Updated error message for accidental uses of derive attribute as a crate attribute

compiler/rustc_passes/src/check_attr.rs

@@ -1953,28 +1953,52 @@ fn is_c_like_enum(item: &Item<'_>) -> bool {
     }
 }
 
+// FIXME: Fix "Cannot determine resolution" error and remove built-in macros
+// from this check.
 fn check_invalid_crate_level_attr(tcx: TyCtxt<'_>, attrs: &[Attribute]) {
+    // Check for builtin attributes at the crate level
+    // which were unsuccessfully resolved due to cannot determine
+    // resolution for the attribute macro error.
     const ATTRS_TO_CHECK: &[Symbol] = &[
         sym::macro_export,
         sym::repr,
         sym::path,
         sym::automatically_derived,
         sym::start,
         sym::rustc_main,
+        sym::derive,
+        sym::test,
+        sym::test_case,
+        sym::global_allocator,
+        sym::bench,
     ];
 
     for attr in attrs {
-        for attr_to_check in ATTRS_TO_CHECK {
-            if attr.has_name(*attr_to_check) {
-                tcx.sess
-                    .struct_span_err(
+        // This function should only be called with crate attributes
+        // which are inner attributes always but lets check to make sure
+        if attr.style == AttrStyle::Inner {
+            for attr_to_check in ATTRS_TO_CHECK {
+                if attr.has_name(*attr_to_check) {
+                    let mut err = tcx.sess.struct_span_err(
                         attr.span,
                         &format!(
                             "`{}` attribute cannot be used at crate level",
                             attr_to_check.to_ident_string()
                         ),
-                    )
-                    .emit();
+                    );
+                    // Only emit an error with a suggestion if we can create a
+                    // string out of the attribute span
+                    if let Ok(src) = tcx.sess.source_map().span_to_snippet(attr.span) {
+                        let replacement = src.replace("#!", "#");
+                        err.span_suggestion_verbose(
+                            attr.span,
+                            "perhaps you meant to use an outer attribute",
+                            replacement,
+                            rustc_errors::Applicability::MachineApplicable,
+                        );
+                    }
+                    err.emit()
+                }
             }
         }
     }

src/test/ui/derives/issue-36617.rs

@@ -1,3 +1,16 @@
 #![derive(Copy)] //~ ERROR cannot determine resolution for the attribute macro `derive`
+//~^ ERROR `derive` attribute cannot be used at crate level
+
+#![test]//~ ERROR cannot determine resolution for the attribute macro `test`
+//~^ ERROR `test` attribute cannot be used at crate level
+
+#![test_case]//~ ERROR cannot determine resolution for the attribute macro `test_case`
+//~^ ERROR `test_case` attribute cannot be used at crate level
+
+#![bench]//~ ERROR cannot determine resolution for the attribute macro `bench`
+//~^ ERROR `bench` attribute cannot be used at crate level
+
+#![global_allocator]//~ ERROR cannot determine resolution for the attribute macro `global_allocator`
+//~^ ERROR `global_allocator` attribute cannot be used at crate level
 
 fn main() {}

src/test/ui/derives/issue-36617.stderr

@@ -6,5 +6,92 @@ LL | #![derive(Copy)]
    |
    = note: import resolution is stuck, try simplifying macro imports
 
