resolve: Use `feature(custom_attribute)` fallback only if the feature is enabled

Normally `#![feature(...)]` shouldn't change behavior, but custom attributes in particular are in the process of retirement, and we should not produce a message telling to enable them.
It also helps with unifying diagnostics for unresolved macros.

42 files changed, 144 insertions, 379 deletions

diff --git a/src/librustc_resolve/diagnostics.rs b/src/librustc_resolve/diagnostics.rs
index 0159b8c5bb4..424ebbbd88d 100644
--- a/src/librustc_resolve/diagnostics.rs
+++ b/src/librustc_resolve/diagnostics.rs
@@ -11,7 +11,6 @@ use rustc::ty::{self, DefIdTree};
 use rustc::util::nodemap::FxHashSet;
 use syntax::ast::{self, Expr, ExprKind, Ident, NodeId, Path, Ty, TyKind};
 use syntax::ext::base::MacroKind;
-use syntax::feature_gate::{feature_err, AttributeGate, GateIssue, Stability, BUILTIN_ATTRIBUTES};
 use syntax::symbol::{Symbol, kw};
 use syntax::util::lev_distance::find_best_match_for_name;
 use syntax_pos::{BytePos, Span};
@@ -903,60 +902,6 @@ impl<'a> Resolver<'a> {
             }
         }
     }
-
-    crate fn report_unknown_attribute(&self, span: Span, name: &str, msg: &str, feature: Symbol) {
-        let mut err = feature_err(
-            &self.session.parse_sess,
-            feature,
-            span,
-            GateIssue::Language,
-            &msg,
-        );
-
-        let features = self.session.features_untracked();
-
-        let attr_candidates = BUILTIN_ATTRIBUTES
-            .iter()
-            .filter_map(|&(name, _, _, ref gate)| {
-                if name.as_str().starts_with("rustc_") && !features.rustc_attrs {
-                    return None;
-                }
-
-                match gate {
-                    AttributeGate::Gated(Stability::Unstable, ..)
-                        if self.session.opts.unstable_features.is_nightly_build() =>
-                    {
-                        Some(name)
-                    }
-                    AttributeGate::Gated(Stability::Deprecated(..), ..) => Some(name),
-                    AttributeGate::Ungated => Some(name),
-                    _ => None,
-                }
-            })
-            .chain(
-                // Add built-in macro attributes as well.
-                self.builtin_macros.iter().filter_map(|(name, binding)| {
-                    match binding.macro_kind() {
-                        Some(MacroKind::Attr) => Some(*name),
-                        _ => None,
-                    }
-                }),
-            )
-            .collect::<Vec<_>>();
-
-        let lev_suggestion = find_best_match_for_name(attr_candidates.iter(), &name, None);
-
-        if let Some(suggestion) = lev_suggestion {
-            err.span_suggestion(
-                span,
-                "a built-in attribute with a similar name exists",
-                suggestion.to_string(),
-                Applicability::MaybeIncorrect,
-            );
-        }
-
-        err.emit();
-    }
 }
 
 impl<'a, 'b> ImportResolver<'a, 'b> {
diff --git a/src/librustc_resolve/macros.rs b/src/librustc_resolve/macros.rs
index bc10d230dbd..bf1c4d671c6 100644
--- a/src/librustc_resolve/macros.rs
+++ b/src/librustc_resolve/macros.rs
@@ -312,23 +312,7 @@ impl<'a> Resolver<'a> {
                     }
                 }
             }
-            Res::NonMacroAttr(attr_kind) => {
-                if attr_kind == NonMacroAttrKind::Custom {
-                    assert!(path.segments.len() == 1);
-                    if !features.custom_attribute {
-                        let msg = format!("The attribute `{}` is currently unknown to the \
-                                            compiler and may have meaning added to it in the \
-                                            future", path);
-                        self.report_unknown_attribute(
-                            path.span,
-                            &path.segments[0].ident.as_str(),
-                            &msg,
-                            sym::custom_attribute,
-                        );
-                    }
-                }
-            }
-            Res::Err => {}
+            Res::NonMacroAttr(..) | Res::Err => {}
             _ => panic!("expected `DefKind::Macro` or `Res::NonMacroAttr`"),
         };
 
@@ -721,7 +705,8 @@ impl<'a> Resolver<'a> {
         }
 
         let determinacy = Determinacy::determined(determinacy == Determinacy::Determined || force);
-        if determinacy == Determinacy::Determined && macro_kind == Some(MacroKind::Attr) {
+        if determinacy == Determinacy::Determined && macro_kind == Some(MacroKind::Attr) &&
+           self.session.features_untracked().custom_attribute {
             // For single-segment attributes interpret determinate "no resolution" as a custom
             // attribute. (Lexical resolution implies the first segment and attr kind should imply
             // the last segment, so we are certainly working with a single-segment attribute here.)
diff --git a/src/test/ui/attributes/obsolete-attr.rs b/src/test/ui/attributes/obsolete-attr.rs
index 89e2ad2669c..8759344e6f8 100644
--- a/src/test/ui/attributes/obsolete-attr.rs
+++ b/src/test/ui/attributes/obsolete-attr.rs
@@ -1,7 +1,9 @@
 // Obsolete attributes fall back to feature gated custom attributes.
 
