Handle macros with multiple kinds, and improve errors by joshtriplett · Pull Request #145153 · rust-lang/rust

@rustbot rustbot added S-waiting-on-review

Status: Awaiting review from the assignee but also interested parties.

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Aug 9, 2025

This was referenced

Aug 10, 2025

petrochenkov

petrochenkov

@rustbot rustbot added S-waiting-on-review

Status: Awaiting review from the assignee but also interested parties.

and removed S-waiting-on-author

Status: This is awaiting some action (such as code changes or more information) from the author.

labels

Aug 11, 2025

petrochenkov

jdonszelmann added a commit to jdonszelmann/rust that referenced this pull request

Aug 13, 2025
…=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`````

bors added a commit that referenced this pull request

Aug 13, 2025
Rollup of 9 pull requests

Successful merges:

 - #122661 (Change the desugaring of `assert!` for better error output)
 - #138736 (Sanitizers target modificators)
 - #144955 (search graph: lazily update parent goals)
 - #145120 (llvm: Accept new LLVM lifetime format)
 - #145153 (Handle macros with multiple kinds, and improve errors)
 - #145189 (Weekly `cargo update`)
 - #145250 (Add regression test for former ICE involving malformed meta items containing interpolated tokens)
 - #145309 (Fix `-Zregparm` for LLVM builtins)
 - #145331 (Make std use the edition 2024 prelude)

r? `@ghost`
`@rustbot` modify labels: rollup

GuillaumeGomez added a commit to GuillaumeGomez/rust that referenced this pull request

Aug 13, 2025
…=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``````

GuillaumeGomez added a commit to GuillaumeGomez/rust that referenced this pull request

Aug 13, 2025
…=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```````

This was referenced

Aug 13, 2025

bors added a commit that referenced this pull request

Aug 13, 2025
Rollup of 9 pull requests

Successful merges:

 - #144761 (aarch64: Make `outline-atomics` a known target feature)
 - #144949 (More `Printer` cleanups)
 - #144955 (search graph: lazily update parent goals)
 - #144962 (Add aarch64_be-unknown-none-softfloat target)
 - #145153 (Handle macros with multiple kinds, and improve errors)
 - #145241 ([AVR] Changed data_layout)
 - #145341 (Install libgccjit into the compiler's sysroot when cg_gcc is enabled)
 - #145349 (Correctly handle when there are no unstable items in the documented crate)
 - #145356 (Add another example for escaped `#` character in doctest in rustdoc book)

r? `@ghost`
`@rustbot` modify labels: rollup

rust-timer added a commit that referenced this pull request

Aug 13, 2025
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````````

jhpratt added a commit to jhpratt/rust that referenced this pull request

Aug 16, 2025
…enkov

Implement declarative (`macro_rules!`) derive macros (RFC 3698)

This is a draft for review, and should not be merged yet.

This is layered atop rust-lang#145153 , and has
only two additional commits atop that. The first handles parsing and provides a
test for various parse errors. The second implements expansion and handles
application.

This implements RFC 3698, "Declarative (`macro_rules!`) derive macros".
Tracking issue: rust-lang#143549

This has one remaining issue, which I could use some help debugging: in
`tests/ui/macros/macro-rules-derive-error.rs`, the diagnostics for
`derive(fn_only)` (for a `fn_only` with no `derive` rules) and
`derive(ForwardReferencedDerive)` both get emitted twice, as a duplicate
diagnostic.

From what I can tell via adding some debugging code,
`unresolved_macro_suggestions` is getting called twice from
`finalize_macro_resolutions` for each of them, because
`self.single_segment_macro_resolutions` has two entries for the macro, with two
different `parent_scope` values. I'm not clear on why that happened; it doesn't
happen with the equivalent code using attrs.

I'd welcome any suggestions for fixing this.

Zalathar added a commit to Zalathar/rust that referenced this pull request

Aug 16, 2025
…enkov

Implement declarative (`macro_rules!`) derive macros (RFC 3698)

This is a draft for review, and should not be merged yet.

This is layered atop rust-lang#145153 , and has
only two additional commits atop that. The first handles parsing and provides a
test for various parse errors. The second implements expansion and handles
application.

This implements RFC 3698, "Declarative (`macro_rules!`) derive macros".
Tracking issue: rust-lang#143549

This has one remaining issue, which I could use some help debugging: in
`tests/ui/macros/macro-rules-derive-error.rs`, the diagnostics for
`derive(fn_only)` (for a `fn_only` with no `derive` rules) and
`derive(ForwardReferencedDerive)` both get emitted twice, as a duplicate
diagnostic.

