Auto merge of rust-lang#111780 - weiznich:diagnostic_namespace, r=petrochenkov

Diagnostic namespace

This PR implements the basic infrastructure for accepting the `#[diagnostic]` attribute tool namespace as specified in rust-lang/rfcs#3368. Note: This RFC is not merged yet, but it seems like it will be accepted soon. I open this PR early on to get feedback on the actual implementation as soon as possible. This hopefully enables getting at least the diagnostic namespace to stable rust "soon", so that crates do not need to bump their MSRV if we stabilize actual attributes in this namespace.

 This PR only adds infrastructure accept attributes from this namespace, it does not add any specific attribute. Therefore the compiler will emit a lint warning for each attribute that's actually used. This namespace is added behind a feature flag, so it will be only available on a nightly compiler for now.

cc `@estebank` as they've supported me in planing, specifying and implementing this feature.

Author: bors

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -218,6 +218,19 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 }
             }
         }
+        if !attr.is_doc_comment()
+            && attr.get_normal_item().path.segments.len() == 2
+            && attr.get_normal_item().path.segments[0].ident.name == sym::diagnostic
+            && !self.features.diagnostic_namespace
+        {
+            let msg = "`#[diagnostic]` attribute name space is experimental";
+            gate_feature_post!(
+                self,
+                diagnostic_namespace,
+                attr.get_normal_item().path.segments[0].ident.span,
+                msg
+            );
+        }
 
         // Emit errors for non-staged-api crates.
         if !self.features.staged_api {

compiler/rustc_feature/src/active.rs

@@ -379,6 +379,8 @@ declare_features! (
     (active, deprecated_safe, "1.61.0", Some(94978), None),
     /// Allows having using `suggestion` in the `#[deprecated]` attribute.
     (active, deprecated_suggestion, "1.61.0", Some(94785), None),
+    /// Allows using the `#[diagnostic]` attribute tool namespace
+    (active, diagnostic_namespace, "CURRENT_RUSTC_VERSION", Some(94785), None),
     /// Controls errors in trait implementations.
     (active, do_not_recommend, "1.67.0", Some(51992), None),
     /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.

compiler/rustc_lint_defs/src/builtin.rs

@@ -3400,6 +3400,7 @@ declare_lint_pass! {
         UNFULFILLED_LINT_EXPECTATIONS,
         UNINHABITED_STATIC,
         UNKNOWN_CRATE_TYPES,
+        UNKNOWN_DIAGNOSTIC_ATTRIBUTES,
         UNKNOWN_LINTS,
         UNNAMEABLE_TYPES,
         UNREACHABLE_CODE,
@@ -4380,3 +4381,27 @@ declare_lint! {
     "effective visibility of a type is larger than the area in which it can be named",
     @feature_gate = sym::type_privacy_lints;
 }
+
+declare_lint! {
+    /// The `unknown_diagnostic_attributes` lint detects unrecognized diagnostic attributes.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// #![feature(diagnostic_namespace)]
+    /// #[diagnostic::does_not_exist]
+    /// struct Foo;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// It is usually a mistake to specify a diagnostic attribute that does not exist. Check
+    /// the spelling, and check the diagnostic attribute listing for the correct name. Also
+    /// consider if you are using an old version of the compiler, and the attribute
+    /// is only available in a newer version.
+    pub UNKNOWN_DIAGNOSTIC_ATTRIBUTES,
+    Warn,
+    "unrecognized diagnostic attribute"
+}