-#[ab_isize="stdcall"] extern {} //~ ERROR attribute `ab_isize` is currently unknown
+#[ab_isize="stdcall"] extern {}
+//~^ ERROR cannot find attribute macro `ab_isize` in this scope
 
-#[fixed_stack_segment] fn f() {} //~ ERROR attribute `fixed_stack_segment` is currently unknown
+#[fixed_stack_segment] fn f() {}
+//~^ ERROR cannot find attribute macro `fixed_stack_segment` in this scope
 
 fn main() {}
diff --git a/src/test/ui/attributes/obsolete-attr.stderr b/src/test/ui/attributes/obsolete-attr.stderr
index 6021700dfbb..9c6909f65f3 100644
--- a/src/test/ui/attributes/obsolete-attr.stderr
+++ b/src/test/ui/attributes/obsolete-attr.stderr
@@ -1,21 +1,14 @@
-error[E0658]: The attribute `fixed_stack_segment` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/obsolete-attr.rs:5:3
+error: cannot find attribute macro `fixed_stack_segment` in this scope
+  --> $DIR/obsolete-attr.rs:6:3
    |
 LL | #[fixed_stack_segment] fn f() {}
    |   ^^^^^^^^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `ab_isize` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `ab_isize` in this scope
   --> $DIR/obsolete-attr.rs:3:3
    |
 LL | #[ab_isize="stdcall"] extern {}
    |   ^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/attributes/unknown-attr.rs b/src/test/ui/attributes/unknown-attr.rs
index e2a4f3226d5..140a1fc3f93 100644
--- a/src/test/ui/attributes/unknown-attr.rs
+++ b/src/test/ui/attributes/unknown-attr.rs
@@ -2,8 +2,11 @@
 
 #![feature(custom_inner_attributes)]
 
-#![mutable_doc] //~ ERROR attribute `mutable_doc` is currently unknown
+#![mutable_doc]
+//~^ ERROR cannot find attribute macro `mutable_doc` in this scope
 
-#[dance] mod a {} //~ ERROR attribute `dance` is currently unknown
+#[dance] mod a {}
+//~^ ERROR cannot find attribute macro `dance` in this scope
 
-#[dance] fn main() {} //~ ERROR attribute `dance` is currently unknown
+#[dance] fn main() {}
+//~^ ERROR cannot find attribute macro `dance` in this scope
diff --git a/src/test/ui/attributes/unknown-attr.stderr b/src/test/ui/attributes/unknown-attr.stderr
index b46db566293..4d463874d66 100644
--- a/src/test/ui/attributes/unknown-attr.stderr
+++ b/src/test/ui/attributes/unknown-attr.stderr
@@ -1,30 +1,20 @@
-error[E0658]: The attribute `mutable_doc` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `mutable_doc` in this scope
   --> $DIR/unknown-attr.rs:5:4
    |
 LL | #![mutable_doc]
    |    ^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `dance` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/unknown-attr.rs:7:3
+error: cannot find attribute macro `dance` in this scope
+  --> $DIR/unknown-attr.rs:8:3
    |
 LL | #[dance] mod a {}
    |   ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `dance` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/unknown-attr.rs:9:3
+error: cannot find attribute macro `dance` in this scope
+  --> $DIR/unknown-attr.rs:11:3
    |
 LL | #[dance] fn main() {}
    |   ^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
 error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.rs b/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.rs
index 1ed2ddcda44..22dbac76670 100644
--- a/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.rs
+++ b/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.rs
@@ -1,6 +1,7 @@
 macro_rules! foo {
     () => {
-        #[cfg_attr(all(), unknown)] //~ ERROR `unknown` is currently unknown
+        #[cfg_attr(all(), unknown)]
+        //~^ ERROR cannot find attribute macro `unknown` in this scope
         fn foo() {}
     }
 }
diff --git a/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.stderr b/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.stderr
index cf4d0fc5ad0..c7c52a2923a 100644
--- a/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.stderr
+++ b/src/test/ui/conditional-compilation/cfg-attr-unknown-attribute-macro-expansion.stderr
@@ -1,4 +1,4 @@
-error[E0658]: The attribute `unknown` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `unknown` in this scope
   --> $DIR/cfg-attr-unknown-attribute-macro-expansion.rs:3:27
    |
 LL |         #[cfg_attr(all(), unknown)]
@@ -6,10 +6,6 @@ LL |         #[cfg_attr(all(), unknown)]
 ...
 LL | foo!();
    | ------- in this macro invocation
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/custom_attribute.rs b/src/test/ui/custom_attribute.rs
index 9cb43ab07ad..13c873c3b7e 100644
--- a/src/test/ui/custom_attribute.rs
+++ b/src/test/ui/custom_attribute.rs
@@ -1,9 +1,9 @@
 #![feature(stmt_expr_attributes)]
 
-#[foo] //~ ERROR The attribute `foo`
+#[foo] //~ ERROR cannot find attribute macro `foo` in this scope
 fn main() {
-    #[foo] //~ ERROR The attribute `foo`
+    #[foo] //~ ERROR cannot find attribute macro `foo` in this scope
     let x = ();
-    #[foo] //~ ERROR The attribute `foo`
+    #[foo] //~ ERROR cannot find attribute macro `foo` in this scope
     x
 }
diff --git a/src/test/ui/custom_attribute.stderr b/src/test/ui/custom_attribute.stderr
index 84c4e33e55a..b4f9f3f49b2 100644
--- a/src/test/ui/custom_attribute.stderr
+++ b/src/test/ui/custom_attribute.stderr
@@ -1,30 +1,20 @@
-error[E0658]: The attribute `foo` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `foo` in this scope
   --> $DIR/custom_attribute.rs:3:3
    |
 LL | #[foo]
    |   ^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `foo` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `foo` in this scope
   --> $DIR/custom_attribute.rs:5:7
    |
 LL |     #[foo]
    |       ^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `foo` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `foo` in this scope
   --> $DIR/custom_attribute.rs:7:7
    |
 LL |     #[foo]
    |       ^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
 error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/feature-gates/feature-gate-custom_attribute.rs b/src/test/ui/feature-gates/feature-gate-custom_attribute.rs
index f31c9d5afc4..d34936b42a6 100644
--- a/src/test/ui/feature-gates/feature-gate-custom_attribute.rs
+++ b/src/test/ui/feature-gates/feature-gate-custom_attribute.rs
@@ -1,23 +1,18 @@
 // Check that literals in attributes parse just fine.
 
