Add test for dereferencing raw pointers and immediately referencing again

Author: oli-obk

src/test/ui/consts/min_const_fn/min_const_fn_unsafe_feature_gate.rs

@@ -47,6 +47,9 @@ const unsafe fn foo10_2() -> *const Vec<std::cell::Cell<u32>> {
 const unsafe fn foo30_3(x: *mut usize) -> usize { *x } //~ ERROR not allowed in const fn
 //~^ dereferencing raw pointers in constant functions
 
+const unsafe fn foo30_4(x: *mut usize) -> &'static usize { &*x } //~ ERROR not allowed in const fn
+//~^ dereferencing raw pointers in constant functions
+
 fn main() {}
 
 const unsafe fn no_union() {

src/test/ui/consts/min_const_fn/min_const_fn_unsafe_feature_gate.stderr

@@ -6,8 +6,16 @@ LL | const unsafe fn foo30_3(x: *mut usize) -> usize { *x } //~ ERROR not allowe
    |
    = help: add #![feature(const_raw_ptr_deref)] to the crate attributes to enable
 
+error[E0658]: dereferencing raw pointers in constant functions is unstable (see issue #51911)
+  --> $DIR/min_const_fn_unsafe_feature_gate.rs:50:60
+   |
+LL | const unsafe fn foo30_4(x: *mut usize) -> &'static usize { &*x } //~ ERROR not allowed in const fn
+   |                                                            ^^^
+   |
+   = help: add #![feature(const_raw_ptr_deref)] to the crate attributes to enable
+
 error[E0658]: unions in const fn are unstable (see issue #51909)
-  --> $DIR/min_const_fn_unsafe_feature_gate.rs:54:5
+  --> $DIR/min_const_fn_unsafe_feature_gate.rs:57:5
    |
 LL |     Foo { x: () }.y //~ ERROR not allowed in const fn
    |     ^^^^^^^^^^^^^^^
@@ -46,14 +54,22 @@ LL | const unsafe fn foo30_3(x: *mut usize) -> usize { *x } //~ ERROR not allowe
    |
    = note: raw pointers may be NULL, dangling or unaligned; they can violate aliasing rules and cause data races: all of these are undefined behavior
 
+error: dereference of raw pointer is unsafe and unsafe operations are not allowed in const fn
+  --> $DIR/min_const_fn_unsafe_feature_gate.rs:50:60
+   |
+LL | const unsafe fn foo30_4(x: *mut usize) -> &'static usize { &*x } //~ ERROR not allowed in const fn
+   |                                                            ^^^ dereference of raw pointer
+   |
+   = note: raw pointers may be NULL, dangling or unaligned; they can violate aliasing rules and cause data races: all of these are undefined behavior
+
 error: access to union field is unsafe and unsafe operations are not allowed in const fn
-  --> $DIR/min_const_fn_unsafe_feature_gate.rs:54:5
+  --> $DIR/min_const_fn_unsafe_feature_gate.rs:57:5
    |
 LL |     Foo { x: () }.y //~ ERROR not allowed in const fn
    |     ^^^^^^^^^^^^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
-error: aborting due to 7 previous errors
+error: aborting due to 9 previous errors
 
 For more information about this error, try `rustc --explain E0658`.