Rollup of 4 pull requests

src/liballoc/lib.rs

@@ -63,6 +63,7 @@
 #![warn(missing_debug_implementations)]
 #![deny(intra_doc_link_resolution_failure)] // rustdoc is run without -D warnings
 #![allow(explicit_outlives_requirements)]
+#![cfg_attr(not(bootstrap), allow(incomplete_features))]
 
 #![cfg_attr(not(test), feature(generator_trait))]
 #![cfg_attr(test, feature(test))]

src/libcore/any.rs

@@ -468,7 +468,8 @@ impl TypeId {
 /// The current implementation uses the same infrastructure as compiler
 /// diagnostics and debuginfo, but this is not guaranteed.
 #[stable(feature = "type_name", since = "1.38.0")]
-pub fn type_name<T: ?Sized>() -> &'static str {
+#[rustc_const_unstable(feature = "const_type_name")]
+pub const fn type_name<T: ?Sized>() -> &'static str {
     #[cfg(bootstrap)]
     unsafe {
         intrinsics::type_name::<T>()

src/libcore/lib.rs

@@ -63,6 +63,7 @@
 #![warn(missing_debug_implementations)]
 #![deny(intra_doc_link_resolution_failure)] // rustdoc is run without -D warnings
 #![allow(explicit_outlives_requirements)]
+#![cfg_attr(not(bootstrap), allow(incomplete_features))]
 
 #![feature(allow_internal_unstable)]
 #![feature(arbitrary_self_types)]

src/librustc_lint/builtin.rs

@@ -33,13 +33,12 @@ use lint::{LintPass, LateLintPass, EarlyLintPass, EarlyContext};
 use rustc::util::nodemap::FxHashSet;
 
 use syntax::tokenstream::{TokenTree, TokenStream};
-use syntax::ast;
+use syntax::ast::{self, Expr};
 use syntax::ptr::P;
-use syntax::ast::Expr;
 use syntax::attr::{self, HasAttrs, AttributeTemplate};
 use syntax::source_map::Spanned;
 use syntax::edition::Edition;
-use syntax::feature_gate::{AttributeGate, AttributeType};
+use syntax::feature_gate::{self, AttributeGate, AttributeType};
 use syntax::feature_gate::{Stability, deprecated_attributes};
 use syntax_pos::{BytePos, Span, SyntaxContext};
 use syntax::symbol::{Symbol, kw, sym};
@@ -1831,3 +1830,35 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
         }
     }
 }
+
+declare_lint! {
+    pub INCOMPLETE_FEATURES,
+    Warn,
+    "incomplete features that may function improperly in some or all cases"
+}
+
+declare_lint_pass!(
+    /// Check for used feature gates in `INCOMPLETE_FEATURES` in `feature_gate.rs`.
+    IncompleteFeatures => [INCOMPLETE_FEATURES]
+);
+
+impl EarlyLintPass for IncompleteFeatures {
+    fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
+        let features = cx.sess.features_untracked();
+        features.declared_lang_features
+            .iter().map(|(name, span, _)| (name, span))
+            .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
+            .filter(|(name, _)| feature_gate::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
+            .for_each(|(name, &span)| {
+                cx.struct_span_lint(
+                    INCOMPLETE_FEATURES,
+                    span,
+                    &format!(
+                        "the feature `{}` is incomplete and may cause the compiler to crash",
+                        name,
+                    )
+                )
+                .emit();
+            });
+    }
+}

src/librustc_lint/lib.rs

@@ -97,6 +97,7 @@ macro_rules! early_lint_passes {
             DeprecatedAttr: DeprecatedAttr::new(),
             WhileTrue: WhileTrue,
             NonAsciiIdents: NonAsciiIdents,
+            IncompleteFeatures: IncompleteFeatures,
         ]);
     )
 }

src/libsyntax/feature_gate.rs

@@ -569,10 +569,10 @@ declare_features! (
     // -------------------------------------------------------------------------
 );
 
