Rollup merge of rust-lang#57067 - Centril:stabilize-min_const_unsafe_fn, r=oli-obk

Stabilize min_const_unsafe_fn in 1.33

Fixes rust-lang#55607

r? @oli-obk

Author: Centril

src/librustc/ich/impls_mir.rs

@@ -47,7 +47,6 @@ impl_stable_hash_for!(enum mir::BorrowKind {
 impl_stable_hash_for!(enum mir::UnsafetyViolationKind {
     General,
     GeneralAndConstFn,
-    GatedConstFnCall,
     ExternStatic(lint_node_id),
     BorrowPacked(lint_node_id),
 });

src/librustc/mir/mod.rs

@@ -2792,9 +2792,6 @@ impl Location {
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
 pub enum UnsafetyViolationKind {
     General,
-    /// Right now function calls to `const unsafe fn` are only permitted behind a feature gate
-    /// Also, even `const unsafe fn` need an `unsafe` block to do the allowed operations.
-    GatedConstFnCall,
     /// Permitted in const fn and regular fns
     GeneralAndConstFn,
     ExternStatic(ast::NodeId),

src/librustc_mir/transform/check_unsafety.rs

@@ -23,7 +23,6 @@ use rustc::mir::visit::{PlaceContext, Visitor, MutatingUseContext};
 
 use syntax::ast;
 use syntax::symbol::Symbol;
-use syntax::feature_gate::{emit_feature_err, GateIssue};
 
 use std::ops::Bound;
 
@@ -97,7 +96,7 @@ impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
                 if let hir::Unsafety::Unsafe = sig.unsafety() {
                     self.require_unsafe("call to unsafe function",
                         "consult the function's documentation for information on how to avoid \
-                         undefined behavior", UnsafetyViolationKind::GatedConstFnCall)
+                         undefined behavior", UnsafetyViolationKind::GeneralAndConstFn)
                 }
             }
         }
@@ -325,11 +324,6 @@ impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
                             // compat lint
                             violation.kind = UnsafetyViolationKind::General;
                         },
-                        UnsafetyViolationKind::GatedConstFnCall => {
-                            // safe code can't call unsafe const fns, this `UnsafetyViolationKind`
-                            // is only relevant for `Safety::ExplicitUnsafe` in `unsafe const fn`s
-                            violation.kind = UnsafetyViolationKind::General;
-                        }
                     }
                     if !self.violations.contains(&violation) {
                         self.violations.push(violation)
@@ -346,19 +340,8 @@ impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
                 }
                 // only some unsafety is allowed in const fn
                 if self.min_const_fn {
-                    let min_const_unsafe_fn = self.tcx.features().min_const_unsafe_fn;
                     for violation in violations {
                         match violation.kind {
-                            UnsafetyViolationKind::GatedConstFnCall if min_const_unsafe_fn => {
-                                // these function calls to unsafe functions are allowed
-                                // if `#![feature(min_const_unsafe_fn)]` is active
-                            },
-                            UnsafetyViolationKind::GatedConstFnCall => {
-                                // without the feature gate, we report errors
-                                if !self.violations.contains(&violation) {
-                                    self.violations.push(violation.clone())
-                                }
-                            }
                             // these unsafe things are stable in const fn
                             UnsafetyViolationKind::GeneralAndConstFn => {},
                             // these things are forbidden in const fns
@@ -620,16 +603,6 @@ pub fn check_unsafety<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
                     .note(&details.as_str()[..])
                     .emit();
             }
-            UnsafetyViolationKind::GatedConstFnCall => {
-                emit_feature_err(
-                    &tcx.sess.parse_sess,
-                    "min_const_unsafe_fn",
-                    source_info.span,
-                    GateIssue::Language,
-                    "calls to `const unsafe fn` in const fns are unstable",
-                );
-
-            }
             UnsafetyViolationKind::ExternStatic(lint_node_id) => {
                 tcx.lint_node_note(SAFE_EXTERN_STATICS,
                               lint_node_id,

src/libstd/lib.rs

@@ -273,7 +273,6 @@
 #![feature(libc)]
 #![feature(link_args)]
 #![feature(linkage)]
-#![cfg_attr(not(stage0), feature(min_const_unsafe_fn))]
 #![feature(needs_panic_runtime)]
 #![feature(never_type)]
 #![feature(nll)]

