Rollup of 10 pull requests

compiler/rustc_error_codes/src/error_codes/E0530.md

@@ -1,32 +1,57 @@
 A binding shadowed something it shouldn't.
 
-Erroneous code example:
+A match arm or a variable has a name that is already used by
+something else, e.g.
+
+* struct name
+* enum variant
+* static
+* associated constant
+
+This error may also happen when an enum variant *with fields* is used
+in a pattern, but without its fields.
+
+```compile_fail
+enum Enum {
+    WithField(i32)
+}
+
+use Enum::*;
+match WithField(1) {
+    WithField => {} // error: missing (_)
+}
+```
+
+Match bindings cannot shadow statics:
 
 ```compile_fail,E0530
 static TEST: i32 = 0;
 
-let r: (i32, i32) = (0, 0);
+let r = 123;
 match r {
-    TEST => {} // error: match bindings cannot shadow statics
+    TEST => {} // error: name of a static
 }
 ```
 
-To fix this error, just change the binding's name in order to avoid shadowing
-one of the following:
+Fixed examples:
 
-* struct name
-* struct/enum variant
-* static
-* const
-* associated const
+```
+static TEST: i32 = 0;
 
-Fixed example:
+let r = 123;
+match r {
+    some_value => {} // ok!
+}
+```
+
+or
 
 ```
-static TEST: i32 = 0;
+const TEST: i32 = 0; // const, not static
 
-let r: (i32, i32) = (0, 0);
+let r = 123;
 match r {
-    something => {} // ok!
+    TEST => {} // const is ok!
+    other_values => {}
 }
 ```

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -245,9 +245,10 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 if let ObligationCauseCode::WellFormed(Some(wf_loc)) =
                     root_obligation.cause.code.peel_derives()
                 {
-                    if let Some(cause) =
-                        self.tcx.diagnostic_hir_wf_check((obligation.predicate, wf_loc.clone()))
-                    {
+                    if let Some(cause) = self.tcx.diagnostic_hir_wf_check((
+                        tcx.erase_regions(obligation.predicate),
+                        wf_loc.clone(),
+                    )) {
                         obligation.cause = cause;
                         span = obligation.cause.span;
                     }

compiler/rustc_typeck/src/check/wfcheck.rs

@@ -194,12 +194,13 @@ pub fn check_trait_item(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
     let trait_item = tcx.hir().expect_trait_item(hir_id);
 
-    let method_sig = match trait_item.kind {
-        hir::TraitItemKind::Fn(ref sig, _) => Some(sig),
-        _ => None,
+    let (method_sig, span) = match trait_item.kind {
+        hir::TraitItemKind::Fn(ref sig, _) => (Some(sig), trait_item.span),
+        hir::TraitItemKind::Type(_bounds, Some(ty)) => (None, ty.span),
+        _ => (None, trait_item.span),
     };
     check_object_unsafe_self_trait_by_name(tcx, &trait_item);
-    check_associated_item(tcx, trait_item.hir_id(), trait_item.span, method_sig);
+    check_associated_item(tcx, trait_item.hir_id(), span, method_sig);
 }
 
 fn could_be_self(trait_def_id: LocalDefId, ty: &hir::Ty<'_>) -> bool {
@@ -268,12 +269,13 @@ pub fn check_impl_item(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
     let impl_item = tcx.hir().expect_impl_item(hir_id);
 
-    let method_sig = match impl_item.kind {
-        hir::ImplItemKind::Fn(ref sig, _) => Some(sig),
-        _ => None,
+    let (method_sig, span) = match impl_item.kind {
+        hir::ImplItemKind::Fn(ref sig, _) => (Some(sig), impl_item.span),
+        hir::ImplItemKind::TyAlias(ty) => (None, ty.span),
+        _ => (None, impl_item.span),
     };
 
