Auto merge of #53471 - petrochenkov:biattr2, r=oli-obk

resolve: Some macro resolution refactoring

Work towards completing https://github.com/rust-lang/rust/pull/50911#issuecomment-411605393

The last commit also fixes https://github.com/rust-lang/rust/issues/53269 by not using `def_id()` on `Def::Err` and also fixes https://github.com/rust-lang/rust/issues/53512.

src/test/compile-fail-fulldeps/proc-macro/proc-macro-gates.rs

@@ -22,7 +22,7 @@ extern crate proc_macro_gates as foo;
 
 use foo::*;
 
-#[foo::a] //~ ERROR: paths of length greater than one
+#[foo::a] //~ ERROR: non-ident attribute macro paths are unstable
 fn _test() {}
 
 fn _test_inner() {

src/test/ui-fulldeps/proc-macro/macro-namespace-reserved-2.stderr

@@ -2,37 +2,37 @@ error: can't use a procedural macro from the same crate that defines it
   --> $DIR/macro-namespace-reserved-2.rs:34:5
    |
 LL |     my_macro!(); //~ ERROR can't use a procedural macro from the same crate that defines it
-   |     ^^^^^^^^^^^^
+   |     ^^^^^^^^
 
 error: can't use a procedural macro from the same crate that defines it
   --> $DIR/macro-namespace-reserved-2.rs:37:5
    |
 LL |     my_macro_attr!(); //~ ERROR can't use a procedural macro from the same crate that defines it
-   |     ^^^^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^
 
 error: can't use a procedural macro from the same crate that defines it
   --> $DIR/macro-namespace-reserved-2.rs:40:5
    |
 LL |     MyTrait!(); //~ ERROR can't use a procedural macro from the same crate that defines it
-   |     ^^^^^^^^^^^
+   |     ^^^^^^^
 
 error: can't use a procedural macro from the same crate that defines it
-  --> $DIR/macro-namespace-reserved-2.rs:43:1
+  --> $DIR/macro-namespace-reserved-2.rs:43:3
    |
 LL | #[my_macro] //~ ERROR can't use a procedural macro from the same crate that defines it
-   | ^^^^^^^^^^^
+   |   ^^^^^^^^
 
 error: can't use a procedural macro from the same crate that defines it
-  --> $DIR/macro-namespace-reserved-2.rs:45:1
+  --> $DIR/macro-namespace-reserved-2.rs:45:3
    |
 LL | #[my_macro_attr] //~ ERROR can't use a procedural macro from the same crate that defines it
-   | ^^^^^^^^^^^^^^^^
+   |   ^^^^^^^^^^^^^
 
 error: can't use a procedural macro from the same crate that defines it
-  --> $DIR/macro-namespace-reserved-2.rs:47:1
+  --> $DIR/macro-namespace-reserved-2.rs:47:3
    |
 LL | #[MyTrait] //~ ERROR can't use a procedural macro from the same crate that defines it
-   | ^^^^^^^^^^
+   |   ^^^^^^^
 
 error: can't use a procedural macro from the same crate that defines it
   --> $DIR/macro-namespace-reserved-2.rs:50:10

src/test/ui/cfg-attr-unknown-attribute-macro-expansion.stderr

@@ -2,7 +2,7 @@ error[E0658]: The attribute `unknown` is currently unknown to the compiler and m
   --> $DIR/cfg-attr-unknown-attribute-macro-expansion.rs:13:27
    |
 LL |         #[cfg_attr(all(), unknown)] //~ ERROR `unknown` is currently unknown
-   |                           ^^^^^^^^
+   |                           ^^^^^^^
 ...
 LL | foo!();
    | ------- in this macro invocation

