Rollup of 3 pull requests

compiler/rustc_feature/src/unstable.rs

@@ -256,6 +256,8 @@ declare_features! (
     (internal, cfg_target_has_reliable_f16_f128, "1.88.0", None),
     /// Allows identifying the `compiler_builtins` crate.
     (internal, compiler_builtins, "1.13.0", None),
+    /// Allows skipping `ConstParamTy_` trait implementation checks
+    (internal, const_param_ty_unchecked, "CURRENT_RUSTC_VERSION", None),
     /// Allows writing custom MIR
     (internal, custom_mir, "1.65.0", None),
     /// Implementation details of externally implementable items

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -856,7 +856,12 @@ fn check_param_wf(tcx: TyCtxt<'_>, param: &ty::GenericParamDef) -> Result<(), Er
             let span = tcx.def_span(param.def_id);
             let def_id = param.def_id.expect_local();
 
-            if tcx.features().adt_const_params() || tcx.features().min_adt_const_params() {
+            if tcx.features().const_param_ty_unchecked() {
+                enter_wf_checking_ctxt(tcx, tcx.local_parent(def_id), |wfcx| {
+                    wfcx.register_wf_obligation(span, None, ty.into());
+                    Ok(())
+                })
+            } else if tcx.features().adt_const_params() || tcx.features().min_adt_const_params() {
                 enter_wf_checking_ctxt(tcx, tcx.local_parent(def_id), |wfcx| {
                     wfcx.register_bound(
                         ObligationCause::new(span, def_id, ObligationCauseCode::ConstParam(ty)),
@@ -1363,12 +1368,14 @@ pub(super) fn check_type_const<'tcx>(
     let tcx = wfcx.tcx();
     let span = tcx.def_span(def_id);
 
-    wfcx.register_bound(
-        ObligationCause::new(span, def_id, ObligationCauseCode::ConstParam(item_ty)),
-        wfcx.param_env,
-        item_ty,
-        tcx.require_lang_item(LangItem::ConstParamTy, span),
-    );
+    if !tcx.features().const_param_ty_unchecked() {
+        wfcx.register_bound(
+            ObligationCause::new(span, def_id, ObligationCauseCode::ConstParam(item_ty)),
+            wfcx.param_env,
+            item_ty,
+            tcx.require_lang_item(LangItem::ConstParamTy, span),
+        );
+    }
 
     if has_value {
         let raw_ct = tcx.const_of_item(def_id).instantiate_identity();

compiler/rustc_hir_analysis/src/coherence/builtin.rs

@@ -184,6 +184,10 @@ fn visit_implementation_of_const_param_ty(checker: &Checker<'_>) -> Result<(), E
         return Ok(());
     }
 
+    if tcx.features().const_param_ty_unchecked() {
+        return Ok(());
+    }
+
     if !tcx.features().adt_const_params() {
         match *self_type.kind() {
             ty::Adt(adt, _) if adt.is_struct() => {

compiler/rustc_span/src/symbol.rs

@@ -680,6 +680,7 @@ symbols! {
         const_panic,
         const_panic_fmt,
         const_param_ty,
+        const_param_ty_unchecked,
         const_precise_live_drops,
         const_ptr_cast,
         const_raw_ptr_deref,

compiler/rustc_trait_selection/src/traits/wf.rs

@@ -574,6 +574,11 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
         if self.tcx().is_lang_item(def_id, LangItem::Sized) {
             return Default::default();
         }
+        if self.tcx().is_lang_item(def_id, LangItem::ConstParamTy)
+            && self.tcx().features().const_param_ty_unchecked()
+        {
+            return Default::default();
+        }
 
         let predicates = self.tcx().predicates_of(def_id);
         let mut origins = vec![def_id; predicates.predicates.len()];

library/core/src/char/methods.rs

@@ -1050,8 +1050,9 @@ impl char {
     /// ```
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_const_stable(feature = "const_is_control", since = "CURRENT_RUSTC_VERSION")]
     #[inline]
-    pub fn is_control(self) -> bool {
+    pub const fn is_control(self) -> bool {
         // According to
         // https://www.unicode.org/policies/stability_policy.html#Property_Value,
         // the set of codepoints in `Cc` will never change.