-    check_associated_item(tcx, impl_item.hir_id(), impl_item.span, method_sig);
+    check_associated_item(tcx, impl_item.hir_id(), span, method_sig);
 }
 
 fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) {

compiler/rustc_typeck/src/collect/type_of.rs

@@ -190,8 +190,12 @@ pub(super) fn opt_const_param_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<
                 // Try to use the segment resolution if it is valid, otherwise we
                 // default to the path resolution.
                 let res = segment.res.filter(|&r| r != Res::Err).unwrap_or(path.res);
+                use def::CtorOf;
                 let generics = match res {
-                    Res::Def(DefKind::Ctor(..), def_id) => {
+                    Res::Def(DefKind::Ctor(CtorOf::Variant, _), def_id) => tcx.generics_of(
+                        tcx.parent(def_id).and_then(|def_id| tcx.parent(def_id)).unwrap(),
+                    ),
+                    Res::Def(DefKind::Variant | DefKind::Ctor(CtorOf::Struct, _), def_id) => {
                         tcx.generics_of(tcx.parent(def_id).unwrap())
                     }
                     // Other `DefKind`s don't have generics and would ICE when calling
@@ -200,7 +204,6 @@ pub(super) fn opt_const_param_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<
                         DefKind::Struct
                         | DefKind::Union
                         | DefKind::Enum
-                        | DefKind::Variant
                         | DefKind::Trait
                         | DefKind::OpaqueTy
                         | DefKind::TyAlias

library/core/src/convert/num.rs

@@ -45,7 +45,8 @@ impl_float_to_int!(f64 => u8 u16 u32 u64 u128 usize i8 i16 i32 i64 i128 isize);
 macro_rules! impl_from {
     ($Small: ty, $Large: ty, #[$attr:meta], $doc: expr) => {
         #[$attr]
-        impl From<$Small> for $Large {
+        #[rustc_const_unstable(feature = "const_num_from_num", issue = "87852")]
+        impl const From<$Small> for $Large {
             // Rustdocs on the impl block show a "[+] show undocumented items" toggle.
             // Rustdocs on functions do not.
             #[doc = $doc]
@@ -172,7 +173,8 @@ impl_from! { f32, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0"
 macro_rules! try_from_unbounded {
     ($source:ty, $($target:ty),*) => {$(
         #[stable(feature = "try_from", since = "1.34.0")]
-        impl TryFrom<$source> for $target {
+        #[rustc_const_unstable(feature = "const_num_from_num", issue = "87852")]
+        impl const TryFrom<$source> for $target {
             type Error = TryFromIntError;
 
             /// Try to create the target number type from a source
@@ -190,7 +192,8 @@ macro_rules! try_from_unbounded {
 macro_rules! try_from_lower_bounded {
     ($source:ty, $($target:ty),*) => {$(
         #[stable(feature = "try_from", since = "1.34.0")]
-        impl TryFrom<$source> for $target {
+        #[rustc_const_unstable(feature = "const_num_from_num", issue = "87852")]
+        impl const TryFrom<$source> for $target {
             type Error = TryFromIntError;
 
             /// Try to create the target number type from a source
@@ -212,7 +215,8 @@ macro_rules! try_from_lower_bounded {
 macro_rules! try_from_upper_bounded {
     ($source:ty, $($target:ty),*) => {$(
         #[stable(feature = "try_from", since = "1.34.0")]
-        impl TryFrom<$source> for $target {
+        #[rustc_const_unstable(feature = "const_num_from_num", issue = "87852")]
+        impl const TryFrom<$source> for $target {
             type Error = TryFromIntError;
 
             /// Try to create the target number type from a source
@@ -234,7 +238,8 @@ macro_rules! try_from_upper_bounded {
 macro_rules! try_from_both_bounded {
     ($source:ty, $($target:ty),*) => {$(
         #[stable(feature = "try_from", since = "1.34.0")]
-        impl TryFrom<$source> for $target {
+        #[rustc_const_unstable(feature = "const_num_from_num", issue = "87852")]
+        impl const TryFrom<$source> for $target {
             type Error = TryFromIntError;
 