src/test/ui/custom_attribute.stderr

@@ -1,24 +1,24 @@
 error[E0658]: The attribute `foo` is currently unknown to the compiler and may have meaning added to it in the future (see issue #29642)
-  --> $DIR/custom_attribute.rs:13:1
+  --> $DIR/custom_attribute.rs:13:3
    |
 LL | #[foo] //~ ERROR The attribute `foo`
-   | ^^^^^^
+   |   ^^^
    |
    = 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 (see issue #29642)
-  --> $DIR/custom_attribute.rs:15:5
+  --> $DIR/custom_attribute.rs:15:7
    |
 LL |     #[foo] //~ ERROR The attribute `foo`
-   |     ^^^^^^
+   |       ^^^
    |
    = 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 (see issue #29642)
-  --> $DIR/custom_attribute.rs:17:5
+  --> $DIR/custom_attribute.rs:17:7
    |
 LL |     #[foo] //~ ERROR The attribute `foo`
-   |     ^^^^^^
+   |       ^^^
    |
    = help: add #![feature(custom_attribute)] to the crate attributes to enable
 

src/test/ui/feature-gates/feature-gate-custom_attribute.stderr

@@ -1,104 +1,104 @@
 error[E0658]: The attribute `fake_attr` is currently unknown to the compiler and may have meaning added to it in the future (see issue #29642)
-  --> $DIR/feature-gate-custom_attribute.rs:17:1
+  --> $DIR/feature-gate-custom_attribute.rs:17:3
    |
 LL | #[fake_attr] //~ ERROR attribute `fake_attr` is currently unknown
-   | ^^^^^^^^^^^^
+   |   ^^^^^^^^^
    |
    = 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 (see issue #29642)
-  --> $DIR/feature-gate-custom_attribute.rs:18:1
+  --> $DIR/feature-gate-custom_attribute.rs:18:3
    |
 LL | #[fake_attr(100)] //~ ERROR attribute `fake_attr` is currently unknown
-   | ^^^^^^^^^^^^^^^^^
+   |   ^^^^^^^^^
    |
    = 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 (see issue #29642)
-  --> $DIR/feature-gate-custom_attribute.rs:19:1
+  --> $DIR/feature-gate-custom_attribute.rs:19:3
    |
 LL | #[fake_attr(1, 2, 3)] //~ ERROR attribute `fake_attr` is currently unknown
-   | ^^^^^^^^^^^^^^^^^^^^^
+   |   ^^^^^^^^^
    |
    = 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 (see issue #29642)
-  --> $DIR/feature-gate-custom_attribute.rs:20:1
+  --> $DIR/feature-gate-custom_attribute.rs:20:3
    |
 LL | #[fake_attr("hello")] //~ ERROR attribute `fake_attr` is currently unknown
-   | ^^^^^^^^^^^^^^^^^^^^^
+   |   ^^^^^^^^^
    |
    = 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 (see issue #29642)
-  --> $DIR/feature-gate-custom_attribute.rs:21:1
+  --> $DIR/feature-gate-custom_attribute.rs:21:3
    |
 LL | #[fake_attr(name = "hello")] //~ ERROR attribute `fake_attr` is currently unknown
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |   ^^^^^^^^^
    |
    = 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 (see issue #29642)
-  --> $DIR/feature-gate-custom_attribute.rs:22:1
+  --> $DIR/feature-gate-custom_attribute.rs:22:3
    |
 LL | #[fake_attr(1, "hi", key = 12, true, false)] //~ ERROR attribute `fake_attr` is currently unknown
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |   ^^^^^^^^^
    |
    = 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 (see issue #29642)
-  --> $DIR/feature-gate-custom_attribute.rs:23:1
+  --> $DIR/feature-gate-custom_attribute.rs:23:3
    |
 LL | #[fake_attr(key = "hello", val = 10)] //~ ERROR attribute `fake_attr` is currently unknown
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |   ^^^^^^^^^
    |
    = 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 (see issue #29642)
-  --> $DIR/feature-gate-custom_attribute.rs:24:1
+  --> $DIR/feature-gate-custom_attribute.rs:24:3
    |
 LL | #[fake_attr(key("hello"), val(10))] //~ ERROR attribute `fake_attr` is currently unknown
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |   ^^^^^^^^^
    |
    = 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 (see issue #29642)
-  --> $DIR/feature-gate-custom_attribute.rs:25:1
+  --> $DIR/feature-gate-custom_attribute.rs:25:3
    |
 LL | #[fake_attr(enabled = true, disabled = false)] //~ ERROR attribute `fake_attr` is currently unknown
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |   ^^^^^^^^^
    |
    = 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 (see issue #29642)
-  --> $DIR/feature-gate-custom_attribute.rs:26:1
+  --> $DIR/feature-gate-custom_attribute.rs:26:3
    |
 LL | #[fake_attr(true)] //~ ERROR attribute `fake_attr` is currently unknown
-   | ^^^^^^^^^^^^^^^^^^
+   |   ^^^^^^^^^
    |
    = 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 (see issue #29642)
-  --> $DIR/feature-gate-custom_attribute.rs:27:1
+  --> $DIR/feature-gate-custom_attribute.rs:27:3
    |
 LL | #[fake_attr(pi = 3.14159)] //~ ERROR attribute `fake_attr` is currently unknown
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |   ^^^^^^^^^
    |
    = 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 (see issue #29642)
-  --> $DIR/feature-gate-custom_attribute.rs:28:1
+  --> $DIR/feature-gate-custom_attribute.rs:28:3
    |
 LL | #[fake_attr(b"hi")] //~ ERROR attribute `fake_attr` is currently unknown
-   | ^^^^^^^^^^^^^^^^^^^
+   |   ^^^^^^^^^
    |
    = 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 (see issue #29642)
-  --> $DIR/feature-gate-custom_attribute.rs:29:1
+  --> $DIR/feature-gate-custom_attribute.rs:29:3
    |
 LL | #[fake_doc(r"doc")] //~ ERROR attribute `fake_doc` is currently unknown
-   | ^^^^^^^^^^^^^^^^^^^
+   |   ^^^^^^^^
    |
    = help: add #![feature(custom_attribute)] to the crate attributes to enable
 

