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Never regard macro rules with compile_error! invocations as unused #97903

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Jun 11, 2022
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1 change: 1 addition & 0 deletions compiler/rustc_expand/src/lib.rs
Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
#![allow(rustc::potential_query_instability)]
#![feature(array_windows)]
#![feature(associated_type_bounds)]
#![feature(associated_type_defaults)]
#![feature(if_let_guard)]
Expand Down
46 changes: 40 additions & 6 deletions compiler/rustc_expand/src/mbe/macro_rules.rs
Original file line number Diff line number Diff line change
Expand Up @@ -380,7 +380,7 @@ pub fn compile_declarative_macro(
features: &Features,
def: &ast::Item,
edition: Edition,
) -> (SyntaxExtension, Vec<Span>) {
) -> (SyntaxExtension, Vec<(usize, Span)>) {
debug!("compile_declarative_macro: {:?}", def);
let mk_syn_ext = |expander| {
SyntaxExtension::new(
Expand Down Expand Up @@ -539,11 +539,22 @@ pub fn compile_declarative_macro(
None => {}
}

// Compute the spans of the macro rules
// We only take the span of the lhs here,
// so that the spans of created warnings are smaller.
let rule_spans = if def.id != DUMMY_NODE_ID {
lhses.iter().map(|lhs| lhs.span()).collect::<Vec<_>>()
// Compute the spans of the macro rules for unused rule linting.
// To avoid warning noise, only consider the rules of this
// macro for the lint, if all rules are valid.
// Also, we are only interested in non-foreign macros.
let rule_spans = if valid && def.id != DUMMY_NODE_ID {
lhses
.iter()
.zip(rhses.iter())
.enumerate()
// If the rhs contains an invocation like compile_error!,
// don't consider the rule for the unused rule lint.
.filter(|(_idx, (_lhs, rhs))| !has_compile_error_macro(rhs))
// We only take the span of the lhs here,
// so that the spans of created warnings are smaller.
.map(|(idx, (lhs, _rhs))| (idx, lhs.span()))
.collect::<Vec<_>>()
} else {
Vec::new()
};
Expand Down Expand Up @@ -651,6 +662,29 @@ fn check_matcher(sess: &ParseSess, def: &ast::Item, matcher: &[mbe::TokenTree])
err == sess.span_diagnostic.err_count()
}

fn has_compile_error_macro(rhs: &mbe::TokenTree) -> bool {
match rhs {
mbe::TokenTree::Delimited(_sp, d) => {
let has_compile_error = d.tts.array_windows::<3>().any(|[ident, bang, args]| {
if let mbe::TokenTree::Token(ident) = ident &&
let TokenKind::Ident(ident, _) = ident.kind &&
ident == sym::compile_error &&
let mbe::TokenTree::Token(bang) = bang &&
let TokenKind::Not = bang.kind &&
let mbe::TokenTree::Delimited(_, del) = args &&
del.delim != Delimiter::Invisible
{
true
} else {
false
}
});
if has_compile_error { true } else { d.tts.iter().any(has_compile_error_macro) }
}
_ => false,
}
}

// `The FirstSets` for a matcher is a mapping from subsequences in the
// matcher to the FIRST set for that subsequence.
//
Expand Down
6 changes: 3 additions & 3 deletions compiler/rustc_resolve/src/build_reduced_graph.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1220,12 +1220,12 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
ident: Ident,
def_id: LocalDefId,
node_id: NodeId,
rule_spans: &[Span],
rule_spans: &[(usize, Span)],
) {
if !ident.as_str().starts_with('_') {
self.r.unused_macros.insert(def_id, (node_id, ident));
for (rule_i, rule_span) in rule_spans.iter().enumerate() {
self.r.unused_macro_rules.insert((def_id, rule_i), (ident, *rule_span));
for (rule_i, rule_span) in rule_spans.iter() {
self.r.unused_macro_rules.insert((def_id, *rule_i), (ident, *rule_span));
}
}
}
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_resolve/src/macros.rs
Original file line number Diff line number Diff line change
Expand Up @@ -870,7 +870,7 @@ impl<'a> Resolver<'a> {
&mut self,
item: &ast::Item,
edition: Edition,
) -> (SyntaxExtension, Vec<Span>) {
) -> (SyntaxExtension, Vec<(usize, Span)>) {
let (mut result, mut rule_spans) = compile_declarative_macro(
&self.session,
self.session.features_untracked(),
Expand Down
27 changes: 27 additions & 0 deletions src/test/ui/lint/unused/unused-macro-rules-compile-error.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,27 @@
#![deny(unused_macro_rules)]
// To make sure we are not hitting this
#![deny(unused_macros)]

