Auto merge of #53053 - petrochenkov:custattr, r=alexcrichton

resolve:  Support custom attributes when macro modularization is enabled

Basically, if resolution of a single-segment attribute is a determined error, then we interpret it as a custom attribute.

Since custom attributes are integrated into general macro resolution, `feature(custom_attribute)` now requires and implicitly enables macro modularization (`feature(use_extern_macros)`).
Actually, a few other "advanced" macro features now implicitly enable macro modularization too (and one bug was found and fixed in process of enabling it).

The first two commits are preliminary cleanups/refactorings.

src/test/ui/custom-attribute-multisegment.rs

@@ -0,0 +1,18 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Unresolved multi-segment attributes are not treated as custom.
+
+#![feature(custom_attribute, proc_macro_path_invoc)]
+
+mod existent {}
+
+#[existent::nonexistent] //~ ERROR failed to resolve. Could not find `nonexistent` in `existent`
+fn main() {}

src/test/ui/custom-attribute-multisegment.stderr

@@ -0,0 +1,9 @@
+error[E0433]: failed to resolve. Could not find `nonexistent` in `existent`
+  --> $DIR/custom-attribute-multisegment.rs:17:13
+   |
+LL | #[existent::nonexistent] //~ ERROR failed to resolve. Could not find `nonexistent` in `existent`
+   |             ^^^^^^^^^^^ Could not find `nonexistent` in `existent`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0433`.

src/test/ui/feature-gate-macros_in_extern.rs

@@ -27,9 +27,9 @@ macro_rules! emits_nothing(
 #[link(name = "rust_test_helpers", kind = "static")]
 extern {
     returns_isize!(rust_get_test_int);
-    //~^ ERROR macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro invocations in `extern {}` blocks are experimental
     takes_u32_returns_u32!(rust_dbg_extern_identity_u32);
-    //~^ ERROR macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro invocations in `extern {}` blocks are experimental
     emits_nothing!();
-    //~^ ERROR macro invocations in `extern {}` blocks are experimental.
+    //~^ ERROR macro invocations in `extern {}` blocks are experimental
 }

src/test/ui/feature-gate-macros_in_extern.stderr

@@ -1,4 +1,4 @@
-error[E0658]: macro and proc-macro invocations in `extern {}` blocks are experimental. (see issue #49476)
+error[E0658]: macro invocations in `extern {}` blocks are experimental (see issue #49476)
   --> $DIR/feature-gate-macros_in_extern.rs:29:5
    |
 LL |     returns_isize!(rust_get_test_int);
@@ -6,7 +6,7 @@ LL |     returns_isize!(rust_get_test_int);
    |
    = help: add #![feature(macros_in_extern)] to the crate attributes to enable
 
-error[E0658]: macro and proc-macro invocations in `extern {}` blocks are experimental. (see issue #49476)
+error[E0658]: macro invocations in `extern {}` blocks are experimental (see issue #49476)
   --> $DIR/feature-gate-macros_in_extern.rs:31:5
    |
 LL |     takes_u32_returns_u32!(rust_dbg_extern_identity_u32);
@@ -14,7 +14,7 @@ LL |     takes_u32_returns_u32!(rust_dbg_extern_identity_u32);
    |
    = help: add #![feature(macros_in_extern)] to the crate attributes to enable
 
-error[E0658]: macro and proc-macro invocations in `extern {}` blocks are experimental. (see issue #49476)
+error[E0658]: macro invocations in `extern {}` blocks are experimental (see issue #49476)
   --> $DIR/feature-gate-macros_in_extern.rs:33:5
    |
 LL |     emits_nothing!();

src/test/ui/imports/macros.rs

@@ -10,7 +10,7 @@
 
 // aux-build:two_macros.rs
 
-#![feature(item_like_imports, use_extern_macros)]
+#![feature(use_extern_macros)]
 