src/test/ui/feature-gates/feature-gate-custom_derive.stderr

@@ -1,8 +1,8 @@
 error[E0658]: attributes of the form `#[derive_*]` are reserved for the compiler (see issue #29644)
-  --> $DIR/feature-gate-custom_derive.rs:11:1
+  --> $DIR/feature-gate-custom_derive.rs:11:3
    |
 LL | #[derive_Clone]
-   | ^^^^^^^^^^^^^^^
+   |   ^^^^^^^^^^^^
    |
    = help: add #![feature(custom_derive)] to the crate attributes to enable
 

src/test/ui/feature-gates/feature-gate-rustc-attrs.stderr

@@ -1,8 +1,8 @@
 error[E0658]: unless otherwise specified, attributes with the prefix `rustc_` are reserved for internal compiler diagnostics (see issue #29642)
-  --> $DIR/feature-gate-rustc-attrs.rs:15:1
+  --> $DIR/feature-gate-rustc-attrs.rs:15:3
    |
 LL | #[rustc_foo]
-   | ^^^^^^^^^^^^
+   |   ^^^^^^^^^
    |
    = help: add #![feature(rustc_attrs)] to the crate attributes to enable
 

src/test/ui/feature-gates/feature-gate-tool_attributes.stderr

@@ -1,8 +1,8 @@
 error[E0658]: tool attributes are unstable (see issue #44690)
-  --> $DIR/feature-gate-tool_attributes.rs:12:5
+  --> $DIR/feature-gate-tool_attributes.rs:12:7
    |
 LL |     #[rustfmt::skip] //~ ERROR tool attributes are unstable
-   |     ^^^^^^^^^^^^^^^^
+   |       ^^^^^^^^^^^^^
    |
    = help: add #![feature(tool_attributes)] to the crate attributes to enable
 

src/test/ui/imports/issue-53269.rs

@@ -0,0 +1,21 @@
+// 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.
+
+// Ambiguity between a `macro_rules` macro and a non-existent import recovered as `Def::Err`
+
+macro_rules! mac { () => () }
+
+mod m {
+    use nonexistent_module::mac; //~ ERROR unresolved import `nonexistent_module`
+
+    mac!(); //~ ERROR `mac` is ambiguous
+}
+
+fn main() {}

