Rollup merge of #107291 - oli-obk:rustdoc_breaking_change, r=estebank

[breaking change] Remove a rustdoc back compat warning

This warning was introduced in https://github.com/rust-lang/rust/pull/62855 for users who use `rustdoc` directly on proc macro crates (instead of using `cargo doc`) without passing `--crate-type proc-macro` (which `cargo doc` passed automatically).

5 files changed, 32 insertions, 30 deletions

diff --git a/compiler/rustc_interface/locales/en-US.ftl b/compiler/rustc_interface/locales/en-US.ftl
index a7bc0e7af1f..da58492ccf2 100644
--- a/compiler/rustc_interface/locales/en-US.ftl
+++ b/compiler/rustc_interface/locales/en-US.ftl
@@ -11,10 +11,6 @@ interface_mixed_bin_crate =
 interface_mixed_proc_macro_crate =
     cannot mix `proc-macro` crate type with others
 
-interface_proc_macro_doc_without_arg =
-    Trying to document proc macro crate without passing '--crate-type proc-macro to rustdoc
-    .warn = The generated documentation may be incorrect
-
 interface_error_writing_dependencies =
     error writing dependencies to `{$path}`: {$error}
 
diff --git a/compiler/rustc_interface/src/errors.rs b/compiler/rustc_interface/src/errors.rs
index 29543fe2f93..0eedee25026 100644
--- a/compiler/rustc_interface/src/errors.rs
+++ b/compiler/rustc_interface/src/errors.rs
@@ -32,10 +32,6 @@ pub struct MixedBinCrate;
 pub struct MixedProcMacroCrate;
 
 #[derive(Diagnostic)]
-#[diag(interface_proc_macro_doc_without_arg)]
-pub struct ProcMacroDocWithoutArg;
-
-#[derive(Diagnostic)]
 #[diag(interface_error_writing_dependencies)]
 pub struct ErrorWritingDependencies<'a> {
     pub path: &'a Path,
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index aa59654099a..81c1d665ef0 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -287,28 +287,18 @@ fn configure_and_expand(mut krate: ast::Crate, resolver: &mut Resolver<'_, '_>)
         sess.emit_warning(errors::ProcMacroCratePanicAbort);
     }
 
-    // For backwards compatibility, we don't try to run proc macro injection
-    // if rustdoc is run on a proc macro crate without '--crate-type proc-macro' being
-    // specified. This should only affect users who manually invoke 'rustdoc', as
-    // 'cargo doc' will automatically pass the proper '--crate-type' flags.
-    // However, we do emit a warning, to let such users know that they should
-    // start passing '--crate-type proc-macro'
-    if has_proc_macro_decls && sess.opts.actually_rustdoc && !is_proc_macro_crate {
-        sess.emit_warning(errors::ProcMacroDocWithoutArg);
-    } else {
-        krate = sess.time("maybe_create_a_macro_crate", || {
-            let is_test_crate = sess.opts.test;
-            rustc_builtin_macros::proc_macro_harness::inject(
-                sess,
-                resolver,
-                krate,
-                is_proc_macro_crate,
-                has_proc_macro_decls,
-                is_test_crate,
-                sess.diagnostic(),
-            )
-        });
-    }
+    krate = sess.time("maybe_create_a_macro_crate", || {
+        let is_test_crate = sess.opts.test;
+        rustc_builtin_macros::proc_macro_harness::inject(
+            sess,
+            resolver,
+            krate,
+            is_proc_macro_crate,
+            has_proc_macro_decls,
+            is_test_crate,
+            sess.diagnostic(),
+        )
+    });
 
     // Done with macro expansion!
 
diff --git a/tests/rustdoc-ui/proc_macro_bug.rs b/tests/rustdoc-ui/proc_macro_bug.rs
new file mode 100644
index 00000000000..e384e4863ad
--- /dev/null
+++ b/tests/rustdoc-ui/proc_macro_bug.rs
@@ -0,0 +1,12 @@
+// regression test for failing to pass `--crate-type proc-macro` to rustdoc
+// when documenting a proc macro crate https://github.com/rust-lang/rust/pull/107291
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+
+#[proc_macro_derive(DeriveA)]
+//~^ ERROR the `#[proc_macro_derive]` attribute is only usable with crates of the `proc-macro` crate type
+pub fn a_derive(input: TokenStream) -> TokenStream {
+    input
+}
diff --git a/tests/rustdoc-ui/proc_macro_bug.stderr b/tests/rustdoc-ui/proc_macro_bug.stderr
new file mode 100644
index 00000000000..5b048097c49
--- /dev/null
+++ b/tests/rustdoc-ui/proc_macro_bug.stderr
@@ -0,0 +1,8 @@
+error: the `#[proc_macro_derive]` attribute is only usable with crates of the `proc-macro` crate type
+  --> $DIR/proc_macro_bug.rs:8:1
+   |
+LL | #[proc_macro_derive(DeriveA)]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+