From what I can tell via adding some debugging code,
`unresolved_macro_suggestions` is getting called twice from
`finalize_macro_resolutions` for each of them, because
`self.single_segment_macro_resolutions` has two entries for the macro, with two
different `parent_scope` values. I'm not clear on why that happened; it doesn't
happen with the equivalent code using attrs.

I'd welcome any suggestions for fixing this.

Zalathar added a commit to Zalathar/rust that referenced this pull request

Aug 17, 2025
…enkov

Implement declarative (`macro_rules!`) derive macros (RFC 3698)

This is a draft for review, and should not be merged yet.

This is layered atop rust-lang#145153 , and has
only two additional commits atop that. The first handles parsing and provides a
test for various parse errors. The second implements expansion and handles
application.

This implements RFC 3698, "Declarative (`macro_rules!`) derive macros".
Tracking issue: rust-lang#143549

This has one remaining issue, which I could use some help debugging: in
`tests/ui/macros/macro-rules-derive-error.rs`, the diagnostics for
`derive(fn_only)` (for a `fn_only` with no `derive` rules) and
`derive(ForwardReferencedDerive)` both get emitted twice, as a duplicate
diagnostic.

From what I can tell via adding some debugging code,
`unresolved_macro_suggestions` is getting called twice from
`finalize_macro_resolutions` for each of them, because
`self.single_segment_macro_resolutions` has two entries for the macro, with two
different `parent_scope` values. I'm not clear on why that happened; it doesn't
happen with the equivalent code using attrs.

I'd welcome any suggestions for fixing this.

Zalathar added a commit to Zalathar/rust that referenced this pull request

Aug 17, 2025
…enkov

Implement declarative (`macro_rules!`) derive macros (RFC 3698)

This is a draft for review, and should not be merged yet.

This is layered atop rust-lang#145153 , and has
only two additional commits atop that. The first handles parsing and provides a
test for various parse errors. The second implements expansion and handles
application.

This implements RFC 3698, "Declarative (`macro_rules!`) derive macros".
Tracking issue: rust-lang#143549

This has one remaining issue, which I could use some help debugging: in
`tests/ui/macros/macro-rules-derive-error.rs`, the diagnostics for
`derive(fn_only)` (for a `fn_only` with no `derive` rules) and
`derive(ForwardReferencedDerive)` both get emitted twice, as a duplicate
diagnostic.

From what I can tell via adding some debugging code,
`unresolved_macro_suggestions` is getting called twice from
`finalize_macro_resolutions` for each of them, because
`self.single_segment_macro_resolutions` has two entries for the macro, with two
different `parent_scope` values. I'm not clear on why that happened; it doesn't
happen with the equivalent code using attrs.

I'd welcome any suggestions for fixing this.

Zalathar added a commit to Zalathar/rust that referenced this pull request

Aug 17, 2025
…enkov

Implement declarative (`macro_rules!`) derive macros (RFC 3698)

This is a draft for review, and should not be merged yet.

This is layered atop rust-lang#145153 , and has
only two additional commits atop that. The first handles parsing and provides a
test for various parse errors. The second implements expansion and handles
application.

This implements RFC 3698, "Declarative (`macro_rules!`) derive macros".
Tracking issue: rust-lang#143549

This has one remaining issue, which I could use some help debugging: in
`tests/ui/macros/macro-rules-derive-error.rs`, the diagnostics for
`derive(fn_only)` (for a `fn_only` with no `derive` rules) and
`derive(ForwardReferencedDerive)` both get emitted twice, as a duplicate
diagnostic.

From what I can tell via adding some debugging code,
`unresolved_macro_suggestions` is getting called twice from
`finalize_macro_resolutions` for each of them, because
`self.single_segment_macro_resolutions` has two entries for the macro, with two
different `parent_scope` values. I'm not clear on why that happened; it doesn't
happen with the equivalent code using attrs.

I'd welcome any suggestions for fixing this.

Zalathar added a commit to Zalathar/rust that referenced this pull request

Aug 17, 2025
…enkov

Implement declarative (`macro_rules!`) derive macros (RFC 3698)

This is a draft for review, and should not be merged yet.

This is layered atop rust-lang#145153 , and has
only two additional commits atop that. The first handles parsing and provides a
test for various parse errors. The second implements expansion and handles
application.

This implements RFC 3698, "Declarative (`macro_rules!`) derive macros".
Tracking issue: rust-lang#143549

This has one remaining issue, which I could use some help debugging: in
`tests/ui/macros/macro-rules-derive-error.rs`, the diagnostics for
`derive(fn_only)` (for a `fn_only` with no `derive` rules) and
`derive(ForwardReferencedDerive)` both get emitted twice, as a duplicate
diagnostic.

From what I can tell via adding some debugging code,
`unresolved_macro_suggestions` is getting called twice from
`finalize_macro_resolutions` for each of them, because
`self.single_segment_macro_resolutions` has two entries for the macro, with two
different `parent_scope` values. I'm not clear on why that happened; it doesn't
happen with the equivalent code using attrs.

I'd welcome any suggestions for fixing this.

Zalathar added a commit to Zalathar/rust that referenced this pull request

Aug 17, 2025
…enkov

Implement declarative (`macro_rules!`) derive macros (RFC 3698)

This is a draft for review, and should not be merged yet.

This is layered atop rust-lang#145153 , and has
only two additional commits atop that. The first handles parsing and provides a
test for various parse errors. The second implements expansion and handles
application.

This implements RFC 3698, "Declarative (`macro_rules!`) derive macros".
Tracking issue: rust-lang#143549

This has one remaining issue, which I could use some help debugging: in
`tests/ui/macros/macro-rules-derive-error.rs`, the diagnostics for
`derive(fn_only)` (for a `fn_only` with no `derive` rules) and
`derive(ForwardReferencedDerive)` both get emitted twice, as a duplicate
diagnostic.

From what I can tell via adding some debugging code,
`unresolved_macro_suggestions` is getting called twice from
`finalize_macro_resolutions` for each of them, because
`self.single_segment_macro_resolutions` has two entries for the macro, with two
different `parent_scope` values. I'm not clear on why that happened; it doesn't
happen with the equivalent code using attrs.

I'd welcome any suggestions for fixing this.

Zalathar added a commit to Zalathar/rust that referenced this pull request

Aug 18, 2025
…enkov

Implement declarative (`macro_rules!`) derive macros (RFC 3698)

This is a draft for review, and should not be merged yet.

This is layered atop rust-lang#145153 , and has
only two additional commits atop that. The first handles parsing and provides a
test for various parse errors. The second implements expansion and handles
application.

This implements RFC 3698, "Declarative (`macro_rules!`) derive macros".
Tracking issue: rust-lang#143549

This has one remaining issue, which I could use some help debugging: in
`tests/ui/macros/macro-rules-derive-error.rs`, the diagnostics for
`derive(fn_only)` (for a `fn_only` with no `derive` rules) and
`derive(ForwardReferencedDerive)` both get emitted twice, as a duplicate
diagnostic.

From what I can tell via adding some debugging code,
`unresolved_macro_suggestions` is getting called twice from
`finalize_macro_resolutions` for each of them, because
`self.single_segment_macro_resolutions` has two entries for the macro, with two
different `parent_scope` values. I'm not clear on why that happened; it doesn't
happen with the equivalent code using attrs.

I'd welcome any suggestions for fixing this.

rust-timer added a commit that referenced this pull request

Aug 18, 2025
Rollup merge of #145208 - joshtriplett:mbe-derive, r=petrochenkov

Implement declarative (`macro_rules!`) derive macros (RFC 3698)

This is a draft for review, and should not be merged yet.

This is layered atop #145153 , and has
only two additional commits atop that. The first handles parsing and provides a
test for various parse errors. The second implements expansion and handles
application.

This implements RFC 3698, "Declarative (`macro_rules!`) derive macros".
Tracking issue: #143549

This has one remaining issue, which I could use some help debugging: in
`tests/ui/macros/macro-rules-derive-error.rs`, the diagnostics for
`derive(fn_only)` (for a `fn_only` with no `derive` rules) and
`derive(ForwardReferencedDerive)` both get emitted twice, as a duplicate
diagnostic.

From what I can tell via adding some debugging code,
`unresolved_macro_suggestions` is getting called twice from
`finalize_macro_resolutions` for each of them, because
`self.single_segment_macro_resolutions` has two entries for the macro, with two
different `parent_scope` values. I'm not clear on why that happened; it doesn't
happen with the equivalent code using attrs.

I'd welcome any suggestions for fixing this.

flip1995 pushed a commit to flip1995/rust that referenced this pull request

Aug 22, 2025
…=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````````