src/libsyntax/feature_gate.rs

@@ -486,9 +486,6 @@ declare_features! (
 
     // `extern crate self as foo;` puts local crate root into extern prelude under name `foo`.
     (active, extern_crate_self, "1.31.0", Some(56409), None),
-
-    // Allows calling `const unsafe fn` inside `unsafe` blocks in `const fn` functions.
-    (active, min_const_unsafe_fn, "1.31.0", Some(55607), None),
 );
 
 declare_features! (
@@ -694,6 +691,8 @@ declare_features! (
     (accepted, underscore_imports, "1.33.0", Some(48216), None),
     // Allows `#[repr(packed(N))]` attribute on structs.
     (accepted, repr_packed, "1.33.0", Some(33158), None),
+    // Allows calling `const unsafe fn` inside `unsafe` blocks in `const fn` functions.
+    (accepted, min_const_unsafe_fn, "1.33.0", Some(55607), None),
 );
 
 // If you change this, please modify `src/doc/unstable-book` as well. You must

src/test/run-pass-fulldeps/newtype_index.rs

@@ -1,4 +1,4 @@
-#![feature(rustc_attrs, rustc_private, step_trait, min_const_unsafe_fn)]
+#![feature(rustc_attrs, rustc_private, step_trait)]
 
 #[macro_use] extern crate rustc_data_structures;
 extern crate rustc_serialize;

src/test/rustdoc/const-display.rs

@@ -15,7 +15,6 @@
             issue = "0")]
 
 #![feature(rustc_const_unstable, const_fn, foo, foo2)]
-#![feature(min_const_unsafe_fn)]
 #![feature(staged_api)]
 
 // @has 'foo/fn.foo.html' '//pre' 'pub unsafe fn foo() -> u32'

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

@@ -8,27 +8,62 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// gate-test-min_const_unsafe_fn
+//------------------------------------------------------------------------------
+// OK
+//------------------------------------------------------------------------------
 
-// ok
 const unsafe fn ret_i32_no_unsafe() -> i32 { 42 }
 const unsafe fn ret_null_ptr_no_unsafe<T>() -> *const T { 0 as *const T }
 const unsafe fn ret_null_mut_ptr_no_unsafe<T>() -> *mut T { 0 as *mut T }
 const fn no_unsafe() { unsafe {} }
 
-// not ok
 const fn call_unsafe_const_fn() -> i32 {
-    unsafe { ret_i32_no_unsafe() } //~ ERROR calls to `const unsafe fn` in const fns are unstable
+    unsafe { ret_i32_no_unsafe() }
 }
 const fn call_unsafe_generic_const_fn() -> *const String {
     unsafe { ret_null_ptr_no_unsafe::<String>() }
-    //~^ ERROR calls to `const unsafe fn` in const fns are unstable
 }
-const fn call_unsafe_generic_cell_const_fn() -> *const Vec<std::cell::Cell<u32>> {
+const fn call_unsafe_generic_cell_const_fn()
+    -> *const Vec<std::cell::Cell<u32>>
+{
     unsafe { ret_null_mut_ptr_no_unsafe::<Vec<std::cell::Cell<u32>>>() }
-    //~^ ERROR calls to `const unsafe fn` in const fns
 }
-const unsafe fn deref_forbidden(x: *mut usize) -> usize { *x }
+
+const unsafe fn call_unsafe_const_unsafe_fn() -> i32 {
+    unsafe { ret_i32_no_unsafe() }
+}
+const unsafe fn call_unsafe_generic_const_unsafe_fn() -> *const String {
+    unsafe { ret_null_ptr_no_unsafe::<String>() }
+}
+const unsafe fn call_unsafe_generic_cell_const_unsafe_fn()
+    -> *const Vec<std::cell::Cell<u32>>
+{
+    unsafe { ret_null_mut_ptr_no_unsafe::<Vec<std::cell::Cell<u32>>>() }
+}
+
+const unsafe fn call_unsafe_const_unsafe_fn_immediate() -> i32 {
+    ret_i32_no_unsafe()
+}
+const unsafe fn call_unsafe_generic_const_unsafe_fn_immediate() -> *const String {
+    ret_null_ptr_no_unsafe::<String>()
+}
+const unsafe fn call_unsafe_generic_cell_const_unsafe_fn_immediate()
+    -> *const Vec<std::cell::Cell<u32>>
+{
+    ret_null_mut_ptr_no_unsafe::<Vec<std::cell::Cell<u32>>>()
+}
+
+//------------------------------------------------------------------------------
+// NOT OK
+//------------------------------------------------------------------------------
+
+const fn bad_const_fn_deref_raw(x: *mut usize) -> &'static usize { unsafe { &*x } } //~ is unsafe
+//~^ dereferencing raw pointers in constant functions
+
+const unsafe fn bad_const_unsafe_deref_raw(x: *mut usize) -> usize { *x }
+//~^ dereferencing raw pointers in constant functions
+
+const unsafe fn bad_const_unsafe_deref_raw_ref(x: *mut usize) -> &'static usize { &*x }
 //~^ dereferencing raw pointers in constant functions
 
