _::*;
     //~^ ERROR expected identifier, found reserved identifier `_`
-    //~| ERROR unresolved import `_`
 }
diff --git a/tests/ui/underscore-imports/multiple-uses.ed2015.stderr b/tests/ui/underscore-imports/multiple-uses.ed2015.stderr
new file mode 100644
index 00000000000..a295586fa16
--- /dev/null
+++ b/tests/ui/underscore-imports/multiple-uses.ed2015.stderr
@@ -0,0 +1,49 @@
+error: expected identifier, found reserved identifier `_`
+  --> $DIR/multiple-uses.rs:4:9
+   |
+LL | pub use _::{a, b};
+   |         ^ expected identifier, found reserved identifier
+
+error: expected identifier, found reserved identifier `_`
+  --> $DIR/multiple-uses.rs:6:18
+   |
+LL | pub use std::{a, _};
+   |                  ^ expected identifier, found reserved identifier
+
+error: expected identifier, found reserved identifier `_`
+  --> $DIR/multiple-uses.rs:9:18
+   |
+LL | pub use std::{b, _, c};
+   |                  ^ expected identifier, found reserved identifier
+
+error: expected identifier, found reserved identifier `_`
+  --> $DIR/multiple-uses.rs:12:15
+   |
+LL | pub use std::{_, d};
+   |               ^ expected identifier, found reserved identifier
+
+error[E0432]: unresolved import `std::a`
+  --> $DIR/multiple-uses.rs:6:15
+   |
+LL | pub use std::{a, _};
+   |               ^ no `a` in the root
+
+error[E0432]: unresolved imports `std::b`, `std::c`
+  --> $DIR/multiple-uses.rs:9:15
+   |
+LL | pub use std::{b, _, c};
+   |               ^     ^
+   |               |     |
+   |               |     no `c` in the root
+   |               |     help: a similar name exists in the module: `rc`
+   |               no `b` in the root
+
+error[E0432]: unresolved import `std::d`
+  --> $DIR/multiple-uses.rs:12:18
+   |
+LL | pub use std::{_, d};
+   |                  ^ no `d` in the root
+
+error: aborting due to 7 previous errors
+
+For more information about this error, try `rustc --explain E0432`.
diff --git a/tests/ui/underscore-imports/multiple-uses.ed2021.stderr b/tests/ui/underscore-imports/multiple-uses.ed2021.stderr
new file mode 100644
index 00000000000..a295586fa16
--- /dev/null
+++ b/tests/ui/underscore-imports/multiple-uses.ed2021.stderr
@@ -0,0 +1,49 @@
+error: expected identifier, found reserved identifier `_`
+  --> $DIR/multiple-uses.rs:4:9
+   |
+LL | pub use _::{a, b};
+   |         ^ expected identifier, found reserved identifier
+
+error: expected identifier, found reserved identifier `_`
+  --> $DIR/multiple-uses.rs:6:18
+   |
+LL | pub use std::{a, _};
+   |                  ^ expected identifier, found reserved identifier
+
+error: expected identifier, found reserved identifier `_`
+  --> $DIR/multiple-uses.rs:9:18
+   |
+LL | pub use std::{b, _, c};
+   |                  ^ expected identifier, found reserved identifier
+
+error: expected identifier, found reserved identifier `_`
+  --> $DIR/multiple-uses.rs:12:15
+   |
+LL | pub use std::{_, d};
+   |               ^ expected identifier, found reserved identifier
+
+error[E0432]: unresolved import `std::a`
+  --> $DIR/multiple-uses.rs:6:15
+   |
+LL | pub use std::{a, _};
+   |               ^ no `a` in the root
+
+error[E0432]: unresolved imports `std::b`, `std::c`
+  --> $DIR/multiple-uses.rs:9:15
+   |
+LL | pub use std::{b, _, c};
+   |               ^     ^
+   |               |     |
+   |               |     no `c` in the root
+   |               |     help: a similar name exists in the module: `rc`
+   |               no `b` in the root
+
+error[E0432]: unresolved import `std::d`
+  --> $DIR/multiple-uses.rs:12:18
+   |
+LL | pub use std::{_, d};
+   |                  ^ no `d` in the root
+
+error: aborting due to 7 previous errors
+
+For more information about this error, try `rustc --explain E0432`.
diff --git a/tests/ui/underscore-imports/multiple-uses.rs b/tests/ui/underscore-imports/multiple-uses.rs
new file mode 100644
index 00000000000..31dd1862429
--- /dev/null
+++ b/tests/ui/underscore-imports/multiple-uses.rs
@@ -0,0 +1,16 @@
+//@ revisions: ed2015 ed2021
+//@[ed2015] edition: 2015
+//@[ed2021] edition: 2021
+pub use _::{a, b};
+//~^ ERROR expected identifier, found reserved identifier `_`
+pub use std::{a, _};
+//~^ ERROR expected identifier, found reserved identifier `_`
+//~| ERROR unresolved import `std::a`
+pub use std::{b, _, c};
+//~^ ERROR expected identifier, found reserved identifier `_`
+//~| ERROR unresolved imports `std::b`, `std::c`
+pub use std::{_, d};
+//~^ ERROR expected identifier, found reserved identifier `_`
+//~| ERROR unresolved import `std::d`
+
+fn main() {}