-error: aborting due to previous error
+error: cannot determine resolution for the attribute macro `test`
+  --> $DIR/issue-36617.rs:4:4
+   |
+LL | #![test]
+   |    ^^^^
+   |
+   = note: import resolution is stuck, try simplifying macro imports
+
+error: cannot determine resolution for the attribute macro `test_case`
+  --> $DIR/issue-36617.rs:7:4
+   |
+LL | #![test_case]
+   |    ^^^^^^^^^
+   |
+   = note: import resolution is stuck, try simplifying macro imports
+
+error: cannot determine resolution for the attribute macro `bench`
+  --> $DIR/issue-36617.rs:10:4
+   |
+LL | #![bench]
+   |    ^^^^^
+   |
+   = note: import resolution is stuck, try simplifying macro imports
+
+error: cannot determine resolution for the attribute macro `global_allocator`
+  --> $DIR/issue-36617.rs:13:4
+   |
+LL | #![global_allocator]
+   |    ^^^^^^^^^^^^^^^^
+   |
+   = note: import resolution is stuck, try simplifying macro imports
+
+error: `derive` attribute cannot be used at crate level
+  --> $DIR/issue-36617.rs:1:1
+   |
+LL | #![derive(Copy)]
+   | ^^^^^^^^^^^^^^^^
+   |
+help: perhaps you meant to use an outer attribute
+   |
+LL | #[derive(Copy)]
+   | ~~~~~~~~~~~~~~~
+
+error: `test` attribute cannot be used at crate level
+  --> $DIR/issue-36617.rs:4:1
+   |
+LL | #![test]
+   | ^^^^^^^^
+   |
+help: perhaps you meant to use an outer attribute
+   |
+LL | #[test]
+   | ~~~~~~~
+
+error: `test_case` attribute cannot be used at crate level
+  --> $DIR/issue-36617.rs:7:1
+   |
+LL | #![test_case]
+   | ^^^^^^^^^^^^^
+   |
+help: perhaps you meant to use an outer attribute
+   |
+LL | #[test_case]
+   | ~~~~~~~~~~~~
+
+error: `bench` attribute cannot be used at crate level
+  --> $DIR/issue-36617.rs:10:1
+   |
+LL | #![bench]
+   | ^^^^^^^^^
+   |
+help: perhaps you meant to use an outer attribute
+   |
+LL | #[bench]
+   | ~~~~~~~~
+
+error: `global_allocator` attribute cannot be used at crate level
+  --> $DIR/issue-36617.rs:13:1
+   |
+LL | #![global_allocator]
+   | ^^^^^^^^^^^^^^^^^^^^
+   |
+help: perhaps you meant to use an outer attribute
+   |
+LL | #[global_allocator]
+   | ~~~~~~~~~~~~~~~~~~~
+
+error: aborting due to 10 previous errors
 

src/test/ui/feature-gates/issue-43106-gating-of-bench.rs

@@ -6,5 +6,5 @@
 
 #![bench                   = "4100"]
 //~^ ERROR cannot determine resolution for the attribute macro `bench`
-
+//~^^ ERROR `bench` attribute cannot be used at crate level
 fn main() {}

src/test/ui/feature-gates/issue-43106-gating-of-bench.stderr

@@ -6,5 +6,16 @@ LL | #![bench                   = "4100"]
    |
    = note: import resolution is stuck, try simplifying macro imports
 
-error: aborting due to previous error
+error: `bench` attribute cannot be used at crate level
+  --> $DIR/issue-43106-gating-of-bench.rs:7:1
+   |
+LL | #![bench                   = "4100"]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: perhaps you meant to use an outer attribute
+   |
+LL | #[bench                   = "4100"]
+   |
+
+error: aborting due to 2 previous errors
 

src/test/ui/feature-gates/issue-43106-gating-of-builtin-attrs-error.stderr

@@ -129,36 +129,66 @@ error: `macro_export` attribute cannot be used at crate level
    |
 LL | #![macro_export]
    | ^^^^^^^^^^^^^^^^
+   |
+help: perhaps you meant to use an outer attribute
+   |
+LL | #[macro_export]
+   |
 
 error: `rustc_main` attribute cannot be used at crate level
   --> $DIR/issue-43106-gating-of-builtin-attrs-error.rs:14:1
    |
 LL | #![rustc_main]
    | ^^^^^^^^^^^^^^
+   |
+help: perhaps you meant to use an outer attribute
+   |
+LL | #[rustc_main]
+   | ~~~~~~~~~~~~~
 
 error: `start` attribute cannot be used at crate level
   --> $DIR/issue-43106-gating-of-builtin-attrs-error.rs:16:1
    |
 LL | #![start]
    | ^^^^^^^^^
+   |
+help: perhaps you meant to use an outer attribute
+   |
+LL | #[start]
+   |
 
