`zero_ptr`: lint in `const` context as well (#15152)

The lint was extra restrictive, and didn't suggest using
`core::ptr::null` and `core::ptr::null_mut` in `const` contexts although
they have been const-stabilized since Rust 1.24.

changelog: [`zero_ptr`]: lint in `const` context as well

@rustbot label +I-false-negative +C-bug

3 files changed, 23 insertions, 1 deletions

diff --git a/tests/ui/zero_ptr.fixed b/tests/ui/zero_ptr.fixed
index f2375d57f3a..f9d9d2db176 100644
--- a/tests/ui/zero_ptr.fixed
+++ b/tests/ui/zero_ptr.fixed
@@ -16,3 +16,11 @@ fn main() {
     let z = 0;
     let _ = z as *const usize; // this is currently not caught
 }
+
+const fn in_const_context() {
+    #[clippy::msrv = "1.23"]
+    let _: *const usize = 0 as *const _;
+    #[clippy::msrv = "1.24"]
+    let _: *const usize = std::ptr::null();
+    //~^ zero_ptr
+}
diff --git a/tests/ui/zero_ptr.rs b/tests/ui/zero_ptr.rs
index ee01e426a43..41455fee5b5 100644
--- a/tests/ui/zero_ptr.rs
+++ b/tests/ui/zero_ptr.rs
@@ -16,3 +16,11 @@ fn main() {
     let z = 0;
     let _ = z as *const usize; // this is currently not caught
 }
+
+const fn in_const_context() {
+    #[clippy::msrv = "1.23"]
+    let _: *const usize = 0 as *const _;
+    #[clippy::msrv = "1.24"]
+    let _: *const usize = 0 as *const _;
+    //~^ zero_ptr
+}
diff --git a/tests/ui/zero_ptr.stderr b/tests/ui/zero_ptr.stderr
index 8dc781f3625..81269de6c60 100644
--- a/tests/ui/zero_ptr.stderr
+++ b/tests/ui/zero_ptr.stderr
@@ -31,5 +31,11 @@ error: `0 as *mut _` detected
 LL |     foo(0 as *const _, 0 as *mut _);
    |                        ^^^^^^^^^^^ help: try: `std::ptr::null_mut()`
 
-error: aborting due to 5 previous errors
+error: `0 as *const _` detected
+  --> tests/ui/zero_ptr.rs:24:27
+   |
+LL |     let _: *const usize = 0 as *const _;
+   |                           ^^^^^^^^^^^^^ help: try: `std::ptr::null()`
+
+error: aborting due to 6 previous errors