Improve Rustdoc's handling of procedural macros

Fixes #58700
Fixes #58696
Fixes #49553
Fixes #52210

This commit removes the special rustdoc handling for proc macros, as we
can now
retrieve their span and attributes just like any other item.

A new command-line option is added to rustdoc: `--crate-type`. This
takes the same options as rustc's `--crate-type` option. However, all
values other than `proc-macro` are treated the same. This allows Rustdoc
to enable 'proc macro mode' when handling a proc macro crate.

In compiletest, a new 'rustdoc-flags' option is added. This allows us to
pass in the '--proc-macro-crate' flag in the absence of Cargo.

I've opened [an additional PR to
Cargo](https://github.com/rust-lang/cargo/pull/7159) to support passing
in this flag.
These two PRS can be merged in any order - the Cargo changes will not
take effect until the 'cargo' submodule is updated in this repository.

4 files changed, 20 insertions, 10 deletions

diff --git a/src/test/rustdoc/inline_cross/auxiliary/proc_macro.rs b/src/test/rustdoc/inline_cross/auxiliary/proc_macro.rs
index c99ef744333..37465ccf1c2 100644
--- a/src/test/rustdoc/inline_cross/auxiliary/proc_macro.rs
+++ b/src/test/rustdoc/inline_cross/auxiliary/proc_macro.rs
@@ -1,5 +1,6 @@
 // force-host
 // no-prefer-dynamic
+// compile-flags: --crate-type proc-macro
 
 #![crate_type="proc-macro"]
 #![crate_name="some_macros"]
@@ -25,3 +26,9 @@ pub fn some_proc_attr(_attr: TokenStream, item: TokenStream) -> TokenStream {
 pub fn some_derive(_item: TokenStream) -> TokenStream {
     TokenStream::new()
 }
+
+/// Doc comment from the original crate
+#[proc_macro]
+pub fn reexported_macro(_input: TokenStream) -> TokenStream {
+    TokenStream::new()
+}
diff --git a/src/test/rustdoc/inline_cross/proc_macro.rs b/src/test/rustdoc/inline_cross/proc_macro.rs
index e1cdcf49402..6880e303df9 100644
--- a/src/test/rustdoc/inline_cross/proc_macro.rs
+++ b/src/test/rustdoc/inline_cross/proc_macro.rs
@@ -1,16 +1,17 @@
 // aux-build:proc_macro.rs
 // build-aux-docs
 
-// FIXME: if/when proc-macros start exporting their doc attributes across crates, we can turn on
-// cross-crate inlining for them
-
 extern crate some_macros;
 
 // @has proc_macro/index.html
-// @has - '//a/@href' '../some_macros/macro.some_proc_macro.html'
-// @has - '//a/@href' '../some_macros/attr.some_proc_attr.html'
-// @has - '//a/@href' '../some_macros/derive.SomeDerive.html'
-// @!has proc_macro/macro.some_proc_macro.html
-// @!has proc_macro/attr.some_proc_attr.html
-// @!has proc_macro/derive.SomeDerive.html
+// @has - '//a/@href' 'macro.some_proc_macro.html'
+// @has - '//a/@href' 'attr.some_proc_attr.html'
+// @has - '//a/@href' 'derive.SomeDerive.html'
+// @has proc_macro/macro.some_proc_macro.html
+// @has proc_macro/attr.some_proc_attr.html
+// @has proc_macro/derive.SomeDerive.html
 pub use some_macros::{some_proc_macro, some_proc_attr, SomeDerive};
+
+// @has proc_macro/macro.reexported_macro.html
+// @has - 'Doc comment from the original crate'
+pub use some_macros::reexported_macro;
diff --git a/src/test/rustdoc/proc-macro.rs b/src/test/rustdoc/proc-macro.rs
index 4bd0b092b55..82196e413e9 100644
--- a/src/test/rustdoc/proc-macro.rs
+++ b/src/test/rustdoc/proc-macro.rs
@@ -1,5 +1,6 @@
 // force-host
 // no-prefer-dynamic
+// compile-flags: --crate-type proc-macro --document-private-items
 
 #![crate_type="proc-macro"]
 #![crate_name="some_macros"]
@@ -58,7 +59,7 @@ pub fn some_derive(_item: TokenStream) -> TokenStream {
 }
 
 // @has some_macros/foo/index.html
-pub mod foo {
+mod foo {
     // @has - '//code' 'pub use some_proc_macro;'
     // @has - '//a/@href' '../../some_macros/macro.some_proc_macro.html'
     pub use some_proc_macro;
diff --git a/src/test/rustdoc/rustc-macro-crate.rs b/src/test/rustdoc/rustc-macro-crate.rs
index 2f6308b20c2..dd5edc984da 100644
--- a/src/test/rustdoc/rustc-macro-crate.rs
+++ b/src/test/rustdoc/rustc-macro-crate.rs
@@ -1,5 +1,6 @@
 // force-host
 // no-prefer-dynamic
+// compile-flags: --crate-type proc-macro
 
 #![crate_type = "proc-macro"]