             /// Try to create the target number type from a source

library/core/src/lib.rs

@@ -99,6 +99,7 @@
 #![feature(const_slice_from_raw_parts)]
 #![feature(const_slice_ptr_len)]
 #![feature(const_swap)]
+#![feature(const_trait_impl)]
 #![feature(const_type_id)]
 #![feature(const_type_name)]
 #![feature(const_unreachable_unchecked)]

library/core/src/option.rs

@@ -1399,6 +1399,33 @@ impl<T> Option<T> {
     }
 }
 
+impl<T, U> Option<(T, U)> {
+    /// Unzips an option containing a tuple of two options
+    ///
+    /// If `self` is `Some((a, b))` this method returns `(Some(a), Some(b))`.
+    /// Otherwise, `(None, None)` is returned.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(unzip_option)]
+    ///
+    /// let x = Some((1, "hi"));
+    /// let y = None::<(u8, u32)>;
+    ///
+    /// assert_eq!(x.unzip(), (Some(1), Some("hi")));
+    /// assert_eq!(y.unzip(), (None, None));
+    /// ```
+    #[inline]
+    #[unstable(feature = "unzip_option", issue = "87800", reason = "recently added")]
+    pub const fn unzip(self) -> (Option<T>, Option<U>) {
+        match self {
+            Some((a, b)) => (Some(a), Some(b)),
+            None => (None, None),
+        }
+    }
+}
+
 impl<T: Copy> Option<&T> {
     /// Maps an `Option<&T>` to an `Option<T>` by copying the contents of the
     /// option.

library/core/tests/lib.rs

@@ -13,6 +13,8 @@
 #![feature(const_ptr_read)]
 #![feature(const_ptr_write)]
 #![feature(const_ptr_offset)]
+#![feature(const_trait_impl)]
+#![feature(const_num_from_num)]
 #![feature(core_intrinsics)]
 #![feature(core_private_bignum)]
 #![feature(core_private_diy_float)]
@@ -66,6 +68,7 @@
 #![feature(slice_group_by)]
 #![feature(trusted_random_access)]
 #![feature(unsize)]
+#![feature(unzip_option)]
 #![deny(unsafe_op_in_unsafe_fn)]
 
 extern crate test;

library/core/tests/num/const_from.rs

@@ -0,0 +1,25 @@
+#[test]
+fn from() {
+    use core::convert::TryFrom;
+    use core::num::TryFromIntError;
+
+    // From
+    const FROM: i64 = i64::from(1i32);
+    assert_eq!(FROM, 1i64);
+
+    // From int to float
+    const FROM_F64: f64 = f64::from(42u8);
+    assert_eq!(FROM_F64, 42f64);
+
+    // Upper bounded
+    const U8_FROM_U16: Result<u8, TryFromIntError> = u8::try_from(1u16);
+    assert_eq!(U8_FROM_U16, Ok(1u8));
+
+    // Both bounded
+    const I8_FROM_I16: Result<i8, TryFromIntError> = i8::try_from(1i16);
+    assert_eq!(I8_FROM_I16, Ok(1i8));
+
+    // Lower bounded
+    const I16_FROM_U16: Result<i16, TryFromIntError> = i16::try_from(1u16);
+    assert_eq!(I16_FROM_U16, Ok(1i16));
+}

library/core/tests/num/mod.rs

@@ -27,6 +27,8 @@ mod u64;
 mod u8;
 
 mod bignum;
+
+mod const_from;
 mod dec2flt;
 mod flt2dec;
 mod int_log;

library/core/tests/option.rs

@@ -399,11 +399,43 @@ fn test_unwrap_drop() {
 }
 
 #[test]
-pub fn option_ext() {
+fn option_ext() {
     let thing = "{{ f }}";
     let f = thing.find("{{");
 
     if f.is_none() {
         println!("None!");
     }
 }
+
+#[test]
+fn zip_options() {
+    let x = Some(10);
+    let y = Some("foo");
+    let z: Option<usize> = None;
+
+    assert_eq!(x.zip(y), Some((10, "foo")));
+    assert_eq!(x.zip(z), None);
+    assert_eq!(z.zip(x), None);
+}
+
+#[test]
+fn unzip_options() {
+    let x = Some((10, "foo"));
+    let y = None::<(bool, i32)>;
+
+    assert_eq!(x.unzip(), (Some(10), Some("foo")));
+    assert_eq!(y.unzip(), (None, None));
+}
+
+#[test]
+fn zip_unzip_roundtrip() {
+    let x = Some(10);
+    let y = Some("foo");
+
+    let z = x.zip(y);
+    assert_eq!(z, Some((10, "foo")));
+
+    let a = z.unzip();
+    assert_eq!(a, (x, y));
+}