+#[fake_attr] //~ ERROR cannot find attribute macro `fake_attr` in this scope
+#[fake_attr(100)] //~ ERROR cannot find attribute macro `fake_attr` in this scope
+#[fake_attr(1, 2, 3)] //~ ERROR cannot find attribute macro `fake_attr` in this scope
+#[fake_attr("hello")] //~ ERROR cannot find attribute macro `fake_attr` in this scope
+#[fake_attr(name = "hello")] //~ ERROR cannot find attribute macro `fake_attr` in this scope
+#[fake_attr(1, "hi", key = 12, true, false)] //~ ERROR cannot find attribute macro `fake_attr` in th
+#[fake_attr(key = "hello", val = 10)] //~ ERROR cannot find attribute macro `fake_attr` in this scop
+#[fake_attr(key("hello"), val(10))] //~ ERROR cannot find attribute macro `fake_attr` in this scope
+#[fake_attr(enabled = true, disabled = false)] //~ ERROR cannot find attribute macro `fake_attr` in
+#[fake_attr(true)] //~ ERROR cannot find attribute macro `fake_attr` in this scope
+#[fake_attr(pi = 3.14159)] //~ ERROR cannot find attribute macro `fake_attr` in this scope
+#[fake_attr(b"hi")] //~ ERROR cannot find attribute macro `fake_attr` in this scope
+#[fake_doc(r"doc")] //~ ERROR cannot find attribute macro `fake_doc` in this scope
+struct Q {}
 
-#![allow(dead_code)]
-#![allow(unused_variables)]
-
-#[fake_attr] //~ ERROR attribute `fake_attr` is currently unknown
-#[fake_attr(100)] //~ ERROR attribute `fake_attr` is currently unknown
-#[fake_attr(1, 2, 3)] //~ ERROR attribute `fake_attr` is currently unknown
-#[fake_attr("hello")] //~ ERROR attribute `fake_attr` is currently unknown
-#[fake_attr(name = "hello")] //~ ERROR attribute `fake_attr` is currently unknown
-#[fake_attr(1, "hi", key = 12, true, false)] //~ ERROR attribute `fake_attr` is currently unknown
-#[fake_attr(key = "hello", val = 10)] //~ ERROR attribute `fake_attr` is currently unknown
-#[fake_attr(key("hello"), val(10))] //~ ERROR attribute `fake_attr` is currently unknown
-#[fake_attr(enabled = true, disabled = false)] //~ ERROR attribute `fake_attr` is currently unknown
-#[fake_attr(true)] //~ ERROR attribute `fake_attr` is currently unknown
-#[fake_attr(pi = 3.14159)] //~ ERROR attribute `fake_attr` is currently unknown
-#[fake_attr(b"hi")] //~ ERROR attribute `fake_attr` is currently unknown
-#[fake_doc(r"doc")] //~ ERROR attribute `fake_doc` is currently unknown
-struct Q {  }
-
-
-fn main() { }
+fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-custom_attribute.stderr b/src/test/ui/feature-gates/feature-gate-custom_attribute.stderr
index 12175feadd6..efdc2d1cd31 100644
--- a/src/test/ui/feature-gates/feature-gate-custom_attribute.stderr
+++ b/src/test/ui/feature-gates/feature-gate-custom_attribute.stderr
@@ -1,120 +1,80 @@
-error[E0658]: The attribute `fake_attr` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute.rs:7:3
+error: cannot find attribute macro `fake_attr` in this scope
+  --> $DIR/feature-gate-custom_attribute.rs:3:3
    |
 LL | #[fake_attr]
    |   ^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `fake_attr` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute.rs:8:3
+error: cannot find attribute macro `fake_attr` in this scope
+  --> $DIR/feature-gate-custom_attribute.rs:4:3
    |
 LL | #[fake_attr(100)]
    |   ^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `fake_attr` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute.rs:9:3
+error: cannot find attribute macro `fake_attr` in this scope
+  --> $DIR/feature-gate-custom_attribute.rs:5:3
    |
 LL | #[fake_attr(1, 2, 3)]
    |   ^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `fake_attr` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute.rs:10:3
+error: cannot find attribute macro `fake_attr` in this scope
+  --> $DIR/feature-gate-custom_attribute.rs:6:3
    |
 LL | #[fake_attr("hello")]
    |   ^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `fake_attr` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute.rs:11:3
+error: cannot find attribute macro `fake_attr` in this scope
+  --> $DIR/feature-gate-custom_attribute.rs:7:3
    |
 LL | #[fake_attr(name = "hello")]
    |   ^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `fake_attr` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute.rs:12:3
+error: cannot find attribute macro `fake_attr` in this scope
+  --> $DIR/feature-gate-custom_attribute.rs:8:3
    |
 LL | #[fake_attr(1, "hi", key = 12, true, false)]
    |   ^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `fake_attr` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute.rs:13:3
+error: cannot find attribute macro `fake_attr` in this scope
+  --> $DIR/feature-gate-custom_attribute.rs:9:3
    |
 LL | #[fake_attr(key = "hello", val = 10)]
    |   ^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `fake_attr` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute.rs:14:3
+error: cannot find attribute macro `fake_attr` in this scope
+  --> $DIR/feature-gate-custom_attribute.rs:10:3
    |
 LL | #[fake_attr(key("hello"), val(10))]
    |   ^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `fake_attr` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute.rs:15:3
+error: cannot find attribute macro `fake_attr` in this scope
+  --> $DIR/feature-gate-custom_attribute.rs:11:3
    |
 LL | #[fake_attr(enabled = true, disabled = false)]
    |   ^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `fake_attr` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute.rs:16:3
+error: cannot find attribute macro `fake_attr` in this scope
+  --> $DIR/feature-gate-custom_attribute.rs:12:3
    |
 LL | #[fake_attr(true)]
    |   ^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `fake_attr` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute.rs:17:3
+error: cannot find attribute macro `fake_attr` in this scope
+  --> $DIR/feature-gate-custom_attribute.rs:13:3
    |
 LL | #[fake_attr(pi = 3.14159)]
    |   ^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `fake_attr` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute.rs:18:3
+error: cannot find attribute macro `fake_attr` in this scope
+  --> $DIR/feature-gate-custom_attribute.rs:14:3
    |
 LL | #[fake_attr(b"hi")]
    |   ^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `fake_doc` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/feature-gate-custom_attribute.rs:19:3
+error: cannot find attribute macro `fake_doc` in this scope
+  --> $DIR/feature-gate-custom_attribute.rs:15:3
    |
 LL | #[fake_doc(r"doc")]
    |   ^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
 error: aborting due to 13 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/feature-gates/feature-gate-rustc-attrs.rs b/src/test/ui/feature-gates/feature-gate-rustc-attrs.rs
index 9ce2fb58ab0..13983726c78 100644
--- a/src/test/ui/feature-gates/feature-gate-rustc-attrs.rs
+++ b/src/test/ui/feature-gates/feature-gate-rustc-attrs.rs
@@ -19,5 +19,5 @@ fn g() {}
 //~^ ERROR used by the test suite
 #[rustc_unknown]
 //~^ ERROR attributes starting with `rustc` are reserved for use by the `rustc` compiler
-//~| ERROR attribute `rustc_unknown` is currently unknown
+//~| ERROR cannot find attribute macro `rustc_unknown` in this scope
 fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-rustc-attrs.stderr b/src/test/ui/feature-gates/feature-gate-rustc-attrs.stderr
index 7c5aa5381e8..23cf936ee83 100644
--- a/src/test/ui/feature-gates/feature-gate-rustc-attrs.stderr
+++ b/src/test/ui/feature-gates/feature-gate-rustc-attrs.stderr
@@ -37,14 +37,11 @@ LL | #[rustc_unknown]
    = note: for more information, see https://github.com/rust-lang/rust/issues/29642
    = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
 