library/core/src/ffi/va_list.rs

@@ -422,6 +422,7 @@ impl<'f> VaList<'f> {
     /// [`c_void`]: core::ffi::c_void
     #[inline] // Avoid codegen when not used to help backends that don't support VaList.
     #[rustc_const_unstable(feature = "const_c_variadic", issue = "151787")]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub const unsafe fn next_arg<T: VaArgSafe>(&mut self) -> T {
         // SAFETY: the caller must uphold the safety contract for `va_arg`.
         unsafe { va_arg(self) }

src/tools/miri/tests/fail/c-variadic.rs

@@ -1,10 +1,8 @@
 #![feature(c_variadic)]
 
-//@error-in-other-file: Undefined Behavior: more C-variadic arguments read than were passed
-
 fn read_too_many() {
     unsafe extern "C" fn variadic(mut ap: ...) {
-        ap.next_arg::<i32>();
+        ap.next_arg::<i32>(); //~ERROR: more C-variadic arguments read than were passed
     }
 
     unsafe { variadic() };

src/tools/miri/tests/fail/c-variadic.stderr

@@ -1,19 +1,17 @@
 error: Undefined Behavior: more C-variadic arguments read than were passed
-  --> RUSTLIB/core/src/ffi/va_list.rs:LL:CC
+  --> tests/fail/c-variadic.rs:LL:CC
    |
-LL |         unsafe { va_arg(self) }
-   |                  ^^^^^^^^^^^^ Undefined Behavior occurred here
+LL |         ap.next_arg::<i32>();
+   |         ^^^^^^^^^^^^^^^^^^^^ Undefined Behavior occurred here
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
    = note: stack backtrace:
-           0: std::ffi::VaList::<'_>::next_arg
-               at RUSTLIB/core/src/ffi/va_list.rs:LL:CC
-           1: read_too_many::variadic
+           0: read_too_many::variadic
                at tests/fail/c-variadic.rs:LL:CC
-           2: read_too_many
+           1: read_too_many
                at tests/fail/c-variadic.rs:LL:CC
-           3: main
+           2: main
                at tests/fail/c-variadic.rs:LL:CC
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace

tests/ui/const-generics/adt_const_params/const_param_ty_unchecked-unsupported.rs

@@ -0,0 +1,19 @@
+//! Ensure we don't allow Vec<[u8]> as const parameter even with
+//! `const_param_ty_unchecked` feature.
+#![allow(incomplete_features)]
+#![feature(adt_const_params, const_param_ty_unchecked, const_param_ty_trait)]
+use std::marker::ConstParamTy_;
+
+struct VectorOfBytes {
+    a: Vec<[u8]>
+    //~^ ERROR: the size for values of type `[u8]` cannot be known at compilation time [E0277]
+}
+impl ConstParamTy_ for VectorOfBytes {}
+
+fn bar<const N: VectorOfBytes>() {}
+fn foo<const N: Vec<[u8]>>() {}
+    //~^ ERROR: the size for values of type `[u8]` cannot be known at compilation time [E0277]
+    //~| ERROR: the size for values of type `[u8]` cannot be known at compilation time [E0277]
+
+
+fn main() {}

tests/ui/const-generics/adt_const_params/const_param_ty_unchecked-unsupported.stderr

@@ -0,0 +1,34 @@
+error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
+  --> $DIR/const_param_ty_unchecked-unsupported.rs:8:8
+   |
+LL |     a: Vec<[u8]>
+   |        ^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u8]`
+note: required by an implicit `Sized` bound in `Vec`
+  --> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
+
+error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
+  --> $DIR/const_param_ty_unchecked-unsupported.rs:14:8
+   |
+LL | fn foo<const N: Vec<[u8]>>() {}
+   |        ^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u8]`
+note: required by an implicit `Sized` bound in `Vec`
+  --> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
+
+error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
+  --> $DIR/const_param_ty_unchecked-unsupported.rs:14:8
+   |
+LL | fn foo<const N: Vec<[u8]>>() {}
+   |        ^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u8]`
+note: required by an implicit `Sized` bound in `Vec`
+  --> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0277`.