 fn main() {}

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

@@ -1,43 +1,44 @@
 error[E0658]: dereferencing raw pointers in constant functions is unstable (see issue #51911)
-  --> $DIR/min_const_fn_unsafe.rs:31:59
+  --> $DIR/min_const_fn_unsafe.rs:60:77
    |
-LL | const unsafe fn deref_forbidden(x: *mut usize) -> usize { *x }
-   |                                                           ^^
+LL | const fn bad_const_fn_deref_raw(x: *mut usize) -> &'static usize { unsafe { &*x } } //~ is unsafe
+   |                                                                             ^^^
    |
    = 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.rs:38:5
+error[E0658]: dereferencing raw pointers in constant functions is unstable (see issue #51911)
+  --> $DIR/min_const_fn_unsafe.rs:63:70
    |
-LL |     Foo { x: () }.y
-   |     ^^^^^^^^^^^^^^^
+LL | const unsafe fn bad_const_unsafe_deref_raw(x: *mut usize) -> usize { *x }
+   |                                                                      ^^
    |
-   = help: add #![feature(const_fn_union)] to the crate attributes to enable
+   = help: add #![feature(const_raw_ptr_deref)] to the crate attributes to enable
 
-error[E0658]: calls to `const unsafe fn` in const fns are unstable (see issue #55607)
-  --> $DIR/min_const_fn_unsafe.rs:21:14
+error[E0658]: dereferencing raw pointers in constant functions is unstable (see issue #51911)
+  --> $DIR/min_const_fn_unsafe.rs:66:83
    |
-LL |     unsafe { ret_i32_no_unsafe() } //~ ERROR calls to `const unsafe fn` in const fns are unstable
-   |              ^^^^^^^^^^^^^^^^^^^
+LL | const unsafe fn bad_const_unsafe_deref_raw_ref(x: *mut usize) -> &'static usize { &*x }
+   |                                                                                   ^^^
    |
-   = help: add #![feature(min_const_unsafe_fn)] to the crate attributes to enable
+   = help: add #![feature(const_raw_ptr_deref)] to the crate attributes to enable
 
-error[E0658]: calls to `const unsafe fn` in const fns are unstable (see issue #55607)
-  --> $DIR/min_const_fn_unsafe.rs:24:14
+error[E0658]: unions in const fn are unstable (see issue #51909)
+  --> $DIR/min_const_fn_unsafe.rs:73:5
    |
-LL |     unsafe { ret_null_ptr_no_unsafe::<String>() }
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     Foo { x: () }.y
+   |     ^^^^^^^^^^^^^^^
    |
-   = help: add #![feature(min_const_unsafe_fn)] to the crate attributes to enable
+   = help: add #![feature(const_fn_union)] to the crate attributes to enable
 
-error[E0658]: calls to `const unsafe fn` in const fns are unstable (see issue #55607)
-  --> $DIR/min_const_fn_unsafe.rs:28:14
+error[E0133]: dereference of raw pointer is unsafe and requires unsafe function or block
+  --> $DIR/min_const_fn_unsafe.rs:60:77
    |
-LL |     unsafe { ret_null_mut_ptr_no_unsafe::<Vec<std::cell::Cell<u32>>>() }
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | const fn bad_const_fn_deref_raw(x: *mut usize) -> &'static usize { unsafe { &*x } } //~ is unsafe
+   |                                                                             ^^^ dereference of raw pointer
    |
-   = help: add #![feature(min_const_unsafe_fn)] to the crate attributes to enable
+   = 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: aborting due to 5 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
+Some errors occurred: E0133, E0658.
+For more information about an error, try `rustc --explain E0133`.