-error[E0658]: The attribute `rustc_unknown` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `rustc_unknown` in this scope
   --> $DIR/feature-gate-rustc-attrs.rs:20:3
    |
 LL | #[rustc_unknown]
    |   ^^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
 error[E0658]: used by the test suite
   --> $DIR/feature-gate-rustc-attrs.rs:18:1
diff --git a/src/test/ui/issues/issue-32655.rs b/src/test/ui/issues/issue-32655.rs
index 4634179d4e1..fad7bf55cf4 100644
--- a/src/test/ui/issues/issue-32655.rs
+++ b/src/test/ui/issues/issue-32655.rs
@@ -1,9 +1,6 @@
-#![allow(dead_code)]
-#![feature(rustc_attrs)]
-
 macro_rules! foo (
     () => (
-        #[derive_Clone] //~ ERROR attribute `derive_Clone` is currently unknown
+        #[derive_Clone] //~ ERROR cannot find attribute macro `derive_Clone` in this scope
         struct T;
     );
 );
@@ -15,7 +12,7 @@ macro_rules! bar (
 foo!();
 
 bar!(
-    #[derive_Clone] //~ ERROR attribute `derive_Clone` is currently unknown
+    #[derive_Clone] //~ ERROR cannot find attribute macro `derive_Clone` in this scope
     struct S;
 );
 
diff --git a/src/test/ui/issues/issue-32655.stderr b/src/test/ui/issues/issue-32655.stderr
index 43bb4105c8d..e13bed0fbfd 100644
--- a/src/test/ui/issues/issue-32655.stderr
+++ b/src/test/ui/issues/issue-32655.stderr
@@ -1,24 +1,17 @@
-error[E0658]: The attribute `derive_Clone` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/issue-32655.rs:6:11
+error: cannot find attribute macro `derive_Clone` in this scope
+  --> $DIR/issue-32655.rs:3:11
    |
 LL |         #[derive_Clone]
    |           ^^^^^^^^^^^^
 ...
 LL | foo!();
    | ------- in this macro invocation
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `derive_Clone` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/issue-32655.rs:18:7
+error: cannot find attribute macro `derive_Clone` in this scope
+  --> $DIR/issue-32655.rs:15:7
    |
 LL |     #[derive_Clone]
    |       ^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/issues/issue-49074.rs b/src/test/ui/issues/issue-49074.rs
index ad66e421c6b..38074d5b05c 100644
--- a/src/test/ui/issues/issue-49074.rs
+++ b/src/test/ui/issues/issue-49074.rs
@@ -1,7 +1,7 @@
 // Check that unknown attribute error is shown even if there are unresolved macros.
 
 #[marco_use] // typo
-//~^ ERROR The attribute `marco_use` is currently unknown to the compiler
+//~^ ERROR cannot find attribute macro `marco_use` in this scope
 mod foo {
     macro_rules! bar {
         () => ();
diff --git a/src/test/ui/issues/issue-49074.stderr b/src/test/ui/issues/issue-49074.stderr
index 3ab876dbf42..d9b133a8c57 100644
--- a/src/test/ui/issues/issue-49074.stderr
+++ b/src/test/ui/issues/issue-49074.stderr
@@ -1,11 +1,8 @@
-error[E0658]: The attribute `marco_use` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `marco_use` in this scope
   --> $DIR/issue-49074.rs:3:3
    |
 LL | #[marco_use] // typo
-   |   ^^^^^^^^^ help: a built-in attribute with a similar name exists: `macro_use`
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+   |   ^^^^^^^^^
 
 error: cannot find macro `bar!` in this scope
   --> $DIR/issue-49074.rs:12:4
@@ -17,4 +14,3 @@ LL |    bar!();
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/macros/macro-reexport-removed.rs b/src/test/ui/macros/macro-reexport-removed.rs
index fb33794a5ca..b69a1fa4df0 100644
--- a/src/test/ui/macros/macro-reexport-removed.rs
+++ b/src/test/ui/macros/macro-reexport-removed.rs
@@ -2,7 +2,7 @@
 