-// Some features are known to be incomplete and using them is likely to have
-// unanticipated results, such as compiler crashes. We warn the user about these
-// to alert them.
-const INCOMPLETE_FEATURES: &[Symbol] = &[
+/// Some features are known to be incomplete and using them is likely to have
+/// unanticipated results, such as compiler crashes. We warn the user about these
+/// to alert them.
+pub const INCOMPLETE_FEATURES: &[Symbol] = &[
     sym::impl_trait_in_bindings,
     sym::generic_associated_types,
     sym::const_generics,
@@ -2338,15 +2338,6 @@ pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
             }
 
             let name = mi.name_or_empty();
-            if INCOMPLETE_FEATURES.iter().any(|f| name == *f) {
-                span_handler.struct_span_warn(
-                    mi.span(),
-                    &format!(
-                        "the feature `{}` is incomplete and may cause the compiler to crash",
-                        name
-                    )
-                ).emit();
-            }
 
             if let Some(edition) = ALL_EDITIONS.iter().find(|e| name == e.feature_name()) {
                 if *edition <= crate_edition {

src/test/ui/array-slice-vec/subslice-patterns-pass.rs

@@ -0,0 +1,128 @@
+// This test comprehensively checks the passing static and dynamic semantics
+// of subslice patterns `..`, `x @ ..`, `ref x @ ..`, and `ref mut @ ..`
+// in slice patterns `[$($pat), $(,)?]` .
+
+// run-pass
+
+#![feature(slice_patterns)]
+
+#![allow(unreachable_patterns)]
+
+use std::convert::identity;
+
+#[derive(PartialEq, Debug, Clone)]
+struct N(u8);
+
+macro_rules! n {
+    ($($e:expr),* $(,)?) => {
+        [$(N($e)),*]
+    }
+}
+
+macro_rules! c {
+    ($inp:expr, $typ:ty, $out:expr $(,)?) => {
+        assert_eq!($out, identity::<$typ>($inp));
+    }
+}
+
+macro_rules! m {
+    ($e:expr, $p:pat => $b:expr) => {
+        match $e {
+            $p => $b,
+            _ => panic!(),
+        }
+    }
+}
+
+fn main() {
+    slices();
+    arrays();
+}
+
+fn slices() {
+    // Matching slices using `ref` patterns:
+    let mut v = vec![N(0), N(1), N(2), N(3), N(4)];
+    let mut vc = (0..=4).collect::<Vec<u8>>();
+
+    let [..] = v[..]; // Always matches.
+    m!(v[..], [N(0), ref sub @ .., N(4)] => c!(sub, &[N], n![1, 2, 3]));
+    m!(v[..], [N(0), ref sub @ ..] => c!(sub, &[N], n![1, 2, 3, 4]));
+    m!(v[..], [ref sub @ .., N(4)] => c!(sub, &[N], n![0, 1, 2, 3]));
+    m!(v[..], [ref sub @ .., _, _, _, _, _] => c!(sub, &[N], &n![] as &[N]));
+    m!(v[..], [_, _, _, _, _, ref sub @ ..] => c!(sub, &[N], &n![] as &[N]));
+    m!(vc[..], [x, .., y] => c!((x, y), (u8, u8), (0, 4)));
+
+    // Matching slices using `ref mut` patterns:
+    let [..] = v[..]; // Always matches.
+    m!(v[..], [N(0), ref mut sub @ .., N(4)] => c!(sub, &mut [N], n![1, 2, 3]));
+    m!(v[..], [N(0), ref mut sub @ ..] => c!(sub, &mut [N], n![1, 2, 3, 4]));
+    m!(v[..], [ref mut sub @ .., N(4)] => c!(sub, &mut [N], n![0, 1, 2, 3]));
+    m!(v[..], [ref mut sub @ .., _, _, _, _, _] => c!(sub, &mut [N], &mut n![] as &mut [N]));
+    m!(v[..], [_, _, _, _, _, ref mut sub @ ..] => c!(sub, &mut [N], &mut n![] as &mut [N]));
+    m!(vc[..], [x, .., y] => c!((x, y), (u8, u8), (0, 4)));
+
+    // Matching slices using default binding modes (&):
+    let [..] = &v[..]; // Always matches.
+    m!(&v[..], [N(0), sub @ .., N(4)] => c!(sub, &[N], n![1, 2, 3]));
+    m!(&v[..], [N(0), sub @ ..] => c!(sub, &[N], n![1, 2, 3, 4]));
+    m!(&v[..], [sub @ .., N(4)] => c!(sub, &[N], n![0, 1, 2, 3]));