src/test/ui/imports/issue-53269.stderr

@@ -0,0 +1,27 @@
+error[E0432]: unresolved import `nonexistent_module`
+  --> $DIR/issue-53269.rs:16:9
+   |
+LL |     use nonexistent_module::mac; //~ ERROR unresolved import `nonexistent_module`
+   |         ^^^^^^^^^^^^^^^^^^ Maybe a missing `extern crate nonexistent_module;`?
+
+error[E0659]: `mac` is ambiguous
+  --> $DIR/issue-53269.rs:18:5
+   |
+LL |     mac!(); //~ ERROR `mac` is ambiguous
+   |     ^^^
+   |
+note: `mac` could refer to the name defined here
+  --> $DIR/issue-53269.rs:13:1
+   |
+LL | macro_rules! mac { () => () }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+note: `mac` could also refer to the name imported here
+  --> $DIR/issue-53269.rs:16:9
+   |
+LL |     use nonexistent_module::mac; //~ ERROR unresolved import `nonexistent_module`
+   |         ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+Some errors occurred: E0432, E0659.
+For more information about an error, try `rustc --explain E0432`.

src/test/ui/imports/issue-53512.rs

@@ -0,0 +1,17 @@
+// 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.
+
+// Macro from prelude is shadowed by non-existent import recovered as `Def::Err`.
+
+use std::assert; //~ ERROR unresolved import `std::assert`
+
+fn main() {
+    assert!(true);
+}

src/test/ui/imports/issue-53512.stderr

@@ -0,0 +1,9 @@
+error[E0432]: unresolved import `std::assert`
+  --> $DIR/issue-53512.rs:13:5
+   |
+LL | use std::assert; //~ ERROR unresolved import `std::assert`
+   |     ^^^^^^^^^^^ no `assert` in the root
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0432`.

src/test/ui/imports/macros.stderr

@@ -1,15 +1,15 @@
-error: `m` is ambiguous
+error[E0659]: `m` is ambiguous
   --> $DIR/macros.rs:48:5
    |
 LL |     m!(); //~ ERROR ambiguous
    |     ^
    |
-note: `m` could refer to the macro defined here
+note: `m` could refer to the name defined here
   --> $DIR/macros.rs:46:5
    |
 LL |     macro_rules! m { () => {} }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
-note: `m` could also refer to the macro imported here
+note: `m` could also refer to the name imported here
   --> $DIR/macros.rs:47:9
    |
 LL |     use two_macros::m;

src/test/ui/imports/shadow_builtin_macros.rs

@@ -37,10 +37,10 @@ mod m4 {
 
 mod m5 {
     macro_rules! m { () => {
-        macro_rules! panic { () => {} } //~ ERROR `panic` is already in scope
+        macro_rules! panic { () => {} }
     } }
     m!();
-    panic!();
+    panic!(); //~ ERROR `panic` is ambiguous
 }
 
 #[macro_use(n)]

src/test/ui/imports/shadow_builtin_macros.stderr

@@ -1,13 +1,19 @@
-error: `panic` is already in scope
+error[E0659]: `panic` is ambiguous
+  --> $DIR/shadow_builtin_macros.rs:43:5
+   |
+LL |     panic!(); //~ ERROR `panic` is ambiguous
+   |     ^^^^^
+   |
+note: `panic` could refer to the name defined here
   --> $DIR/shadow_builtin_macros.rs:40:9
    |
-LL |         macro_rules! panic { () => {} } //~ ERROR `panic` is already in scope
+LL |         macro_rules! panic { () => {} }
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 LL |     } }
 LL |     m!();
    |     ----- in this macro invocation
-   |
-   = note: macro-expanded `macro_rules!`s may not shadow existing macros (see RFC 1560)
+   = note: `panic` is also a builtin macro
+   = note: macro-expanded macros do not shadow
 