 #![feature(macro_reexport)] //~ ERROR feature has been removed
 
-#[macro_reexport(macro_one)] //~ ERROR attribute `macro_reexport` is currently unknown
+#[macro_reexport(macro_one)] //~ ERROR cannot find attribute macro `macro_reexport` in this scope
 extern crate two_macros;
 
 fn main() {}
diff --git a/src/test/ui/macros/macro-reexport-removed.stderr b/src/test/ui/macros/macro-reexport-removed.stderr
index 44233d7b7dd..29baa6e0f28 100644
--- a/src/test/ui/macros/macro-reexport-removed.stderr
+++ b/src/test/ui/macros/macro-reexport-removed.stderr
@@ -10,16 +10,12 @@ note: subsumed by `pub use`
 LL | #![feature(macro_reexport)]
    |            ^^^^^^^^^^^^^^
 
-error[E0658]: The attribute `macro_reexport` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `macro_reexport` in this scope
   --> $DIR/macro-reexport-removed.rs:5:3
    |
 LL | #[macro_reexport(macro_one)]
-   |   ^^^^^^^^^^^^^^ help: a built-in attribute with a similar name exists: `macro_export`
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+   |   ^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0557, E0658.
-For more information about an error, try `rustc --explain E0557`.
+For more information about this error, try `rustc --explain E0557`.
diff --git a/src/test/ui/proc-macro/derive-helper-shadowing.rs b/src/test/ui/proc-macro/derive-helper-shadowing.rs
index cdc0d6da946..59ba1390e13 100644
--- a/src/test/ui/proc-macro/derive-helper-shadowing.rs
+++ b/src/test/ui/proc-macro/derive-helper-shadowing.rs
@@ -19,7 +19,7 @@ struct S {
         struct U;
 
         mod inner {
-            #[empty_helper] //~ ERROR attribute `empty_helper` is currently unknown
+            #[empty_helper] //~ ERROR cannot find attribute macro `empty_helper` in this scope
             struct V;
         }
 
diff --git a/src/test/ui/proc-macro/derive-helper-shadowing.stderr b/src/test/ui/proc-macro/derive-helper-shadowing.stderr
index 984ea4fb8ad..149f6eef443 100644
--- a/src/test/ui/proc-macro/derive-helper-shadowing.stderr
+++ b/src/test/ui/proc-macro/derive-helper-shadowing.stderr
@@ -1,11 +1,8 @@
-error[E0658]: The attribute `empty_helper` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `empty_helper` in this scope
   --> $DIR/derive-helper-shadowing.rs:22:15
    |
 LL |             #[empty_helper]
    |               ^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
 error[E0659]: `empty_helper` is ambiguous (derive helper attribute vs any other name)
   --> $DIR/derive-helper-shadowing.rs:8:3
@@ -27,5 +24,4 @@ LL | use test_macros::empty_attr as empty_helper;
 
 error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0658, E0659.
-For more information about an error, try `rustc --explain E0658`.
+For more information about this error, try `rustc --explain E0659`.
diff --git a/src/test/ui/proc-macro/derive-still-gated.rs b/src/test/ui/proc-macro/derive-still-gated.rs
index d895d26f267..4e6f9b07220 100644
--- a/src/test/ui/proc-macro/derive-still-gated.rs
+++ b/src/test/ui/proc-macro/derive-still-gated.rs
@@ -3,7 +3,7 @@
 #[macro_use]
 extern crate test_macros;
 
-#[derive_Empty] //~ ERROR attribute `derive_Empty` is currently unknown
+#[derive_Empty] //~ ERROR cannot find attribute macro `derive_Empty` in this scope
 struct A;
 
 fn main() {}
diff --git a/src/test/ui/proc-macro/derive-still-gated.stderr b/src/test/ui/proc-macro/derive-still-gated.stderr
index a6c0ce6260a..4df1715db94 100644
--- a/src/test/ui/proc-macro/derive-still-gated.stderr
+++ b/src/test/ui/proc-macro/derive-still-gated.stderr
@@ -1,12 +1,8 @@
-error[E0658]: The attribute `derive_Empty` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `derive_Empty` in this scope
   --> $DIR/derive-still-gated.rs:6:3
    |
 LL | #[derive_Empty]
    |   ^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/proc-macro/expand-to-unstable-2.rs b/src/test/ui/proc-macro/expand-to-unstable-2.rs
index 437ae930934..da7c89fdd46 100644
--- a/src/test/ui/proc-macro/expand-to-unstable-2.rs
+++ b/src/test/ui/proc-macro/expand-to-unstable-2.rs
@@ -1,11 +1,12 @@
 // aux-build:derive-unstable-2.rs
 
+#![feature(custom_attribute)]
+
 #[macro_use]
 extern crate derive_unstable_2;
 
 #[derive(Unstable)]
 //~^ ERROR attributes starting with `rustc` are reserved for use by the `rustc` compiler
-//~| ERROR attribute `rustc_foo` is currently unknown to the compiler
 
 struct A;
 
diff --git a/src/test/ui/proc-macro/expand-to-unstable-2.stderr b/src/test/ui/proc-macro/expand-to-unstable-2.stderr
index 3a729846d78..01e6a4a8ab9 100644
--- a/src/test/ui/proc-macro/expand-to-unstable-2.stderr
+++ b/src/test/ui/proc-macro/expand-to-unstable-2.stderr
@@ -1,5 +1,5 @@
 error[E0658]: attributes starting with `rustc` are reserved for use by the `rustc` compiler
-  --> $DIR/expand-to-unstable-2.rs:6:10
+  --> $DIR/expand-to-unstable-2.rs:8:10
    |
 LL | #[derive(Unstable)]
    |          ^^^^^^^^
@@ -7,15 +7,6 @@ LL | #[derive(Unstable)]
    = note: for more information, see https://github.com/rust-lang/rust/issues/29642
    = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
 
