Auto merge of #156113 - JonathanBrouwer:rollup-yXpNY1L, r=JonathanBrouwer

Rollup of 3 pull requests

Successful merges:

 - #153536 (Add `const_param_ty_unchecked` gate)
 - #155528 (const-stabilize `char::is_control()`)
 - #156086 (VaList::next_arg: track_caller for better Miri errors)

Author: bors

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() {}