compiler/rustc_resolve/src/macros.rs

@@ -24,7 +24,9 @@ use rustc_hir::def_id::{CrateNum, LocalDefId};
 use rustc_middle::middle::stability;
 use rustc_middle::ty::RegisteredTools;
 use rustc_middle::ty::TyCtxt;
-use rustc_session::lint::builtin::{LEGACY_DERIVE_HELPERS, SOFT_UNSTABLE};
+use rustc_session::lint::builtin::{
+    LEGACY_DERIVE_HELPERS, SOFT_UNSTABLE, UNKNOWN_DIAGNOSTIC_ATTRIBUTES,
+};
 use rustc_session::lint::builtin::{UNUSED_MACROS, UNUSED_MACRO_RULES};
 use rustc_session::lint::BuiltinLintDiagnostics;
 use rustc_session::parse::feature_err;
@@ -140,9 +142,9 @@ pub(crate) fn registered_tools(tcx: TyCtxt<'_>, (): ()) -> RegisteredTools {
             }
         }
     }
-    // We implicitly add `rustfmt` and `clippy` to known tools,
+    // We implicitly add `rustfmt`, `clippy`, `diagnostic` to known tools,
     // but it's not an error to register them explicitly.
-    let predefined_tools = [sym::clippy, sym::rustfmt];
+    let predefined_tools = [sym::clippy, sym::rustfmt, sym::diagnostic];
     registered_tools.extend(predefined_tools.iter().cloned().map(Ident::with_dummy_span));
     registered_tools
 }
@@ -595,6 +597,18 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             }
         }
 
+        if res == Res::NonMacroAttr(NonMacroAttrKind::Tool)
+            && path.segments.len() >= 2
+            && path.segments[0].ident.name == sym::diagnostic
+        {
+            self.tcx.sess.parse_sess.buffer_lint(
+                UNKNOWN_DIAGNOSTIC_ATTRIBUTES,
+                path.segments[1].span(),
+                node_id,
+                "unknown diagnostic attribute",
+            );
+        }
+
         Ok((ext, res))
     }
 

compiler/rustc_span/src/symbol.rs

@@ -620,6 +620,7 @@ symbols! {
         destruct,
         destructuring_assignment,
         diagnostic,
+        diagnostic_namespace,
         direct,
         discriminant_kind,
         discriminant_type,

src/tools/tidy/src/ui_tests.rs

@@ -11,7 +11,7 @@ use std::path::{Path, PathBuf};
 const ENTRY_LIMIT: usize = 900;
 // FIXME: The following limits should be reduced eventually.
 const ISSUES_ENTRY_LIMIT: usize = 1893;
-const ROOT_ENTRY_LIMIT: usize = 870;
+const ROOT_ENTRY_LIMIT: usize = 871;
 
 const EXPECTED_TEST_FILE_EXTENSIONS: &[&str] = &[
     "rs",     // test source files

tests/ui/diagnostic_namespace/auxiliary/proc-macro-helper.rs

@@ -0,0 +1,12 @@
+// force-host
+// no-prefer-dynamic
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+
+#[proc_macro_attribute]
+pub fn diagnostic(i: TokenStream, _: TokenStream) -> TokenStream {
+    i
+}

tests/ui/diagnostic_namespace/can_use_the_diagnostic_name_in_other_places.rs

@@ -0,0 +1,13 @@
+// check-pass
+
+mod diagnostic {}
+
+macro_rules! diagnostic{
+    () => {}
+}
+
+#[allow(non_upper_case_globals)]
+const diagnostic: () = ();
+
+fn main() {
+}

tests/ui/diagnostic_namespace/existing_proc_macros.rs

@@ -0,0 +1,24 @@
+#![feature(diagnostic_namespace)]
+// check-pass
+// aux-build:proc-macro-helper.rs
+
+extern crate proc_macro_helper;
+
+mod test1 {
+    use proc_macro_helper::diagnostic;
+
+    #[diagnostic]
+    struct Foo;
+
+}
+
+mod test2 {
+    mod diagnostic {
+        pub use proc_macro_helper::diagnostic as on_unimplemented;
+    }
+
+    #[diagnostic::on_unimplemented]
+    trait Foo {}
+}
+
+fn main() {}

tests/ui/diagnostic_namespace/feature-gate-diagnostic_namespace.rs

@@ -0,0 +1,13 @@
+#[diagnostic::non_existing_attribute]
+//~^ERROR `#[diagnostic]` attribute name space is experimental [E0658]
+//~|WARNING unknown diagnostic attribute [unknown_diagnostic_attributes]
+pub trait Bar {
+}
+
+#[diagnostic::non_existing_attribute(with_option = "foo")]
+//~^ERROR `#[diagnostic]` attribute name space is experimental [E0658]
+//~|WARNING unknown diagnostic attribute [unknown_diagnostic_attributes]
+struct Foo;
+
+fn main() {
+}