-error[E0658]: The attribute `rustc_foo` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/expand-to-unstable-2.rs:6:10
-   |
-LL | #[derive(Unstable)]
-   |          ^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/proc-macro/issue-41211.rs b/src/test/ui/proc-macro/issue-41211.rs
index ee9246e1c9b..491b89b2f55 100644
--- a/src/test/ui/proc-macro/issue-41211.rs
+++ b/src/test/ui/proc-macro/issue-41211.rs
@@ -3,11 +3,11 @@
 // FIXME: https://github.com/rust-lang/rust/issues/41430
 // This is a temporary regression test for the ICE reported in #41211
 
+#![feature(custom_attribute)]
 #![feature(custom_inner_attributes)]
 
 #![identity_attr]
-//~^ ERROR attribute `identity_attr` is currently unknown to the compiler
-//~| ERROR inconsistent resolution for a macro: first custom attribute, then attribute macro
+//~^ ERROR inconsistent resolution for a macro: first custom attribute, then attribute macro
 extern crate test_macros;
 use test_macros::identity_attr;
 
diff --git a/src/test/ui/proc-macro/issue-41211.stderr b/src/test/ui/proc-macro/issue-41211.stderr
index b5c08587e19..f01cba0c930 100644
--- a/src/test/ui/proc-macro/issue-41211.stderr
+++ b/src/test/ui/proc-macro/issue-41211.stderr
@@ -1,18 +1,8 @@
-error[E0658]: The attribute `identity_attr` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/issue-41211.rs:8:4
-   |
-LL | #![identity_attr]
-   |    ^^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
-
 error: inconsistent resolution for a macro: first custom attribute, then attribute macro
-  --> $DIR/issue-41211.rs:8:4
+  --> $DIR/issue-41211.rs:9:4
    |
 LL | #![identity_attr]
    |    ^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/proc-macro/macro-namespace-reserved-2.rs b/src/test/ui/proc-macro/macro-namespace-reserved-2.rs
index 7a9e472c6c3..8a26df9e76a 100644
--- a/src/test/ui/proc-macro/macro-namespace-reserved-2.rs
+++ b/src/test/ui/proc-macro/macro-namespace-reserved-2.rs
@@ -35,7 +35,7 @@ fn check_bang3() {
                        //~| ERROR expected macro, found derive macro `crate::MyTrait`
 }
 
-#[my_macro] //~ ERROR attribute `my_macro` is currently unknown
+#[my_macro] //~ ERROR cannot find attribute macro `my_macro` in this scope
 #[crate::my_macro] //~ ERROR can't use a procedural macro from the same crate that defines it
                    //~| ERROR expected attribute, found macro `crate::my_macro`
 fn check_attr1() {}
diff --git a/src/test/ui/proc-macro/macro-namespace-reserved-2.stderr b/src/test/ui/proc-macro/macro-namespace-reserved-2.stderr
index 8a5e346c2b5..e6017dc4d11 100644
--- a/src/test/ui/proc-macro/macro-namespace-reserved-2.stderr
+++ b/src/test/ui/proc-macro/macro-namespace-reserved-2.stderr
@@ -76,15 +76,6 @@ error: can't use a procedural macro from the same crate that defines it
 LL | #[derive(MyTrait)]
    |          ^^^^^^^
 
-error[E0658]: The attribute `my_macro` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/macro-namespace-reserved-2.rs:38:3
-   |
-LL | #[my_macro]
-   |   ^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
-
 error: can't use a procedural macro from the same crate that defines it
   --> $DIR/macro-namespace-reserved-2.rs:39:3
    |
@@ -97,6 +88,12 @@ error: expected attribute, found macro `crate::my_macro`
 LL | #[crate::my_macro]
    |   ^^^^^^^^^^^^^^^ not an attribute
 
+error: cannot find attribute macro `my_macro` in this scope
+  --> $DIR/macro-namespace-reserved-2.rs:38:3
+   |
+LL | #[my_macro]
+   |   ^^^^^^^^
+
 error: cannot find derive macro `my_macro` in this scope
   --> $DIR/macro-namespace-reserved-2.rs:48:10
    |
@@ -117,4 +114,3 @@ LL |     MyTrait!();
 
 error: aborting due to 19 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/proc-macro/proc-macro-attributes.rs b/src/test/ui/proc-macro/proc-macro-attributes.rs
index 062053453ee..04215226c6d 100644
--- a/src/test/ui/proc-macro/proc-macro-attributes.rs
+++ b/src/test/ui/proc-macro/proc-macro-attributes.rs
@@ -4,7 +4,7 @@
 extern crate derive_b;
 
