Check user type annotations for range patterns.

This commit builds on the fix from rust-lang#58161 (which fixed miscompilation
caused by the introduction of `AscribeUserType` patterns for associated
constants) to start checking these patterns are well-formed for ranges
(previous fix just ignored them so that miscompilation wouldn't occur).

Author: davidtwco

src/librustc_mir/build/matches/mod.rs

@@ -7,7 +7,7 @@ use crate::build::scope::{CachedBlock, DropKind};
 use crate::build::ForGuard::{self, OutsideGuard, RefWithinGuard, ValWithinGuard};
 use crate::build::{BlockAnd, BlockAndExtension, Builder};
 use crate::build::{GuardFrame, GuardFrameLocal, LocalsForNode};
-use crate::hair::*;
+use crate::hair::{self, *};
 use rustc::mir::*;
 use rustc::ty::{self, CanonicalUserTypeAnnotation, Ty};
 use rustc::ty::layout::VariantIdx;
@@ -283,9 +283,11 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                     },
                     ..
                 },
-                user_ty: pat_ascription_ty,
-                variance: _,
-                user_ty_span,
+                ascription: hair::pattern::Ascription {
+                    user_ty: pat_ascription_ty,
+                    variance: _,
+                    user_ty_span,
+                },
             } => {
                 let place =
                     self.storage_live_binding(block, var, irrefutable_pat.span, OutsideGuard);
@@ -560,9 +562,11 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             }
             PatternKind::AscribeUserType {
                 ref subpattern,
-                ref user_ty,
-                user_ty_span,
-                variance: _,
+                ascription: hair::pattern::Ascription {
+                    ref user_ty,
+                    user_ty_span,
+                    variance: _,
+                },
             } => {
                 // This corresponds to something like
                 //

src/librustc_mir/build/matches/simplify.rs

@@ -14,7 +14,7 @@
 
 use crate::build::Builder;
 use crate::build::matches::{Ascription, Binding, MatchPair, Candidate};
-use crate::hair::*;
+use crate::hair::{self, *};
 use rustc::ty;
 use rustc::ty::layout::{Integer, IntegerExt, Size};
 use syntax::attr::{SignedInt, UnsignedInt};
@@ -58,9 +58,11 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         match *match_pair.pattern.kind {
             PatternKind::AscribeUserType {
                 ref subpattern,
-                variance,
-                ref user_ty,
-                user_ty_span
+                ascription: hair::pattern::Ascription {
+                    variance,
+                    ref user_ty,
+                    user_ty_span,
+                },
             } => {
                 // Apply the type ascription to the value at `match_pair.place`, which is the
                 // value being matched, taking the variance field into account.

src/librustc_mir/hair/cx/block.rs

@@ -1,4 +1,4 @@
-use crate::hair::*;
+use crate::hair::{self, *};
 use crate::hair::cx::Cx;
 use crate::hair::cx::to_ref::ToRef;
 use rustc::middle::region;
@@ -83,10 +83,12 @@ fn mirror_stmts<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                             ty: pattern.ty,
                             span: pattern.span,
                             kind: Box::new(PatternKind::AscribeUserType {
-                                user_ty: PatternTypeProjection::from_user_type(user_ty),
-                                user_ty_span: ty.span,
+                                ascription: hair::pattern::Ascription {
+                                    user_ty: PatternTypeProjection::from_user_type(user_ty),
+                                    user_ty_span: ty.span,
+                                    variance: ty::Variance::Covariant,
+                                },
                                 subpattern: pattern,
-                                variance: ty::Variance::Covariant,
                             })
                         };
                     }

src/librustc_mir/hair/pattern/_match.rs

@@ -871,18 +871,24 @@ impl<'tcx> IntRange<'tcx> {
     }
 
     fn from_pat(tcx: TyCtxt<'_, 'tcx, 'tcx>,
-                pat: &Pattern<'tcx>)
+                mut pat: &Pattern<'tcx>)
                 -> Option<IntRange<'tcx>> {
-        Self::from_ctor(tcx, &match pat.kind {
-            box PatternKind::Constant { value } => ConstantValue(value),
-            box PatternKind::Range(PatternRange { lo, hi, ty, end }) => ConstantRange(
-                lo.to_bits(tcx, ty::ParamEnv::empty().and(ty)).unwrap(),
-                hi.to_bits(tcx, ty::ParamEnv::empty().and(ty)).unwrap(),
-                ty,
-                end,
-            ),
-            _ => return None,
-        })
+        let range = loop {
+            match pat.kind {
+                box PatternKind::Constant { value } => break ConstantValue(value),
+                box PatternKind::Range(PatternRange { lo, hi, ty, end }) => break ConstantRange(
+                    lo.to_bits(tcx, ty::ParamEnv::empty().and(ty)).unwrap(),
+                    hi.to_bits(tcx, ty::ParamEnv::empty().and(ty)).unwrap(),
+                    ty,
+                    end,
+                ),
+                box PatternKind::AscribeUserType { ref subpattern, .. } => {
+                    pat = subpattern;
+                },
+                _ => return None,
+            }
+        };
+        Self::from_ctor(tcx, &range)
     }
 