+    m!(&v[..], [sub @ .., _, _, _, _, _] => c!(sub, &[N], &n![] as &[N]));
+    m!(&v[..], [_, _, _, _, _, sub @ ..] => c!(sub, &[N], &n![] as &[N]));
+    m!(&vc[..], [x, .., y] => c!((x, y), (&u8, &u8), (&0, &4)));
+
+    // Matching slices using default binding modes (&mut):
+    let [..] = &mut v[..]; // Always matches.
+    m!(&mut v[..], [N(0), sub @ .., N(4)] => c!(sub, &mut [N], n![1, 2, 3]));
+    m!(&mut v[..], [N(0), sub @ ..] => c!(sub, &mut [N], n![1, 2, 3, 4]));
+    m!(&mut v[..], [sub @ .., N(4)] => c!(sub, &mut [N], n![0, 1, 2, 3]));
+    m!(&mut v[..], [sub @ .., _, _, _, _, _] => c!(sub, &mut [N], &mut n![] as &mut [N]));
+    m!(&mut v[..], [_, _, _, _, _, sub @ ..] => c!(sub, &mut [N], &mut n![] as &mut [N]));
+    m!(&mut vc[..], [x, .., y] => c!((x, y), (&mut u8, &mut u8), (&mut 0, &mut 4)));
+}
+
+fn arrays() {
+    let mut v = n![0, 1, 2, 3, 4];
+    let vc = [0, 1, 2, 3, 4];
+
+    // Matching arrays by value:
+    m!(v.clone(), [N(0), sub @ .., N(4)] => c!(sub, [N; 3], n![1, 2, 3]));
+    m!(v.clone(), [N(0), sub @ ..] => c!(sub, [N; 4], n![1, 2, 3, 4]));
+    m!(v.clone(), [sub @ .., N(4)] => c!(sub, [N; 4], n![0, 1, 2, 3]));
+    m!(v.clone(), [sub @ .., _, _, _, _, _] => c!(sub, [N; 0], n![] as [N; 0]));
+    m!(v.clone(), [_, _, _, _, _, sub @ ..] => c!(sub, [N; 0], n![] as [N; 0]));
+    m!(v.clone(), [x, .., y] => c!((x, y), (N, N), (N(0), N(4))));
+    m!(v.clone(), [..] => ());
+
+    // Matching arrays by ref patterns:
+    m!(v, [N(0), ref sub @ .., N(4)] => c!(sub, &[N; 3], &n![1, 2, 3]));
+    m!(v, [N(0), ref sub @ ..] => c!(sub, &[N; 4], &n![1, 2, 3, 4]));
+    m!(v, [ref sub @ .., N(4)] => c!(sub, &[N; 4], &n![0, 1, 2, 3]));
+    m!(v, [ref sub @ .., _, _, _, _, _] => c!(sub, &[N; 0], &n![] as &[N; 0]));
+    m!(v, [_, _, _, _, _, ref sub @ ..] => c!(sub, &[N; 0], &n![] as &[N; 0]));
+    m!(vc, [x, .., y] => c!((x, y), (u8, u8), (0, 4)));
+
+    // Matching arrays by ref mut patterns:
+    m!(v, [N(0), ref mut sub @ .., N(4)] => c!(sub, &mut [N; 3], &mut n![1, 2, 3]));
+    m!(v, [N(0), ref mut sub @ ..] => c!(sub, &mut [N; 4], &mut n![1, 2, 3, 4]));
+    m!(v, [ref mut sub @ .., N(4)] => c!(sub, &mut [N; 4], &mut n![0, 1, 2, 3]));
+    m!(v, [ref mut sub @ .., _, _, _, _, _] => c!(sub, &mut [N; 0], &mut n![] as &mut [N; 0]));
+    m!(v, [_, _, _, _, _, ref mut sub @ ..] => c!(sub, &mut [N; 0], &mut n![] as &mut [N; 0]));
+
+    // Matching arrays by default binding modes (&):
+    m!(&v, [N(0), sub @ .., N(4)] => c!(sub, &[N; 3], &n![1, 2, 3]));
+    m!(&v, [N(0), sub @ ..] => c!(sub, &[N; 4], &n![1, 2, 3, 4]));
+    m!(&v, [sub @ .., N(4)] => c!(sub, &[N; 4], &n![0, 1, 2, 3]));
+    m!(&v, [sub @ .., _, _, _, _, _] => c!(sub, &[N; 0], &n![] as &[N; 0]));
+    m!(&v, [_, _, _, _, _, sub @ ..] => c!(sub, &[N; 0], &n![] as &[N; 0]));
+    m!(&v, [..] => ());
+    m!(&v, [x, .., y] => c!((x, y), (&N, &N), (&N(0), &N(4))));
+
+    // Matching arrays by default binding modes (&mut):
+    m!(&mut v, [N(0), sub @ .., N(4)] => c!(sub, &mut [N; 3], &mut n![1, 2, 3]));
+    m!(&mut v, [N(0), sub @ ..] => c!(sub, &mut [N; 4], &mut n![1, 2, 3, 4]));
+    m!(&mut v, [sub @ .., N(4)] => c!(sub, &mut [N; 4], &mut n![0, 1, 2, 3]));
+    m!(&mut v, [sub @ .., _, _, _, _, _] => c!(sub, &mut [N; 0], &mut n![] as &[N; 0]));
+    m!(&mut v, [_, _, _, _, _, sub @ ..] => c!(sub, &mut [N; 0], &mut n![] as &[N; 0]));
+    m!(&mut v, [..] => ());
+    m!(&mut v, [x, .., y] => c!((x, y), (&mut N, &mut N), (&mut N(0), &mut N(4))));
+}