 #[B] //~ ERROR `B` is ambiguous
-#[C] //~ ERROR attribute `C` is currently unknown to the compiler
+#[C] //~ ERROR cannot find attribute macro `C` in this scope
 #[B(D)] //~ ERROR `B` is ambiguous
 #[B(E = "foo")] //~ ERROR `B` is ambiguous
 #[B(arbitrary tokens)] //~ ERROR `B` is ambiguous
diff --git a/src/test/ui/proc-macro/proc-macro-attributes.stderr b/src/test/ui/proc-macro/proc-macro-attributes.stderr
index 02dfce1a735..f59a47ad294 100644
--- a/src/test/ui/proc-macro/proc-macro-attributes.stderr
+++ b/src/test/ui/proc-macro/proc-macro-attributes.stderr
@@ -1,11 +1,8 @@
-error[E0658]: The attribute `C` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `C` in this scope
   --> $DIR/proc-macro-attributes.rs:7:3
    |
 LL | #[C]
    |   ^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
 error[E0659]: `B` is ambiguous (derive helper attribute vs any other name)
   --> $DIR/proc-macro-attributes.rs:6:3
@@ -77,5 +74,4 @@ LL | #[macro_use]
 
 error: aborting due to 5 previous errors
 
-Some errors have detailed explanations: E0658, E0659.
-For more information about an error, try `rustc --explain E0658`.
+For more information about this error, try `rustc --explain E0659`.
diff --git a/src/test/ui/proc-macro/resolve-error.rs b/src/test/ui/proc-macro/resolve-error.rs
index 1298c08df84..0a7861aba6e 100644
--- a/src/test/ui/proc-macro/resolve-error.rs
+++ b/src/test/ui/proc-macro/resolve-error.rs
@@ -24,11 +24,11 @@ macro_rules! attr_proc_mac {
 struct Foo;
 
 // Interpreted as a feature gated custom attribute
-#[attr_proc_macra] //~ ERROR attribute `attr_proc_macra` is currently unknown
+#[attr_proc_macra] //~ ERROR cannot find attribute macro `attr_proc_macra` in this scope
 struct Bar;
 
 // Interpreted as a feature gated custom attribute
-#[FooWithLongNan] //~ ERROR attribute `FooWithLongNan` is currently unknown
+#[FooWithLongNan] //~ ERROR cannot find attribute macro `FooWithLongNan` in this scope
 struct Asdf;
 
 #[derive(Dlone)]
diff --git a/src/test/ui/proc-macro/resolve-error.stderr b/src/test/ui/proc-macro/resolve-error.stderr
index 02cf7cdb964..ca13fc2003c 100644
--- a/src/test/ui/proc-macro/resolve-error.stderr
+++ b/src/test/ui/proc-macro/resolve-error.stderr
@@ -1,26 +1,20 @@
-error[E0658]: The attribute `attr_proc_macra` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find derive macro `FooWithLongNan` in this scope
+  --> $DIR/resolve-error.rs:22:10
+   |
+LL | #[derive(FooWithLongNan)]
+   |          ^^^^^^^^^^^^^^ help: try: `FooWithLongName`
+
+error: cannot find attribute macro `attr_proc_macra` in this scope
   --> $DIR/resolve-error.rs:27:3
    |
 LL | #[attr_proc_macra]
-   |   ^^^^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+   |   ^^^^^^^^^^^^^^^ help: try: `attr_proc_macro`
 
-error[E0658]: The attribute `FooWithLongNan` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `FooWithLongNan` in this scope
   --> $DIR/resolve-error.rs:31:3
    |
 LL | #[FooWithLongNan]
    |   ^^^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
-
-error: cannot find derive macro `FooWithLongNan` in this scope
-  --> $DIR/resolve-error.rs:22:10
-   |
-LL | #[derive(FooWithLongNan)]
-   |          ^^^^^^^^^^^^^^ help: try: `FooWithLongName`
 
 error: cannot find derive macro `Dlone` in this scope
   --> $DIR/resolve-error.rs:34:10
@@ -66,4 +60,3 @@ LL |     bang_proc_macrp!();
 
 error: aborting due to 10 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/reserved/reserved-attr-on-macro.rs b/src/test/ui/reserved/reserved-attr-on-macro.rs
index cb535362266..fddb991da82 100644
--- a/src/test/ui/reserved/reserved-attr-on-macro.rs
+++ b/src/test/ui/reserved/reserved-attr-on-macro.rs
@@ -1,5 +1,5 @@
 #[rustc_attribute_should_be_reserved]
-//~^ ERROR attribute `rustc_attribute_should_be_reserved` is currently unknown
+//~^ ERROR cannot find attribute macro `rustc_attribute_should_be_reserved` in this scope
 //~| ERROR attributes starting with `rustc` are reserved for use by the `rustc` compiler
 
 macro_rules! foo {
diff --git a/src/test/ui/reserved/reserved-attr-on-macro.stderr b/src/test/ui/reserved/reserved-attr-on-macro.stderr
index cbd111b47bf..d4b97d290ea 100644
--- a/src/test/ui/reserved/reserved-attr-on-macro.stderr
+++ b/src/test/ui/reserved/reserved-attr-on-macro.stderr
@@ -7,14 +7,11 @@ LL | #[rustc_attribute_should_be_reserved]
    = note: for more information, see https://github.com/rust-lang/rust/issues/29642
    = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
 
-error[E0658]: The attribute `rustc_attribute_should_be_reserved` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `rustc_attribute_should_be_reserved` in this scope
   --> $DIR/reserved-attr-on-macro.rs:1:3
    |
 LL | #[rustc_attribute_should_be_reserved]
    |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
 error: cannot determine resolution for the macro `foo`
   --> $DIR/reserved-attr-on-macro.rs:10:5
diff --git a/src/test/ui/span/issue-36530.rs b/src/test/ui/span/issue-36530.rs
index e11be9e17f2..14b2c8644e0 100644
--- a/src/test/ui/span/issue-36530.rs
+++ b/src/test/ui/span/issue-36530.rs
@@ -1,9 +1,10 @@
 // gate-test-custom_inner_attributes
 
