also lint against fn ptr and raw ptr nested inside the const

Author: RalfJung

compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs

@@ -239,19 +239,15 @@ impl<'tcx> ConstToPat<'tcx> {
                     }
                 }
             } else if !self.saw_const_match_lint.get() {
-                match cv.ty().kind() {
-                    ty::RawPtr(..) if have_valtree => {
-                        // This is a good raw pointer, it was accepted by valtree construction.
-                    }
-                    ty::FnPtr(..) | ty::RawPtr(..) => {
-                        self.tcx().emit_spanned_lint(
-                            lint::builtin::POINTER_STRUCTURAL_MATCH,
-                            self.id,
-                            self.span,
-                            PointerPattern,
-                        );
-                    }
-                    _ => {}
+                if !have_valtree {
+                    // The only way valtree construction can fail without the structural match
+                    // checker finding a violation is if there is a pointer somewhere.
+                    self.tcx().emit_spanned_lint(
+                        lint::builtin::POINTER_STRUCTURAL_MATCH,
+                        self.id,
+                        self.span,
+                        PointerPattern,
+                    );
                 }
             }
 

tests/ui/consts/const_in_pattern/issue-34784-match-on-non-int-raw-ptr.rs

@@ -1,6 +1,9 @@
 #![deny(pointer_structural_match)]
 #![allow(dead_code)]
+
 const C: *const u8 = &0;
+// Make sure we also find pointers nested in other types.
+const C_INNER: (*const u8, u8) = (C, 0);
 
 fn foo(x: *const u8) {
     match x {
@@ -10,6 +13,14 @@ fn foo(x: *const u8) {
     }
 }
 
+fn foo2(x: *const u8) {
+    match (x, 1) {
+        C_INNER => {} //~ERROR: behave unpredictably
+        //~| previously accepted
+        _ => {}
+    }
+}
+
 const D: *const [u8; 4] = b"abcd";
 
 fn main() {

tests/ui/consts/const_in_pattern/issue-34784-match-on-non-int-raw-ptr.stderr

@@ -1,5 +1,5 @@
 error: function pointers and raw pointers not derived from integers in patterns behave unpredictably and should not be relied upon. See https://github.com/rust-lang/rust/issues/70861 for details.
-  --> $DIR/issue-34784-match-on-non-int-raw-ptr.rs:7:9
+  --> $DIR/issue-34784-match-on-non-int-raw-ptr.rs:10:9
    |
 LL |         C => {}
    |         ^
@@ -13,13 +13,22 @@ LL | #![deny(pointer_structural_match)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: function pointers and raw pointers not derived from integers in patterns behave unpredictably and should not be relied upon. See https://github.com/rust-lang/rust/issues/70861 for details.
-  --> $DIR/issue-34784-match-on-non-int-raw-ptr.rs:17:9
+  --> $DIR/issue-34784-match-on-non-int-raw-ptr.rs:18:9
+   |
+LL |         C_INNER => {}
+   |         ^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #62411 <https://github.com/rust-lang/rust/issues/70861>
+
+error: function pointers and raw pointers not derived from integers in patterns behave unpredictably and should not be relied upon. See https://github.com/rust-lang/rust/issues/70861 for details.
+  --> $DIR/issue-34784-match-on-non-int-raw-ptr.rs:28:9
    |
 LL |         D => {}
    |         ^
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #62411 <https://github.com/rust-lang/rust/issues/70861>
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 

tests/ui/rfcs/rfc-1445-restrict-constants-in-patterns/issue-63479-match-fnptr.rs

@@ -26,15 +26,22 @@ fn my_fn(_args: &[A]) {
 }
 
 const TEST: Fn = my_fn;
+const TEST2: (Fn, u8) = (TEST, 0);
 
 struct B(Fn);
 
 fn main() {
   let s = B(my_fn);
   match s {
     B(TEST) => println!("matched"),
-     //~^ WARN behave unpredictably
+    //~^ WARN behave unpredictably
     //~| WARN this was previously accepted by the compiler but is being phased out
     _ => panic!("didn't match")
   };
+  match (s.0, 0) {
+    TEST2 => println!("matched"),
+    //~^ WARN behave unpredictably
+    //~| WARN this was previously accepted by the compiler but is being phased out
+    _ => panic!("didn't match")
+  }
 }

tests/ui/rfcs/rfc-1445-restrict-constants-in-patterns/issue-63479-match-fnptr.stderr

@@ -1,5 +1,5 @@
 warning: function pointers and raw pointers not derived from integers in patterns behave unpredictably and should not be relied upon. See https://github.com/rust-lang/rust/issues/70861 for details.
-  --> $DIR/issue-63479-match-fnptr.rs:35:7
+  --> $DIR/issue-63479-match-fnptr.rs:36:7
    |
 LL |     B(TEST) => println!("matched"),
    |       ^^^^
@@ -12,5 +12,14 @@ note: the lint level is defined here
 LL | #![warn(pointer_structural_match)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^
 
-warning: 1 warning emitted
+warning: function pointers and raw pointers not derived from integers in patterns behave unpredictably and should not be relied upon. See https://github.com/rust-lang/rust/issues/70861 for details.
+  --> $DIR/issue-63479-match-fnptr.rs:42:5
+   |
+LL |     TEST2 => println!("matched"),
+   |     ^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #62411 <https://github.com/rust-lang/rust/issues/70861>
+
+warning: 2 warnings emitted