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Stabilize casts and coercions to &[T]
in const fn
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@ -527,7 +527,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
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size: Size::ZERO,
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}),
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// Potentially-fat pointers.
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// Potentially-wide pointers.
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ty::Ref(_, pointee, _) | ty::RawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
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let mut data_ptr = scalar_unit(Pointer);
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if !ty.is_unsafe_ptr() {
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@ -191,8 +191,17 @@ fn check_rvalue(
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_,
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_,
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) => Err((span, "function pointer casts are not allowed in const fn".into())),
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Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), _, _) => {
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Err((span, "unsizing casts are not allowed in const fn".into()))
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Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), op, cast_ty) => {
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let pointee_ty = cast_ty.builtin_deref(true).unwrap().ty;
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let unsized_ty = tcx.struct_tail_erasing_lifetimes(pointee_ty, tcx.param_env(def_id));
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if let ty::Slice(_) | ty::Str = unsized_ty.kind {
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check_operand(tcx, op, span, def_id, body)?;
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// Casting/coercing things to slices is fine.
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Ok(())
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} else {
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// We just can't allow trait objects until we have figured out trait method calls.
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Err((span, "unsizing casts are not allowed in const fn".into()))
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}
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}
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// binops are fine on integers
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Rvalue::BinaryOp(_, lhs, rhs) | Rvalue::CheckedBinaryOp(_, lhs, rhs) => {
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13
src/test/ui/consts/array-to-slice-cast.rs
Normal file
13
src/test/ui/consts/array-to-slice-cast.rs
Normal file
@ -0,0 +1,13 @@
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// check-pass
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fn main() {}
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const fn foo() {
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let x = [1, 2, 3, 4, 5];
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let y: &[_] = &x;
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struct Foo<T: ?Sized>(bool, T);
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let x: Foo<[u8; 3]> = Foo(true, [1, 2, 3]);
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let y: &Foo<[u8]> = &x;
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}
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@ -1,7 +1,6 @@
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#![feature(const_extern_fn)]
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const extern fn unsize(x: &[u8; 3]) -> &[u8] { x }
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//~^ ERROR unsizing casts are not allowed in const fn
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const unsafe extern "C" fn closure() -> fn() { || {} }
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//~^ ERROR function pointers in const fn are unstable
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const unsafe extern fn use_float() { 1.0 + 1.0; }
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@ -1,14 +1,5 @@
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error[E0723]: unsizing casts are not allowed in const fn
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--> $DIR/const-extern-fn-min-const-fn.rs:3:48
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LL | const extern fn unsize(x: &[u8; 3]) -> &[u8] { x }
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| ^
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= note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
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= help: add `#![feature(const_fn)]` to the crate attributes to enable
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error[E0723]: function pointers in const fn are unstable
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--> $DIR/const-extern-fn-min-const-fn.rs:5:41
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--> $DIR/const-extern-fn-min-const-fn.rs:4:41
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LL | const unsafe extern "C" fn closure() -> fn() { || {} }
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| ^^^^
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@ -17,7 +8,7 @@ LL | const unsafe extern "C" fn closure() -> fn() { || {} }
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= help: add `#![feature(const_fn)]` to the crate attributes to enable
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error[E0723]: only int, `bool` and `char` operations are stable in const fn
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--> $DIR/const-extern-fn-min-const-fn.rs:7:38
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--> $DIR/const-extern-fn-min-const-fn.rs:6:38
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LL | const unsafe extern fn use_float() { 1.0 + 1.0; }
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| ^^^^^^^^^
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@ -26,7 +17,7 @@ LL | const unsafe extern fn use_float() { 1.0 + 1.0; }
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= help: add `#![feature(const_fn)]` to the crate attributes to enable
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error[E0723]: casting pointers to ints is unstable in const fn
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--> $DIR/const-extern-fn-min-const-fn.rs:9:48
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--> $DIR/const-extern-fn-min-const-fn.rs:8:48
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LL | const extern "C" fn ptr_cast(val: *const u8) { val as usize; }
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| ^^^^^^^^^^^^
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@ -34,6 +25,6 @@ LL | const extern "C" fn ptr_cast(val: *const u8) { val as usize; }
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= note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
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= help: add `#![feature(const_fn)]` to the crate attributes to enable
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error: aborting due to 4 previous errors
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error: aborting due to 3 previous errors
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For more information about this error, try `rustc --explain E0723`.
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@ -1,7 +1,6 @@
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fn main() {}
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const fn unsize(x: &[u8; 3]) -> &[u8] { x }
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//~^ ERROR unsizing casts are not allowed in const fn
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const fn closure() -> fn() { || {} }
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//~^ ERROR function pointers in const fn are unstable
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const fn closure2() {
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@ -1,14 +1,5 @@
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error[E0723]: unsizing casts are not allowed in const fn
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--> $DIR/cast_errors.rs:3:41
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LL | const fn unsize(x: &[u8; 3]) -> &[u8] { x }
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| ^
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= note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
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= help: add `#![feature(const_fn)]` to the crate attributes to enable
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error[E0723]: function pointers in const fn are unstable
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--> $DIR/cast_errors.rs:5:23
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--> $DIR/cast_errors.rs:4:23
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LL | const fn closure() -> fn() { || {} }
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| ^^^^
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@ -17,7 +8,7 @@ LL | const fn closure() -> fn() { || {} }
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= help: add `#![feature(const_fn)]` to the crate attributes to enable
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error[E0723]: function pointers in const fn are unstable
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--> $DIR/cast_errors.rs:8:5
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--> $DIR/cast_errors.rs:7:5
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LL | (|| {}) as fn();
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| ^^^^^^^^^^^^^^^
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@ -26,7 +17,7 @@ LL | (|| {}) as fn();
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= help: add `#![feature(const_fn)]` to the crate attributes to enable
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error[E0723]: function pointers in const fn are unstable
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--> $DIR/cast_errors.rs:11:28
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--> $DIR/cast_errors.rs:10:28
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LL | const fn reify(f: fn()) -> unsafe fn() { f }
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| ^^^^^^^^^^^
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@ -35,7 +26,7 @@ LL | const fn reify(f: fn()) -> unsafe fn() { f }
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= help: add `#![feature(const_fn)]` to the crate attributes to enable
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error[E0723]: function pointers in const fn are unstable
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--> $DIR/cast_errors.rs:13:21
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--> $DIR/cast_errors.rs:12:21
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LL | const fn reify2() { main as unsafe fn(); }
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| ^^^^^^^^^^^^^^^^^^^
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@ -43,6 +34,6 @@ LL | const fn reify2() { main as unsafe fn(); }
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= note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
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= help: add `#![feature(const_fn)]` to the crate attributes to enable
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error: aborting due to 5 previous errors
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error: aborting due to 4 previous errors
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For more information about this error, try `rustc --explain E0723`.
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