-#[foo] //~ ERROR is currently unknown to the compiler
+#![feature(custom_attribute)]
+
+#[foo]
 mod foo {
-    #![foo] //~ ERROR is currently unknown to the compiler
-            //~| ERROR non-builtin inner attributes are unstable
+    #![foo] //~ ERROR non-builtin inner attributes are unstable
 }
 
 fn main() {}
diff --git a/src/test/ui/span/issue-36530.stderr b/src/test/ui/span/issue-36530.stderr
index 65f03e756a2..c6b7895e65a 100644
--- a/src/test/ui/span/issue-36530.stderr
+++ b/src/test/ui/span/issue-36530.stderr
@@ -1,14 +1,5 @@
-error[E0658]: The attribute `foo` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/issue-36530.rs:3:3
-   |
-LL | #[foo]
-   |   ^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
-
 error[E0658]: non-builtin inner attributes are unstable
-  --> $DIR/issue-36530.rs:5:5
+  --> $DIR/issue-36530.rs:7:5
    |
 LL |     #![foo]
    |     ^^^^^^^
@@ -16,15 +7,6 @@ LL |     #![foo]
    = note: for more information, see https://github.com/rust-lang/rust/issues/54726
    = help: add `#![feature(custom_inner_attributes)]` to the crate attributes to enable
 
-error[E0658]: The attribute `foo` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/issue-36530.rs:5:8
-   |
-LL |     #![foo]
-   |        ^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
-
-error: aborting due to 3 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/suggestions/attribute-typos.rs b/src/test/ui/suggestions/attribute-typos.rs
index 0e10131ce8d..74f63f2b0ed 100644
--- a/src/test/ui/suggestions/attribute-typos.rs
+++ b/src/test/ui/suggestions/attribute-typos.rs
@@ -1,11 +1,11 @@
-#[deprcated] //~ ERROR attribute `deprcated` is currently unknown
+#[deprcated] //~ ERROR cannot find attribute macro `deprcated` in this scope
 fn foo() {}
 
-#[tests] //~ ERROR attribute `tests` is currently unknown to the compiler
+#[tests] //~ ERROR cannot find attribute macro `tests` in this scope
 fn bar() {}
 
 #[rustc_err]
-//~^ ERROR attribute `rustc_err` is currently unknown
+//~^ ERROR cannot find attribute macro `rustc_err` in this scope
 //~| ERROR attributes starting with `rustc` are reserved for use by the `rustc` compiler
 
 fn main() {}
diff --git a/src/test/ui/suggestions/attribute-typos.stderr b/src/test/ui/suggestions/attribute-typos.stderr
index 7c28e882728..8ed9eef05c8 100644
--- a/src/test/ui/suggestions/attribute-typos.stderr
+++ b/src/test/ui/suggestions/attribute-typos.stderr
@@ -7,32 +7,23 @@ LL | #[rustc_err]
    = note: for more information, see https://github.com/rust-lang/rust/issues/29642
    = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
 
-error[E0658]: The attribute `rustc_err` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `rustc_err` in this scope
   --> $DIR/attribute-typos.rs:7:3
    |
 LL | #[rustc_err]
    |   ^^^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
 
-error[E0658]: The attribute `tests` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `tests` in this scope
   --> $DIR/attribute-typos.rs:4:3
    |
 LL | #[tests]
-   |   ^^^^^ help: a built-in attribute with a similar name exists: `test`
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+   |   ^^^^^ help: try: `test`
 
-error[E0658]: The attribute `deprcated` is currently unknown to the compiler and may have meaning added to it in the future
+error: cannot find attribute macro `deprcated` in this scope
   --> $DIR/attribute-typos.rs:1:3
    |
 LL | #[deprcated]
-   |   ^^^^^^^^^ help: a built-in attribute with a similar name exists: `deprecated`
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
+   |   ^^^^^^^^^
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/tool-attributes/tool-attributes-misplaced-1.rs b/src/test/ui/tool-attributes/tool-attributes-misplaced-1.rs
index ce902b7e7d2..8c62b34bd9e 100644
--- a/src/test/ui/tool-attributes/tool-attributes-misplaced-1.rs
+++ b/src/test/ui/tool-attributes/tool-attributes-misplaced-1.rs
@@ -5,7 +5,7 @@ type B = rustfmt::skip; //~ ERROR expected type, found tool attribute `rustfmt::
 struct S;
 
 // Interpreted as a feature gated custom attribute
-#[rustfmt] //~ ERROR attribute `rustfmt` is currently unknown
+#[rustfmt] //~ ERROR cannot find attribute macro `rustfmt` in this scope
 fn check() {}
 
 #[rustfmt::skip] // OK
diff --git a/src/test/ui/tool-attributes/tool-attributes-misplaced-1.stderr b/src/test/ui/tool-attributes/tool-attributes-misplaced-1.stderr
index 32c9a1e8b6e..33581a17082 100644
--- a/src/test/ui/tool-attributes/tool-attributes-misplaced-1.stderr
+++ b/src/test/ui/tool-attributes/tool-attributes-misplaced-1.stderr
@@ -1,18 +1,15 @@
-error[E0658]: The attribute `rustfmt` is currently unknown to the compiler and may have meaning added to it in the future
-  --> $DIR/tool-attributes-misplaced-1.rs:8:3
-   |
-LL | #[rustfmt]
-   |   ^^^^^^^
-   |
-   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
-   = help: add `#![feature(custom_attribute)]` to the crate attributes to enable
-
 error: cannot find derive macro `rustfmt` in this scope
   --> $DIR/tool-attributes-misplaced-1.rs:4:10
    |
 LL | #[derive(rustfmt)]
    |          ^^^^^^^
 
+error: cannot find attribute macro `rustfmt` in this scope
+  --> $DIR/tool-attributes-misplaced-1.rs:8:3
+   |
+LL | #[rustfmt]
+   |   ^^^^^^^
+
 error: cannot find macro `rustfmt!` in this scope
   --> $DIR/tool-attributes-misplaced-1.rs:14:5
    |
@@ -45,5 +42,4 @@ LL |     rustfmt::skip;
 
 error: aborting due to 7 previous errors
 
-Some errors have detailed explanations: E0423, E0658.
-For more information about an error, try `rustc --explain E0423`.
+For more information about this error, try `rustc --explain E0423`.