Gate use of raw and function pointers in const generics behind

const_compare_raw_pointers.

Author: skinnyBat

src/librustc_typeck/collect.rs

@@ -1508,9 +1508,29 @@ pub fn checked_type_of(tcx: TyCtxt<'_>, def_id: DefId, fail: bool) -> Option<Ty<
         }
 
         Node::GenericParam(param) => match &param.kind {
-            hir::GenericParamKind::Type { default: Some(ref ty), .. } |
-            hir::GenericParamKind::Const { ref ty, .. } => {
-                icx.to_ty(ty)
+            hir::GenericParamKind::Type { default: Some(ref ty), .. } => icx.to_ty(ty),
+            hir::GenericParamKind::Const { ty: ref hir_ty, .. } => {
+                let ty = icx.to_ty(hir_ty);
+                if !tcx.features().const_compare_raw_pointers {
+                    let err = match ty.peel_refs().kind {
+                        ty::FnPtr(_) => Some("function pointers"),
+                        ty::RawPtr(_) => Some("raw pointers"),
+                        _ => None,
+                    };
+                    if let Some(unsupported_type) = err {
+                        feature_gate::emit_feature_err(
+                            &tcx.sess.parse_sess,
+                            sym::const_compare_raw_pointers,
+                            hir_ty.span,
+                            feature_gate::GateIssue::Language,
+                            &format!(
+                                "use of {} as const generic arguments are unstable",
+                                unsupported_type
+                            ),
+                        );
+                    };
+                }
+                ty
             }
             x => {
                 if !fail {

src/test/ui/const-generics/fn-const-param-call.rs

@@ -1,6 +1,6 @@
 // run-pass
 
-#![feature(const_generics)]
+#![feature(const_generics, const_compare_raw_pointers)]
 //~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
 
 fn function() -> u32 {

src/test/ui/const-generics/fn-const-param-call.stderr

@@ -1,7 +1,7 @@
 warning: the feature `const_generics` is incomplete and may cause the compiler to crash
   --> $DIR/fn-const-param-call.rs:3:12
    |
-LL | #![feature(const_generics)]
+LL | #![feature(const_generics, const_compare_raw_pointers)]
    |            ^^^^^^^^^^^^^^
    |
    = note: `#[warn(incomplete_features)]` on by default

src/test/ui/const-generics/fn-const-param-infer.rs

@@ -1,4 +1,4 @@
-#![feature(const_generics)]
+#![feature(const_generics, const_compare_raw_pointers)]
 //~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
 
 struct Checked<const F: fn(usize) -> bool>;

src/test/ui/const-generics/fn-const-param-infer.stderr

@@ -1,7 +1,7 @@
 warning: the feature `const_generics` is incomplete and may cause the compiler to crash
   --> $DIR/fn-const-param-infer.rs:1:12
    |
-LL | #![feature(const_generics)]
+LL | #![feature(const_generics, const_compare_raw_pointers)]
    |            ^^^^^^^^^^^^^^
    |
    = note: `#[warn(incomplete_features)]` on by default

src/test/ui/const-generics/raw-ptr-const-param-deref.rs

@@ -0,0 +1,19 @@
+// run-pass
+#![feature(const_generics, const_compare_raw_pointers)]
+//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
+
+const A: u32 = 3;
+
+struct Const<const P: *const u32>;
+
+impl<const P: *const u32> Const<{P}> {
+    fn get() -> u32 {
+        unsafe {
+            *P
+        }
+    }
+}
+
+fn main() {
+    assert_eq!(Const::<{&A as *const _}>::get(), 3)
+}

src/test/ui/const-generics/raw-ptr-const-param-deref.stderr

@@ -0,0 +1,8 @@
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/raw-ptr-const-param-deref.rs:2:12
+   |
+LL | #![feature(const_generics, const_compare_raw_pointers)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+

src/test/ui/const-generics/raw-ptr-const-param.rs

@@ -0,0 +1,9 @@
+#![feature(const_generics, const_compare_raw_pointers)]
+//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
+
+struct Const<const P: *const u32>;
+
+fn main() {
+    let _: Const<{15 as *const _}> = Const::<{10 as *const _}>; //~ mismatched types
+    let _: Const<{10 as *const _}> = Const::<{10 as *const _}>;
+}

src/test/ui/const-generics/raw-ptr-const-param.stderr

@@ -0,0 +1,20 @@
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/raw-ptr-const-param.rs:1:12
+   |
+LL | #![feature(const_generics, const_compare_raw_pointers)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0308]: mismatched types
+  --> $DIR/raw-ptr-const-param.rs:7:38
+   |
+LL |     let _: Const<{15 as *const _}> = Const::<{10 as *const _}>;
+   |                                      ^^^^^^^^^^^^^^^^^^^^^^^^^ expected `Scalar(0x000000000000000f) : *const u32`, found `Scalar(0x000000000000000a) : *const u32`
+   |
+   = note: expected type `Const<>`
+              found type `Const<>`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/feature-gates/feature-gate-const_generics-ptr.rs

@@ -0,0 +1,9 @@
+struct ConstFn<const F: fn()>;
+//~^ ERROR const generics are unstable
+//~^^ ERROR use of function pointers as const generic arguments are unstable
+
+struct ConstPtr<const P: *const u32>;
+//~^ ERROR const generics are unstable
+//~^^ ERROR use of raw pointers as const generic arguments are unstable
+
+fn main() {}