Lint on function pointers used in patterns
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3795886f7e
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@ -351,10 +351,27 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
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ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::FnDef(..) => {
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PatKind::Constant { value: cv }
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}
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ty::RawPtr(pointee) if pointee.ty.is_sized(tcx.at(span), param_env) => {
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PatKind::Constant { value: cv }
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}
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// FIXME: these can have very suprising behaviour where optimization levels or other
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// compilation choices change the runtime behaviour of the match.
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// See https://github.com/rust-lang/rust/issues/70861 for examples.
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ty::FnPtr(..) | ty::RawPtr(..) => PatKind::Constant { value: cv },
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ty::FnPtr(..) | ty::RawPtr(..) => {
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if self.include_lint_checks && !self.saw_const_match_error.get() {
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self.saw_const_match_error.set(true);
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let msg = "function pointers and unsized pointers in patterns do not behave \
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deterministically. \
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See https://github.com/rust-lang/rust/issues/70861 for details.";
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tcx.struct_span_lint_hir(
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lint::builtin::POINTER_STRUCTURAL_MATCH,
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id,
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span,
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|lint| lint.build(&msg).emit(),
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);
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}
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PatKind::Constant { value: cv }
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}
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_ => {
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tcx.sess.delay_span_bug(span, &format!("cannot make a pattern out of {}", cv.ty));
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PatKind::Wild
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@ -2197,6 +2197,32 @@ declare_lint! {
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report_in_external_macro
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}
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declare_lint! {
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/// The `pointer_structural_match` lint detects pointers used in patterns that do not
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/// behave deterministically across optimizations.
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///
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/// ### Example
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///
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/// ```rust,compile_fail
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/// #![deny(pointer_structural_match)]
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/// fn foo(a: usize, b: usize) -> usize { a + b }
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/// const FOO: fn(usize, usize) -> usize = foo;
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/// fn main() {
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/// match FOO {
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/// FOO => {},
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/// _ => {},
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/// }
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/// }
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/// ```
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pub POINTER_STRUCTURAL_MATCH,
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Allow,
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"pointers are not structural-match",
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@future_incompatible = FutureIncompatibleInfo {
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reference: "issue #62411 <https://github.com/rust-lang/rust/issues/70861>",
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edition: None,
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};
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}
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declare_lint! {
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/// The `ambiguous_associated_items` lint detects ambiguity between
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/// [associated items] and [enum variants].
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@ -2630,6 +2656,7 @@ declare_lint_pass! {
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AMBIGUOUS_ASSOCIATED_ITEMS,
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MUTABLE_BORROW_RESERVATION_CONFLICT,
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INDIRECT_STRUCTURAL_MATCH,
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POINTER_STRUCTURAL_MATCH,
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SOFT_UNSTABLE,
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INLINE_NO_SANITIZE,
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ASM_SUB_REGISTER,
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@ -1,4 +1,7 @@
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// run-pass
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#![warn(pointer_structural_match)]
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type Func = fn(usize, usize) -> usize;
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fn foo(a: usize, b: usize) -> usize { a + b }
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@ -13,8 +16,10 @@ const BAR: Func = bar;
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fn main() {
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match test(std::env::consts::ARCH.len()) {
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FOO => println!("foo"),
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BAR => println!("bar"),
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FOO => println!("foo"), //~ WARN pointers in patterns do not behave deterministically
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//~^ WARN will become a hard error
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BAR => println!("bar"), //~ WARN pointers in patterns do not behave deterministically
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//~^ WARN will become a hard error
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_ => unreachable!(),
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}
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}
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25
src/test/ui/issues/issue-44333.stderr
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25
src/test/ui/issues/issue-44333.stderr
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@ -0,0 +1,25 @@
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warning: function pointers and unsized pointers in patterns do not behave deterministically. See https://github.com/rust-lang/rust/issues/70861 for details.
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--> $DIR/issue-44333.rs:19:9
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LL | FOO => println!("foo"),
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| ^^^
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note: the lint level is defined here
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--> $DIR/issue-44333.rs:3:9
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LL | #![warn(pointer_structural_match)]
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
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= note: for more information, see issue #62411 <https://github.com/rust-lang/rust/issues/70861>
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warning: function pointers and unsized pointers in patterns do not behave deterministically. See https://github.com/rust-lang/rust/issues/70861 for details.
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--> $DIR/issue-44333.rs:21:9
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LL | BAR => println!("bar"),
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| ^^^
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= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
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= note: for more information, see issue #62411 <https://github.com/rust-lang/rust/issues/70861>
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warning: 2 warnings emitted
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@ -5,6 +5,8 @@
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// cover the case this hit; I've since expanded it accordingly, but the
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// experience left me wary of leaving this regression test out.)
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#![warn(pointer_structural_match)]
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#[derive(Eq)]
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struct A {
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a: i64
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@ -31,6 +33,8 @@ fn main() {
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let s = B(my_fn);
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match s {
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B(TEST) => println!("matched"),
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//~^ WARN pointers in patterns do not behave deterministically
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//~| WARN this was previously accepted by the compiler but is being phased out
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_ => panic!("didn't match")
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};
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}
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16
src/test/ui/rfc1445/issue-63479-match-fnptr.stderr
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16
src/test/ui/rfc1445/issue-63479-match-fnptr.stderr
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@ -0,0 +1,16 @@
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warning: function pointers and unsized pointers in patterns do not behave deterministically. See https://github.com/rust-lang/rust/issues/70861 for details.
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--> $DIR/issue-63479-match-fnptr.rs:35:7
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LL | B(TEST) => println!("matched"),
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| ^^^^
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note: the lint level is defined here
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--> $DIR/issue-63479-match-fnptr.rs:8:9
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LL | #![warn(pointer_structural_match)]
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
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= note: for more information, see issue #62411 <https://github.com/rust-lang/rust/issues/70861>
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warning: 1 warning emitted
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