 error: `repr` attribute cannot be used at crate level
   --> $DIR/issue-43106-gating-of-builtin-attrs-error.rs:18:1
    |
 LL | #![repr()]
    | ^^^^^^^^^^
+   |
+help: perhaps you meant to use an outer attribute
+   |
+LL | #[repr()]
+   |
 
 error: `path` attribute cannot be used at crate level
   --> $DIR/issue-43106-gating-of-builtin-attrs-error.rs:20:1
    |
 LL | #![path = "3800"]
    | ^^^^^^^^^^^^^^^^^
+   |
+help: perhaps you meant to use an outer attribute
+   |
+LL | #[path = "3800"]
+   |
 
 error: `automatically_derived` attribute cannot be used at crate level
   --> $DIR/issue-43106-gating-of-builtin-attrs-error.rs:22:1
    |
 LL | #![automatically_derived]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: perhaps you meant to use an outer attribute
+   |
+LL | #[automatically_derived]
+   |
 
 error[E0518]: attribute should be applied to function or closure
   --> $DIR/issue-43106-gating-of-builtin-attrs-error.rs:36:17

src/test/ui/feature-gates/issue-43106-gating-of-test.rs

@@ -3,5 +3,5 @@
 #![allow(soft_unstable)]
 #![test                    = "4200"]
 //~^ ERROR cannot determine resolution for the attribute macro `test`
-
+//~^^ ERROR `test` attribute cannot be used at crate level
 fn main() {}

src/test/ui/feature-gates/issue-43106-gating-of-test.stderr

@@ -6,5 +6,16 @@ LL | #![test                    = "4200"]
    |
    = note: import resolution is stuck, try simplifying macro imports
 
-error: aborting due to previous error
+error: `test` attribute cannot be used at crate level
+  --> $DIR/issue-43106-gating-of-test.rs:4:1
+   |
+LL | #![test                    = "4200"]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: perhaps you meant to use an outer attribute
+   |
+LL | #[test                    = "4200"]
+   |
+
+error: aborting due to 2 previous errors
 

src/test/ui/imports/issue-28134.rs

@@ -2,3 +2,4 @@
 
 #![allow(soft_unstable)]
 #![test] //~ ERROR cannot determine resolution for the attribute macro `test`
+//~^ ERROR 4:1: 4:9: `test` attribute cannot be used at crate level

src/test/ui/imports/issue-28134.stderr

@@ -6,5 +6,16 @@ LL | #![test]
    |
    = note: import resolution is stuck, try simplifying macro imports
 
-error: aborting due to previous error
+error: `test` attribute cannot be used at crate level
+  --> $DIR/issue-28134.rs:4:1
+   |
+LL | #![test]
+   | ^^^^^^^^
+   |
+help: perhaps you meant to use an outer attribute
+   |
+LL | #[test]
+   | ~~~~~~~
+
+error: aborting due to 2 previous errors
 

src/test/ui/span/issue-43927-non-ADT-derive.rs

@@ -1,5 +1,6 @@
 #![derive(Debug, PartialEq, Eq)] // should be an outer attribute!
 //~^ ERROR cannot determine resolution for the attribute macro `derive`
+//~^^ ERROR `derive` attribute cannot be used at crate level
 struct DerivedOn;
 
 fn main() {}

src/test/ui/span/issue-43927-non-ADT-derive.stderr

@@ -6,5 +6,16 @@ LL | #![derive(Debug, PartialEq, Eq)] // should be an outer attribute!
    |
    = note: import resolution is stuck, try simplifying macro imports
 
-error: aborting due to previous error
+error: `derive` attribute cannot be used at crate level
+  --> $DIR/issue-43927-non-ADT-derive.rs:1:1
+   |
+LL | #![derive(Debug, PartialEq, Eq)] // should be an outer attribute!
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: perhaps you meant to use an outer attribute
+   |
+LL | #[derive(Debug, PartialEq, Eq)] // should be an outer attribute!
+   | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+error: aborting due to 2 previous errors