 extern crate two_macros; // two identity macros `m` and `n`
 

src/test/ui/issue-11692-2.rs

@@ -10,5 +10,5 @@
 
 fn main() {
     concat!(test!());
-    //~^ ERROR expected a macro, found non-macro attribute
+    //~^ ERROR expected a macro, found built-in attribute
 }

src/test/ui/issue-11692-2.stderr

@@ -1,4 +1,4 @@
-error: expected a macro, found non-macro attribute
+error: expected a macro, found built-in attribute
   --> $DIR/issue-11692-2.rs:12:13
    |
 LL |     concat!(test!());

src/test/ui/macro-path-prelude-fail-3.rs

@@ -10,9 +10,9 @@
 
 #![feature(use_extern_macros)]
 
-#[derive(inline)] //~ ERROR expected a macro, found non-macro attribute
+#[derive(inline)] //~ ERROR expected a macro, found built-in attribute
 struct S;
 
 fn main() {
-    inline!(); //~ ERROR expected a macro, found non-macro attribute
+    inline!(); //~ ERROR expected a macro, found built-in attribute
 }

src/test/ui/macro-path-prelude-fail-3.stderr

@@ -1,13 +1,13 @@
-error: expected a macro, found non-macro attribute
+error: expected a macro, found built-in attribute
   --> $DIR/macro-path-prelude-fail-3.rs:13:10
    |
-LL | #[derive(inline)] //~ ERROR expected a macro, found non-macro attribute
+LL | #[derive(inline)] //~ ERROR expected a macro, found built-in attribute
    |          ^^^^^^
 
-error: expected a macro, found non-macro attribute
+error: expected a macro, found built-in attribute
   --> $DIR/macro-path-prelude-fail-3.rs:17:5
    |
-LL |     inline!(); //~ ERROR expected a macro, found non-macro attribute
+LL |     inline!(); //~ ERROR expected a macro, found built-in attribute
    |     ^^^^^^
 
 error: aborting due to 2 previous errors

src/test/ui/tool-attributes-disabled-2.rs

@@ -11,9 +11,5 @@
 // If macro modularization (`use_extern_macros`) is not enabled,
 // then tool attributes are treated as custom attributes.
 
-// compile-pass
-
-#![feature(custom_attribute)]
-
-#[rustfmt::bar]
+#[rustfmt::bar] //~ ERROR attribute `rustfmt::bar` is currently unknown to the compiler
 fn main() {}

src/test/ui/tool-attributes-disabled-2.stderr

@@ -0,0 +1,11 @@
+error[E0658]: The attribute `rustfmt::bar` is currently unknown to the compiler and may have meaning added to it in the future (see issue #29642)
+  --> $DIR/tool-attributes-disabled-2.rs:14:1
+   |
+LL | #[rustfmt::bar] //~ ERROR attribute `rustfmt::bar` is currently unknown to the compiler
+   | ^^^^^^^^^^^^^^^
+   |
+   = 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`.

src/test/ui/tool-attributes-misplaced-1.rs

@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(tool_attributes)]
+#![feature(tool_attributes, custom_attribute)]
 
 type A = rustfmt; //~ ERROR expected type, found tool module `rustfmt`
-type B = rustfmt::skip; //~ ERROR expected type, found non-macro attribute `rustfmt::skip`
+type B = rustfmt::skip; //~ ERROR expected type, found tool attribute `rustfmt::skip`
 
 #[derive(rustfmt)] //~ ERROR cannot find derive macro `rustfmt` in this scope
 struct S;
 
-#[rustfmt] //~ ERROR cannot find attribute macro `rustfmt` in this scope
+#[rustfmt] // OK, interpreted as a custom attribute
 fn check() {}
 
 #[rustfmt::skip] // OK
@@ -24,5 +24,5 @@ fn main() {
     rustfmt; //~ ERROR expected value, found tool module `rustfmt`
     rustfmt!(); //~ ERROR cannot find macro `rustfmt!` in this scope
 