tests/ui/const-generics/adt_const_params/const_param_ty_unchecked.rs

@@ -0,0 +1,26 @@
+//@run-pass
+//! Ensure that const_param_ty_unchecked gate allow
+//! bypassing `ConstParamTy_` implementation check
+
+#![allow(dead_code, incomplete_features)]
+#![feature(const_param_ty_unchecked, const_param_ty_trait)]
+
+use std::marker::ConstParamTy_;
+
+struct Miow;
+
+struct Meoww(Miow);
+
+struct Float {
+    float: f32,
+}
+
+impl ConstParamTy_ for Meoww {}
+impl ConstParamTy_ for Float {}
+
+fn something2<const N: *mut u8>() {}
+fn something<const N: f64>(a: f64) -> f64 {
+    N + a
+}
+
+fn main() {}

tests/ui/const-generics/adt_const_params/const_param_ty_unchecked_fail.rs

@@ -0,0 +1,31 @@
+// gate-test-const_param_ty_unchecked
+//! Ensure this fails when const_param_ty_unchecked isn't used
+#![allow(incomplete_features)]
+#![feature(const_param_ty_trait)]
+
+use std::marker::ConstParamTy_;
+
+struct Miow;
+
+struct Meoww(Miow);
+
+struct Float {
+    float: f32,
+}
+
+impl ConstParamTy_ for Meoww {}
+                    //~^ ERROR: the trait `ConstParamTy_` cannot be implemented for this type [E0204]
+impl ConstParamTy_ for Float {}
+                    //~^ ERROR: the trait `ConstParamTy_` cannot be implemented for this type [E0204]
+
+fn something2<const N: *mut u8>() {}
+                   //~^ ERROR: using raw pointers as const generic parameters is forbidden
+fn something<const N: f64>(a: f64) -> f64 {
+                   //~^ ERROR: `f64` is forbidden as the type of a const generic parameter
+    N + a
+}
+fn foo<const N: Vec<[u8]>>() {}
+    //~^  ERROR: the size for values of type `[u8]` cannot be known at compilation time [E0277]
+          //~^^ ERROR: `Vec<[u8]>` is forbidden as the type of a const generic parameter
+
+fn main() {}

tests/ui/const-generics/adt_const_params/const_param_ty_unchecked_fail.stderr

@@ -0,0 +1,56 @@
+error[E0204]: the trait `ConstParamTy_` cannot be implemented for this type
+  --> $DIR/const_param_ty_unchecked_fail.rs:16:24
+   |
+LL | struct Meoww(Miow);
+   |              ---- this field does not implement `ConstParamTy_`
+...
+LL | impl ConstParamTy_ for Meoww {}
+   |                        ^^^^^
+
+error[E0204]: the trait `ConstParamTy_` cannot be implemented for this type
+  --> $DIR/const_param_ty_unchecked_fail.rs:18:24
+   |
+LL |     float: f32,
+   |     ---------- this field does not implement `ConstParamTy_`
+...
+LL | impl ConstParamTy_ for Float {}
+   |                        ^^^^^
+
+error: using raw pointers as const generic parameters is forbidden
+  --> $DIR/const_param_ty_unchecked_fail.rs:21:24
+   |
+LL | fn something2<const N: *mut u8>() {}
+   |                        ^^^^^^^
+   |
+   = note: the only supported types are integers, `bool`, and `char`
+
+error: `f64` is forbidden as the type of a const generic parameter
+  --> $DIR/const_param_ty_unchecked_fail.rs:23:23
+   |
+LL | fn something<const N: f64>(a: f64) -> f64 {
+   |                       ^^^
+   |
+   = note: the only supported types are integers, `bool`, and `char`
+
+error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
+  --> $DIR/const_param_ty_unchecked_fail.rs:27:8
+   |
+LL | fn foo<const N: Vec<[u8]>>() {}
+   |        ^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u8]`
+note: required by an implicit `Sized` bound in `Vec`
+  --> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
+
+error: `Vec<[u8]>` is forbidden as the type of a const generic parameter
+  --> $DIR/const_param_ty_unchecked_fail.rs:27:17
+   |
+LL | fn foo<const N: Vec<[u8]>>() {}
+   |                 ^^^^^^^^^
+   |
+   = note: the only supported types are integers, `bool`, and `char`
+
+error: aborting due to 6 previous errors
+
+Some errors have detailed explanations: E0204, E0277.
+For more information about an error, try `rustc --explain E0204`.