Omit unnecessary help to add #[cfg(test)] when already annotated

compiler/rustc_resolve/src/check_unused.rs

@@ -315,21 +315,28 @@ impl Resolver<'_> {
                 "remove the unused import"
             };
 
-            let parent_module = visitor.r.get_nearest_non_block_module(
-                visitor.r.local_def_id(unused.use_tree_id).to_def_id(),
-            );
-            let test_module_span = match module_to_string(parent_module) {
-                Some(module)
-                    if module == "test"
-                        || module == "tests"
-                        || module.starts_with("test_")
-                        || module.starts_with("tests_")
-                        || module.ends_with("_test")
-                        || module.ends_with("_tests") =>
-                {
-                    Some(parent_module.span)
+            // If we are in the `--test` mode, suppress a help that adds the `#[cfg(test)]`
+            // attribute; however, if not, suggest adding the attribute. There is no way to
+            // retrieve attributes here because we do not have a `TyCtxt` yet.
+            let test_module_span = if visitor.r.session.opts.test {
+                None
+            } else {
+                let parent_module = visitor.r.get_nearest_non_block_module(
+                    visitor.r.local_def_id(unused.use_tree_id).to_def_id(),
+                );
+                match module_to_string(parent_module) {
+                    Some(module)
+                        if module == "test"
+                            || module == "tests"
+                            || module.starts_with("test_")
+                            || module.starts_with("tests_")
+                            || module.ends_with("_test")
+                            || module.ends_with("_tests") =>
+                    {
+                        Some(parent_module.span)
+                    }
+                    _ => None,
                 }
-                _ => None,
             };
 
             visitor.r.lint_buffer.buffer_lint_with_diagnostic(

src/test/ui/imports/unused-imports-in-test-mode.rs

@@ -0,0 +1,84 @@
+// compile-flags: --test
+
+#![deny(unused_imports)]
+
+use std::io::BufRead; //~ ERROR unused import: `std::io::BufRead`
+
+fn a() {}
+fn b() {}
+
+mod test {
+    use super::a;  //~ ERROR unused import: `super::a`
+
+    fn foo() {
+        use crate::b;  //~ ERROR unused import: `crate::b`
+    }
+}
+
+mod tests {
+    use super::a;  //~ ERROR unused import: `super::a`
+
+    fn foo() {
+        use crate::b;  //~ ERROR unused import: `crate::b`
+    }
+}
+
+mod test_a {
+    use super::a;  //~ ERROR unused import: `super::a`
+
+    fn foo() {
+        use crate::b;  //~ ERROR unused import: `crate::b`
+    }
+}
+
+mod a_test {
+    use super::a;  //~ ERROR unused import: `super::a`
+
+    fn foo() {
+        use crate::b;  //~ ERROR unused import: `crate::b`
+    }
+}
+
+mod tests_a {
+    use super::a;  //~ ERROR unused import: `super::a`
+
+    fn foo() {
+        use crate::b;  //~ ERROR unused import: `crate::b`
+    }
+}
+
+mod a_tests {
+    use super::a;  //~ ERROR unused import: `super::a`
+
+    fn foo() {
+        use crate::b;  //~ ERROR unused import: `crate::b`
+    }
+}
+
+mod fastest_search {
+    use super::a;  //~ ERROR unused import: `super::a`
+
+    fn foo() {
+        use crate::b;  //~ ERROR unused import: `crate::b`
+    }
+}
+
+#[cfg(test)]
+mod test_has_attr {
+    use super::a;  //~ ERROR unused import: `super::a`
+
+    fn foo() {
+        use crate::b;  //~ ERROR unused import: `crate::b`
+    }
+}
+
+mod test_has_no_attr {
+    #[cfg(test)]
+    use super::a;  //~ ERROR unused import: `super::a`
+
+    fn foo() {
+        use crate::b;  //~ ERROR unused import: `crate::b`
+    }
+}
+
+fn main() {}