src/test/ui/associated-type-bounds/duplicate.stderr

@@ -3,6 +3,8 @@ warning: the feature `impl_trait_in_bindings` is incomplete and may cause the co
    |
 LL | #![feature(impl_trait_in_bindings)]
    |            ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 
 error[E0719]: the value of the associated type `Item` (from the trait `std::iter::Iterator`) is already specified
   --> $DIR/duplicate.rs:12:36

src/test/ui/associated-type-bounds/dyn-lcsit.stderr

@@ -3,4 +3,6 @@ warning: the feature `impl_trait_in_bindings` is incomplete and may cause the co
    |
 LL | #![feature(impl_trait_in_bindings)]
    |            ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/associated-type-bounds/lcsit.stderr

@@ -3,4 +3,6 @@ warning: the feature `impl_trait_in_bindings` is incomplete and may cause the co
    |
 LL | #![feature(impl_trait_in_bindings)]
    |            ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/apit-with-const-param.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/array-wrapper-struct-ctor.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/broken-mir-1.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/broken-mir-2.stderr

@@ -3,6 +3,8 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 
 error[E0277]: arrays only have std trait implementations for lengths 0..=32
   --> $DIR/broken-mir-2.rs:7:36

src/test/ui/const-generics/cannot-infer-const-args.stderr

@@ -3,6 +3,8 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 
 error[E0282]: type annotations needed
   --> $DIR/cannot-infer-const-args.rs:9:5

src/test/ui/const-generics/cannot-infer-type-for-const-param.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/concrete-const-as-fn-arg.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/concrete-const-impl-method.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/condition-in-trait-const-arg.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/const-arg-in-fn.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/const-expression-parameter.stderr

@@ -9,6 +9,8 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 
 error: aborting due to previous error
 

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

@@ -1,9 +1,3 @@
-warning: the feature `const_generics` is incomplete and may cause the compiler to crash
-  --> $DIR/const-fn-with-const-param.rs:1:12
-   |
-LL | #![feature(const_generics)]
-   |            ^^^^^^^^^^^^^^
-
 error: const parameters are not permitted in `const fn`
   --> $DIR/const-fn-with-const-param.rs:4:1
    |
@@ -13,5 +7,13 @@ LL | |     X
 LL | | }
    | |_^
 
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/const-fn-with-const-param.rs:1:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
 error: aborting due to previous error
 

src/test/ui/const-generics/const-generic-array-wrapper.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/const-param-before-other-params.rs

@@ -1,5 +1,4 @@
 #![feature(const_generics)]
-//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
 
 fn bar<const X: (), 'a>(_: &'a ()) {
     //~^ ERROR lifetime parameters must be declared prior to const parameters