-    rustfmt::skip; //~ ERROR expected value, found non-macro attribute `rustfmt::skip`
+    rustfmt::skip; //~ ERROR expected value, found tool attribute `rustfmt::skip`
 }

src/test/ui/tool-attributes-misplaced-1.stderr

@@ -4,12 +4,6 @@ error: cannot find derive macro `rustfmt` in this scope
 LL | #[derive(rustfmt)] //~ ERROR cannot find derive macro `rustfmt` in this scope
    |          ^^^^^^^
 
-error: cannot find attribute macro `rustfmt` in this scope
-  --> $DIR/tool-attributes-misplaced-1.rs:19:3
-   |
-LL | #[rustfmt] //~ ERROR cannot find attribute macro `rustfmt` in this scope
-   |   ^^^^^^^
-
 error: cannot find macro `rustfmt!` in this scope
   --> $DIR/tool-attributes-misplaced-1.rs:25:5
    |
@@ -22,10 +16,10 @@ error[E0573]: expected type, found tool module `rustfmt`
 LL | type A = rustfmt; //~ ERROR expected type, found tool module `rustfmt`
    |          ^^^^^^^ not a type
 
-error[E0573]: expected type, found non-macro attribute `rustfmt::skip`
+error[E0573]: expected type, found tool attribute `rustfmt::skip`
   --> $DIR/tool-attributes-misplaced-1.rs:14:10
    |
-LL | type B = rustfmt::skip; //~ ERROR expected type, found non-macro attribute `rustfmt::skip`
+LL | type B = rustfmt::skip; //~ ERROR expected type, found tool attribute `rustfmt::skip`
    |          ^^^^^^^^^^^^^ not a type
 
 error[E0423]: expected value, found tool module `rustfmt`
@@ -34,13 +28,13 @@ error[E0423]: expected value, found tool module `rustfmt`
 LL |     rustfmt; //~ ERROR expected value, found tool module `rustfmt`
    |     ^^^^^^^ not a value
 
-error[E0423]: expected value, found non-macro attribute `rustfmt::skip`
+error[E0423]: expected value, found tool attribute `rustfmt::skip`
   --> $DIR/tool-attributes-misplaced-1.rs:27:5
    |
-LL |     rustfmt::skip; //~ ERROR expected value, found non-macro attribute `rustfmt::skip`
+LL |     rustfmt::skip; //~ ERROR expected value, found tool attribute `rustfmt::skip`
    |     ^^^^^^^^^^^^^ not a value
 
-error: aborting due to 7 previous errors
+error: aborting due to 6 previous errors
 
 Some errors occurred: E0423, E0573.
 For more information about an error, try `rustc --explain E0423`.

src/test/ui/tool-attributes-misplaced-2.rs

@@ -10,9 +10,9 @@
 
 #![feature(tool_attributes)]
 
-#[derive(rustfmt::skip)] //~ ERROR expected a macro, found non-macro attribute
+#[derive(rustfmt::skip)] //~ ERROR expected a macro, found tool attribute
 struct S;
 
 fn main() {
-    rustfmt::skip!(); //~ ERROR expected a macro, found non-macro attribute
+    rustfmt::skip!(); //~ ERROR expected a macro, found tool attribute
 }

src/test/ui/tool-attributes-misplaced-2.stderr

@@ -1,13 +1,13 @@
-error: expected a macro, found non-macro attribute
+error: expected a macro, found tool attribute
   --> $DIR/tool-attributes-misplaced-2.rs:13:10
    |
-LL | #[derive(rustfmt::skip)] //~ ERROR expected a macro, found non-macro attribute
+LL | #[derive(rustfmt::skip)] //~ ERROR expected a macro, found tool attribute
    |          ^^^^^^^^^^^^^
 
-error: expected a macro, found non-macro attribute
+error: expected a macro, found tool attribute
   --> $DIR/tool-attributes-misplaced-2.rs:17:5
    |
-LL |     rustfmt::skip!(); //~ ERROR expected a macro, found non-macro attribute
+LL |     rustfmt::skip!(); //~ ERROR expected a macro, found tool attribute
    |     ^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors