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expand: Preserve order of inert attributes during expansion #82419

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Feb 27, 2021
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expand: Preserve order of inert attributes during expansion #82419

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c02d210
Add tests
petrochenkov Feb 22, 2021
fc9d578
expand: Preserve order of inert attributes during expansion
petrochenkov Feb 22, 2021
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23 changes: 14 additions & 9 deletions compiler/rustc_expand/src/expand.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -301,6 +301,8 @@ pub enum InvocationKind {
},
Attr {
attr: ast::Attribute,
// Re-insertion position for inert attributes.
pos: usize,
item: Annotatable,
// Required for resolving derive helper attributes.
derives: Vec<Path>,
Expand Down Expand Up @@ -690,7 +692,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
}
_ => unreachable!(),
},
InvocationKind::Attr { attr, mut item, derives } => match ext {
InvocationKind::Attr { attr, pos, mut item, derives } => match ext {
SyntaxExtensionKind::Attr(expander) => {
self.gate_proc_macro_input(&item);
self.gate_proc_macro_attr_item(span, &item);
Expand Down Expand Up @@ -721,7 +723,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
ExpandResult::Retry(item) => {
// Reassemble the original invocation for retrying.
return ExpandResult::Retry(Invocation {
kind: InvocationKind::Attr { attr, item, derives },
kind: InvocationKind::Attr { attr, pos, item, derives },
..invoc
});
}
Expand All @@ -739,7 +741,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
if *mark_used {
self.cx.sess.mark_attr_used(&attr);
}
item.visit_attrs(|attrs| attrs.push(attr));
item.visit_attrs(|attrs| attrs.insert(pos, attr));
fragment_kind.expect_from_annotatables(iter::once(item))
}
_ => unreachable!(),
Expand Down Expand Up @@ -1000,17 +1002,20 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {

fn collect_attr(
&mut self,
(attr, derives): (ast::Attribute, Vec<Path>),
(attr, pos, derives): (ast::Attribute, usize, Vec<Path>),
item: Annotatable,
kind: AstFragmentKind,
) -> AstFragment {
self.collect(kind, InvocationKind::Attr { attr, item, derives })
self.collect(kind, InvocationKind::Attr { attr, pos, item, derives })
}

/// If `item` is an attribute invocation, remove the attribute and return it together with
/// derives following it. We have to collect the derives in order to resolve legacy derive
/// helpers (helpers written before derives that introduce them).
fn take_first_attr(&mut self, item: &mut impl HasAttrs) -> Option<(ast::Attribute, Vec<Path>)> {
/// its position and derives following it. We have to collect the derives in order to resolve
/// legacy derive helpers (helpers written before derives that introduce them).
fn take_first_attr(
&mut self,
item: &mut impl HasAttrs,
) -> Option<(ast::Attribute, usize, Vec<Path>)> {
let mut attr = None;

item.visit_attrs(|attrs| {
Expand All @@ -1033,7 +1038,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
})
.collect();

(attr, following_derives)
(attr, attr_pos, following_derives)
})
});

Expand Down
22 changes: 16 additions & 6 deletions src/test/ui/proc-macro/auxiliary/test-macros.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@
#![crate_type = "proc-macro"]

extern crate proc_macro;
use proc_macro::TokenStream;
use proc_macro::{TokenStream, TokenTree};

// Macro that return empty token stream.

Expand Down Expand Up @@ -80,6 +80,10 @@ pub fn recollect_derive(input: TokenStream) -> TokenStream {
// Macros that print their input in the original and re-collected forms (if they differ).

fn print_helper(input: TokenStream, kind: &str) -> TokenStream {
print_helper_ext(input, kind, true)
}

fn print_helper_ext(input: TokenStream, kind: &str, debug: bool) -> TokenStream {
let input_display = format!("{}", input);
let input_debug = format!("{:#?}", input);
let recollected = input.into_iter().collect();
Expand All @@ -89,9 +93,11 @@ fn print_helper(input: TokenStream, kind: &str) -> TokenStream {
if recollected_display != input_display {
println!("PRINT-{} RE-COLLECTED (DISPLAY): {}", kind, recollected_display);
}
println!("PRINT-{} INPUT (DEBUG): {}", kind, input_debug);
if recollected_debug != input_debug {
println!("PRINT-{} RE-COLLECTED (DEBUG): {}", kind, recollected_debug);
if debug {
println!("PRINT-{} INPUT (DEBUG): {}", kind, input_debug);
if recollected_debug != input_debug {
println!("PRINT-{} RE-COLLECTED (DEBUG): {}", kind, recollected_debug);
}
}
recollected
}
Expand All @@ -108,8 +114,12 @@ pub fn print_bang_consume(input: TokenStream) -> TokenStream {
}

#[proc_macro_attribute]
pub fn print_attr(_: TokenStream, input: TokenStream) -> TokenStream {
print_helper(input, "ATTR")
pub fn print_attr(args: TokenStream, input: TokenStream) -> TokenStream {
let debug = match &args.into_iter().collect::<Vec<_>>()[..] {
[TokenTree::Ident(ident)] if ident.to_string() == "nodebug" => false,
_ => true,
};
print_helper_ext(input, "ATTR", debug)
}

#[proc_macro_attribute]
Expand Down
12 changes: 12 additions & 0 deletions src/test/ui/proc-macro/derive-helper-legacy-spurious.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
// aux-build:test-macros.rs

#![dummy] //~ ERROR cannot find attribute `dummy` in this scope

#[macro_use]
extern crate test_macros;

#[derive(Empty)] //~ ERROR cannot determine resolution for the attribute macro `derive`
#[empty_helper] //~ ERROR cannot find attribute `empty_helper` in this scope
struct Foo {}

fn main() {}
22 changes: 22 additions & 0 deletions src/test/ui/proc-macro/derive-helper-legacy-spurious.stderr
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Original file line number Diff line number Diff line change
@@ -0,0 +1,22 @@
error: cannot find attribute `dummy` in this scope
--> $DIR/derive-helper-legacy-spurious.rs:3:4
|
LL | #![dummy]
| ^^^^^

error: cannot determine resolution for the attribute macro `derive`
--> $DIR/derive-helper-legacy-spurious.rs:8:3
|
LL | #[derive(Empty)]
| ^^^^^^
|
= note: import resolution is stuck, try simplifying macro imports

error: cannot find attribute `empty_helper` in this scope
--> $DIR/derive-helper-legacy-spurious.rs:9:3
|
LL | #[empty_helper]
| ^^^^^^^^^^^^

error: aborting due to 3 previous errors

23 changes: 23 additions & 0 deletions src/test/ui/proc-macro/inert-attribute-order.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,23 @@
// Order of inert attributes, both built-in and custom is preserved during expansion.

// check-pass
// compile-flags: -Z span-debug
// aux-build:test-macros.rs

#![no_std] // Don't load unnecessary hygiene information from std
extern crate std;

#[macro_use]
extern crate test_macros;

/// 1
#[rustfmt::attr2]
#[doc = "3"]
#[print_attr(nodebug)]
#[doc = "4"]
#[rustfmt::attr5]
/// 6
#[print_attr(nodebug)]
struct S;

fn main() {}
7 changes: 7 additions & 0 deletions src/test/ui/proc-macro/inert-attribute-order.stdout
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Original file line number Diff line number Diff line change
@@ -0,0 +1,7 @@
PRINT-ATTR INPUT (DISPLAY): /// 1
#[rustfmt :: attr2] #[doc = "3"] #[doc = "4"] #[rustfmt :: attr5] /// 6
#[print_attr(nodebug)] struct S ;
PRINT-ATTR RE-COLLECTED (DISPLAY): #[doc = " 1"] #[rustfmt :: attr2] #[doc = "3"] #[doc = "4"]
#[rustfmt :: attr5] #[doc = " 6"] #[print_attr(nodebug)] struct S ;
PRINT-ATTR INPUT (DISPLAY): #[doc = " 1"] #[rustfmt :: attr2] #[doc = "3"] #[doc = "4"]
#[rustfmt :: attr5] #[doc = " 6"] struct S ;
64 changes: 32 additions & 32 deletions src/test/ui/proc-macro/issue-75930-derive-cfg.stdout
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@@ -1,4 +1,4 @@
PRINT-ATTR INPUT (DISPLAY): #[allow(dead_code)] #[derive(Print)] #[print_helper(b)] #[print_helper(a)]
PRINT-ATTR INPUT (DISPLAY): #[print_helper(a)] #[allow(dead_code)] #[derive(Print)] #[print_helper(b)]
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@Aaron1011 Aaron1011 Feb 23, 2021 •
edited
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This is a subtle detail that I just noticed - since we perform cfg-stripping before invoking custom attributes (e.g. #[my_attr] #[cfg(FALSE)] struct Foo {} does nothing), we also expand #[cfg_attr]. So, an attribute macro sees expanded #[cfg_attr] attributes (e.g. the #[allow(dead_code)]) at the 'top level' of the attribute target, but not anywhere else. For example, you can see #[cfg_attr(not(FALSE), allow(warnings))] in the input below.

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@petrochenkov petrochenkov Feb 23, 2021 •
edited
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since we perform cfg-stripping before invoking custom attributes

This is something I want to change, btw (and make the expansion order fully left-to-right).
It will certainly needs a crater run, but I think we'll be able to do this in practice, similarly to #79078.

struct Foo < #[cfg(FALSE)] A, B >
{
#[cfg(FALSE)] first : String, #[cfg_attr(FALSE, deny(warnings))] second :
Expand All @@ -23,6 +23,31 @@ struct Foo < #[cfg(FALSE)] A, B >
}], #[print_helper(d)] fourth : B
}
PRINT-ATTR INPUT (DEBUG): TokenStream [
Punct {
ch: '#',
spacing: Alone,
span: $DIR/issue-75930-derive-cfg.rs:16:1: 16:2 (#0),
},
Group {
delimiter: Bracket,
stream: TokenStream [
Ident {
ident: "print_helper",
span: $DIR/issue-75930-derive-cfg.rs:16:3: 16:15 (#0),
},
Group {
delimiter: Parenthesis,
stream: TokenStream [
Ident {
ident: "a",
span: $DIR/issue-75930-derive-cfg.rs:16:16: 16:17 (#0),
},
],
span: $DIR/issue-75930-derive-cfg.rs:16:15: 16:18 (#0),
},
],
span: $DIR/issue-75930-derive-cfg.rs:16:2: 16:19 (#0),
},
Punct {
ch: '#',
spacing: Alone,
Expand Down Expand Up @@ -98,31 +123,6 @@ PRINT-ATTR INPUT (DEBUG): TokenStream [
],
span: $DIR/issue-75930-derive-cfg.rs:21:2: 21:19 (#0),
},
Punct {
ch: '#',
spacing: Alone,
span: $DIR/issue-75930-derive-cfg.rs:16:1: 16:2 (#0),
},
Group {
delimiter: Bracket,
stream: TokenStream [
Ident {
ident: "print_helper",
span: $DIR/issue-75930-derive-cfg.rs:16:3: 16:15 (#0),
},
Group {
delimiter: Parenthesis,
stream: TokenStream [
Ident {
ident: "a",
span: $DIR/issue-75930-derive-cfg.rs:16:16: 16:17 (#0),
},
],
span: $DIR/issue-75930-derive-cfg.rs:16:15: 16:18 (#0),
},
],
span: $DIR/issue-75930-derive-cfg.rs:16:2: 16:19 (#0),
},
Ident {
ident: "struct",
span: $DIR/issue-75930-derive-cfg.rs:22:1: 22:7 (#0),
Expand Down Expand Up @@ -1194,7 +1194,7 @@ PRINT-ATTR INPUT (DEBUG): TokenStream [
span: $DIR/issue-75930-derive-cfg.rs:22:32: 65:2 (#0),
},
]
PRINT-DERIVE INPUT (DISPLAY): #[allow(dead_code)] #[print_helper(b)] #[print_helper(a)] struct Foo < B >
PRINT-DERIVE INPUT (DISPLAY): #[print_helper(a)] #[allow(dead_code)] #[print_helper(b)] struct Foo < B >
{
second : bool, third :
[u8 ;
Expand All @@ -1217,14 +1217,14 @@ PRINT-DERIVE INPUT (DEBUG): TokenStream [
delimiter: Bracket,
stream: TokenStream [
Ident {
ident: "allow",
ident: "print_helper",
span: $DIR/issue-75930-derive-cfg.rs:22:1: 65:2 (#0),
},
Group {
delimiter: Parenthesis,
stream: TokenStream [
Ident {
ident: "dead_code",
ident: "a",
span: $DIR/issue-75930-derive-cfg.rs:22:1: 65:2 (#0),
},
],
Expand All @@ -1242,14 +1242,14 @@ PRINT-DERIVE INPUT (DEBUG): TokenStream [
delimiter: Bracket,
stream: TokenStream [
Ident {
ident: "print_helper",
ident: "allow",
span: $DIR/issue-75930-derive-cfg.rs:22:1: 65:2 (#0),
},
Group {
delimiter: Parenthesis,
stream: TokenStream [
Ident {
ident: "b",
ident: "dead_code",
span: $DIR/issue-75930-derive-cfg.rs:22:1: 65:2 (#0),
},
],
Expand All @@ -1274,7 +1274,7 @@ PRINT-DERIVE INPUT (DEBUG): TokenStream [
delimiter: Parenthesis,
stream: TokenStream [
Ident {
ident: "a",
ident: "b",
span: $DIR/issue-75930-derive-cfg.rs:22:1: 65:2 (#0),
},
],
Expand Down