 error[E0659]: `panic` is ambiguous
   --> $DIR/shadow_builtin_macros.rs:25:14

src/test/ui/issues/issue-32655.stderr

@@ -1,8 +1,8 @@
 error[E0658]: attributes of the form `#[derive_*]` are reserved for the compiler (see issue #29644)
-  --> $DIR/issue-32655.rs:16:9
+  --> $DIR/issue-32655.rs:16:11
    |
 LL |         #[derive_Clone] //~ ERROR attributes of the form
-   |         ^^^^^^^^^^^^^^^
+   |           ^^^^^^^^^^^^
 ...
 LL | foo!();
    | ------- in this macro invocation
@@ -10,10 +10,10 @@ LL | foo!();
    = help: add #![feature(custom_derive)] to the crate attributes to enable
 
 error[E0658]: attributes of the form `#[derive_*]` are reserved for the compiler (see issue #29644)
-  --> $DIR/issue-32655.rs:28:5
+  --> $DIR/issue-32655.rs:28:7
    |
 LL |     #[derive_Clone] //~ ERROR attributes of the form
-   |     ^^^^^^^^^^^^^^^
+   |       ^^^^^^^^^^^^
    |
    = help: add #![feature(custom_derive)] to the crate attributes to enable
 

src/test/ui/issues/issue-49074.stderr

@@ -1,8 +1,8 @@
 error[E0658]: The attribute `marco_use` is currently unknown to the compiler and may have meaning added to it in the future (see issue #29642)
-  --> $DIR/issue-49074.rs:13:1
+  --> $DIR/issue-49074.rs:13:3
    |
 LL | #[marco_use] // typo
-   | ^^^^^^^^^^^^
+   |   ^^^^^^^^^
    |
    = help: add #![feature(custom_attribute)] to the crate attributes to enable
 

src/test/ui/macros/macro-reexport-removed.stderr

@@ -11,10 +11,10 @@ LL | #![feature(macro_reexport)] //~ ERROR feature has been removed
    |            ^^^^^^^^^^^^^^
 
 error[E0658]: The attribute `macro_reexport` is currently unknown to the compiler and may have meaning added to it in the future (see issue #29642)
-  --> $DIR/macro-reexport-removed.rs:15:1
+  --> $DIR/macro-reexport-removed.rs:15:3
    |
 LL | #[macro_reexport(macro_one)] //~ ERROR attribute `macro_reexport` is currently unknown
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |   ^^^^^^^^^^^^^^
    |
    = help: add #![feature(custom_attribute)] to the crate attributes to enable
 

src/test/ui/reserved/reserved-attr-on-macro.stderr

@@ -1,8 +1,8 @@
 error[E0658]: unless otherwise specified, attributes with the prefix `rustc_` are reserved for internal compiler diagnostics (see issue #29642)
-  --> $DIR/reserved-attr-on-macro.rs:11:1
+  --> $DIR/reserved-attr-on-macro.rs:11:3
    |
 LL | #[rustc_attribute_should_be_reserved] //~ ERROR attributes with the prefix `rustc_` are reserved
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: add #![feature(rustc_attrs)] to the crate attributes to enable
 

src/test/ui/span/issue-36530.stderr

@@ -1,16 +1,16 @@
 error[E0658]: The attribute `foo` is currently unknown to the compiler and may have meaning added to it in the future (see issue #29642)
-  --> $DIR/issue-36530.rs:11:1
+  --> $DIR/issue-36530.rs:11:3
    |
 LL | #[foo] //~ ERROR is currently unknown to the compiler
-   | ^^^^^^
+   |   ^^^
    |
    = 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 (see issue #29642)
-  --> $DIR/issue-36530.rs:13:5
+  --> $DIR/issue-36530.rs:13:8
    |
 LL |     #![foo] //~ ERROR is currently unknown to the compiler
-   |     ^^^^^^^
+   |        ^^^
    |
    = help: add #![feature(custom_attribute)] to the crate attributes to enable