Rollup merge of #145153 - joshtriplett:macro-kinds-plural, r=petrochenkov

Handle macros with multiple kinds, and improve errors

(I recommend reviewing this commit-by-commit.)

Switch to a bitflags `MacroKinds` to support macros with more than one kind

Review everything that uses `MacroKind`, and switch anything that could refer to more than one kind to use `MacroKinds`.

Add a new `SyntaxExtensionKind::MacroRules` for `macro_rules!` macros, using the concrete `MacroRulesMacroExpander` type, and have it track which kinds it can handle. Eliminate the separate optional `attr_ext`, now that a `SyntaxExtension` can handle multiple macro kinds.

This also avoids the need to downcast when calling methods on `MacroRulesMacroExpander`, such as `get_unused_rule`.

Integrate macro kind checking into name resolution's `sub_namespace_match`, so that we only find a macro if it's the right type, and eliminate the special-case hack for attributes.

This allows detecting and report macro kind mismatches early, and more precisely, improving various error messages. In particular, this eliminates the case in `failed_to_match_macro` to check for a function-like invocation of a macro with no function-like rules.

Instead, macro kind mismatches now result in an unresolved macro, and we detect this case in `unresolved_macro_suggestions`, which now carefully distinguishes between a kind mismatch and other errors.

This also handles cases of forward-referenced attributes and cyclic attributes.

----

In this PR, I've minimally fixed up `rustdoc` so that it compiles and passes tests. This is just the minimal necessary fixes to handle the switch to `MacroKinds`, and it only works for macros that don't actually have multiple kinds. This will panic (with a `todo!`) if it encounters a macro with multiple kinds.

rustdoc needs further fixes to handle macros with multiple kinds, and to handle attributes and derive macros that aren't proc macros. I'd appreciate some help from a rustdoc expert on that.

----

r? ````````@petrochenkov````````

1 files changed, 38 insertions, 1 deletions

diff --git a/tests/ui/macros/macro-rules-attr-error.rs b/tests/ui/macros/macro-rules-attr-error.rs
index 1c8bb251e20..81eadb6692f 100644
--- a/tests/ui/macros/macro-rules-attr-error.rs
+++ b/tests/ui/macros/macro-rules-attr-error.rs
@@ -7,9 +7,46 @@ macro_rules! local_attr {
     //~^^ ERROR: local_attr
 }
 
+//~v NOTE: `fn_only` exists, but has no `attr` rules
+macro_rules! fn_only {
+    {} => {}
+}
+
+//~v NOTE: `attr_only` exists, but has no rules for function-like invocation
+macro_rules! attr_only {
+    attr() {} => {}
+}
+
 fn main() {
+    //~v NOTE: in this expansion of #[local_attr]
     #[local_attr]
     struct S;
 
-    local_attr!(arg); //~ ERROR: macro has no rules for function-like invocation
+    //~vv ERROR: cannot find macro `local_attr` in this scope
+    //~| NOTE: `local_attr` is in scope, but it is an attribute
+    local_attr!(arg);
+
+    //~v ERROR: cannot find attribute `fn_only` in this scope
+    #[fn_only]
+    struct S;
+
+    attr_only!(); //~ ERROR: cannot find macro `attr_only` in this scope
+}
+
+//~vv ERROR: cannot find attribute `forward_referenced_attr` in this scope
+//~| NOTE: consider moving the definition of `forward_referenced_attr` before this call
+#[forward_referenced_attr]
+struct S;
+
+//~v NOTE: a macro with the same name exists, but it appears later
+macro_rules! forward_referenced_attr {
+    attr() {} => {}
+}
+
+//~vv ERROR: cannot find attribute `cyclic_attr` in this scope
+//~| NOTE: consider moving the definition of `cyclic_attr` before this call
+#[cyclic_attr]
+//~v NOTE: a macro with the same name exists, but it appears later
+macro_rules! cyclic_attr {
+    attr() {} => {}
 }