src/test/ui/imports/unused-imports-in-test-mode.stderr

@@ -0,0 +1,122 @@
+error: unused import: `std::io::BufRead`
+  --> $DIR/unused-imports-in-test-mode.rs:5:5
+   |
+LL | use std::io::BufRead;
+   |     ^^^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/unused-imports-in-test-mode.rs:3:9
+   |
+LL | #![deny(unused_imports)]
+   |         ^^^^^^^^^^^^^^
+
+error: unused import: `super::a`
+  --> $DIR/unused-imports-in-test-mode.rs:11:9
+   |
+LL |     use super::a;
+   |         ^^^^^^^^
+
+error: unused import: `crate::b`
+  --> $DIR/unused-imports-in-test-mode.rs:14:13
+   |
+LL |         use crate::b;
+   |             ^^^^^^^^
+
+error: unused import: `super::a`
+  --> $DIR/unused-imports-in-test-mode.rs:19:9
+   |
+LL |     use super::a;
+   |         ^^^^^^^^
+
+error: unused import: `crate::b`
+  --> $DIR/unused-imports-in-test-mode.rs:22:13
+   |
+LL |         use crate::b;
+   |             ^^^^^^^^
+
+error: unused import: `super::a`
+  --> $DIR/unused-imports-in-test-mode.rs:27:9
+   |
+LL |     use super::a;
+   |         ^^^^^^^^
+
+error: unused import: `crate::b`
+  --> $DIR/unused-imports-in-test-mode.rs:30:13
+   |
+LL |         use crate::b;
+   |             ^^^^^^^^
+
+error: unused import: `super::a`
+  --> $DIR/unused-imports-in-test-mode.rs:35:9
+   |
+LL |     use super::a;
+   |         ^^^^^^^^
+
+error: unused import: `crate::b`
+  --> $DIR/unused-imports-in-test-mode.rs:38:13
+   |
+LL |         use crate::b;
+   |             ^^^^^^^^
+
+error: unused import: `super::a`
+  --> $DIR/unused-imports-in-test-mode.rs:43:9
+   |
+LL |     use super::a;
+   |         ^^^^^^^^
+
+error: unused import: `crate::b`
+  --> $DIR/unused-imports-in-test-mode.rs:46:13
+   |
+LL |         use crate::b;
+   |             ^^^^^^^^
+
+error: unused import: `super::a`
+  --> $DIR/unused-imports-in-test-mode.rs:51:9
+   |
+LL |     use super::a;
+   |         ^^^^^^^^
+
+error: unused import: `crate::b`
+  --> $DIR/unused-imports-in-test-mode.rs:54:13
+   |
+LL |         use crate::b;
+   |             ^^^^^^^^
+
+error: unused import: `super::a`
+  --> $DIR/unused-imports-in-test-mode.rs:59:9
+   |
+LL |     use super::a;
+   |         ^^^^^^^^
+
+error: unused import: `crate::b`
+  --> $DIR/unused-imports-in-test-mode.rs:62:13
+   |
+LL |         use crate::b;
+   |             ^^^^^^^^
+
+error: unused import: `super::a`
+  --> $DIR/unused-imports-in-test-mode.rs:68:9
+   |
+LL |     use super::a;
+   |         ^^^^^^^^
+
+error: unused import: `crate::b`
+  --> $DIR/unused-imports-in-test-mode.rs:71:13
+   |
+LL |         use crate::b;
+   |             ^^^^^^^^
+
+error: unused import: `super::a`
+  --> $DIR/unused-imports-in-test-mode.rs:77:9
+   |
+LL |     use super::a;
+   |         ^^^^^^^^
+
+error: unused import: `crate::b`
+  --> $DIR/unused-imports-in-test-mode.rs:80:13
+   |
+LL |         use crate::b;
+   |             ^^^^^^^^
+
+error: aborting due to 19 previous errors
+