macro_rules! num {
(one) => { 1 };
// Most simple (and common) case
(two) => { compile_error!("foo"); };
// Some nested use
(two_) => { foo(compile_error!("foo")); };
(three) => { 3 };
(four) => { 4 }; //~ ERROR: rule of macro
}
const _NUM: u8 = num!(one) + num!(three);

// compile_error not used as a macro invocation
macro_rules! num2 {
(one) => { 1 };
// Only identifier present
(two) => { fn compile_error() {} }; //~ ERROR: rule of macro
// Only identifier and bang present
(two_) => { compile_error! }; //~ ERROR: rule of macro
(three) => { 3 };
}
const _NUM2: u8 = num2!(one) + num2!(three);

fn main() {}
26 changes: 26 additions & 0 deletions src/test/ui/lint/unused/unused-macro-rules-compile-error.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,26 @@
error: 5th rule of macro `num` is never used
--> $DIR/unused-macro-rules-compile-error.rs:12:5
|
LL | (four) => { 4 };
| ^^^^^^
|
note: the lint level is defined here
--> $DIR/unused-macro-rules-compile-error.rs:1:9
|
LL | #![deny(unused_macro_rules)]
| ^^^^^^^^^^^^^^^^^^

error: 3rd rule of macro `num2` is never used
--> $DIR/unused-macro-rules-compile-error.rs:22:5
|
LL | (two_) => { compile_error! };
| ^^^^^^

error: 2nd rule of macro `num2` is never used
--> $DIR/unused-macro-rules-compile-error.rs:20:5
|
LL | (two) => { fn compile_error() {} };
| ^^^^^

error: aborting due to 3 previous errors

11 changes: 11 additions & 0 deletions src/test/ui/lint/unused/unused-macro-rules-malformed-rule.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
#![deny(unused_macro_rules)]

macro_rules! foo {
(v) => {};
(w) => {};
() => 0; //~ ERROR: macro rhs must be delimited
}

fn main() {
foo!(v);
}
Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
error: macro rhs must be delimited
--> $DIR/unused-macro-rules-malformed-rule.rs:6:11
|
LL | () => 0;
| ^

error: aborting due to previous error

15 changes: 15 additions & 0 deletions src/test/ui/lint/unused/unused-macros-malformed-rule.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
#![deny(unused_macros)]

macro_rules! foo { //~ ERROR: unused macro definition
(v) => {};
() => 0; //~ ERROR: macro rhs must be delimited
}

macro_rules! bar {
(v) => {};
() => 0; //~ ERROR: macro rhs must be delimited
}

fn main() {
bar!(v);
}
26 changes: 26 additions & 0 deletions src/test/ui/lint/unused/unused-macros-malformed-rule.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,26 @@
error: macro rhs must be delimited
--> $DIR/unused-macros-malformed-rule.rs:5:11
|
LL | () => 0;
| ^

error: macro rhs must be delimited
--> $DIR/unused-macros-malformed-rule.rs:10:11
|
LL | () => 0;
| ^

error: unused macro definition: `foo`
--> $DIR/unused-macros-malformed-rule.rs:3:14
|
LL | macro_rules! foo {
| ^^^
|
note: the lint level is defined here
--> $DIR/unused-macros-malformed-rule.rs:1:9
|
LL | #![deny(unused_macros)]
| ^^^^^^^^^^^^^

error: aborting due to 3 previous errors