     // The return value of `signed_bias` should be XORed with an endpoint to encode/decode it.

src/librustc_mir/hair/pattern/mod.rs

@@ -58,7 +58,7 @@ pub struct Pattern<'tcx> {
 }
 
 
-#[derive(Clone, Debug)]
+#[derive(Copy, Clone, Debug, PartialEq)]
 pub struct PatternTypeProjection<'tcx> {
     pub user_ty: CanonicalUserType<'tcx>,
 }
@@ -87,33 +87,38 @@ impl<'tcx> PatternTypeProjection<'tcx> {
     }
 }
 
+#[derive(Copy, Clone, Debug, PartialEq)]
+pub struct Ascription<'tcx> {
+    pub user_ty: PatternTypeProjection<'tcx>,
+    /// Variance to use when relating the type `user_ty` to the **type of the value being
+    /// matched**. Typically, this is `Variance::Covariant`, since the value being matched must
+    /// have a type that is some subtype of the ascribed type.
+    ///
+    /// Note that this variance does not apply for any bindings within subpatterns. The type
+    /// assigned to those bindings must be exactly equal to the `user_ty` given here.
+    ///
+    /// The only place where this field is not `Covariant` is when matching constants, where
+    /// we currently use `Contravariant` -- this is because the constant type just needs to
+    /// be "comparable" to the type of the input value. So, for example:
+    ///
+    /// ```text
+    /// match x { "foo" => .. }
+    /// ```
+    ///
+    /// requires that `&'static str <: T_x`, where `T_x` is the type of `x`. Really, we should
+    /// probably be checking for a `PartialEq` impl instead, but this preserves the behavior
+    /// of the old type-check for now. See #57280 for details.
+    pub variance: ty::Variance,
+    pub user_ty_span: Span,
+}
+
 #[derive(Clone, Debug)]
 pub enum PatternKind<'tcx> {
     Wild,
 
     AscribeUserType {
-        user_ty: PatternTypeProjection<'tcx>,
+        ascription: Ascription<'tcx>,
         subpattern: Pattern<'tcx>,
-        /// Variance to use when relating the type `user_ty` to the **type of the value being
-        /// matched**. Typically, this is `Variance::Covariant`, since the value being matched must
-        /// have a type that is some subtype of the ascribed type.
-        ///
-        /// Note that this variance does not apply for any bindings within subpatterns. The type
-        /// assigned to those bindings must be exactly equal to the `user_ty` given here.
-        ///
-        /// The only place where this field is not `Covariant` is when matching constants, where
-        /// we currently use `Contravariant` -- this is because the constant type just needs to
-        /// be "comparable" to the type of the input value. So, for example:
-        ///
-        /// ```text
-        /// match x { "foo" => .. }
-        /// ```
-        ///
-        /// requires that `&'static str <: T_x`, where `T_x` is the type of `x`. Really, we should
-        /// probably be checking for a `PartialEq` impl instead, but this preserves the behavior
-        /// of the old type-check for now. See #57280 for details.
-        variance: ty::Variance,
-        user_ty_span: Span,
     },
 
     /// x, ref x, x @ P, etc
@@ -167,18 +172,7 @@ pub enum PatternKind<'tcx> {
     },
 }
 
-impl<'tcx> PatternKind<'tcx> {
-    /// If this is a `PatternKind::AscribeUserType` then return the subpattern kind, otherwise
-    /// return this pattern kind.
-    fn with_user_type_ascription_subpattern(self) -> Self {
-        match self {
-            PatternKind::AscribeUserType { subpattern: Pattern { box kind, ..  }, ..  } => kind,
-            kind => kind,
-        }
-    }
-}
-
-#[derive(Clone, Copy, Debug, PartialEq)]
+#[derive(Copy, Clone, Debug, PartialEq)]
 pub struct PatternRange<'tcx> {
     pub lo: ty::Const<'tcx>,
     pub hi: ty::Const<'tcx>,
@@ -405,6 +399,19 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
             )
     }
 
+    fn lower_range_expr(
+        &mut self,
+        expr: &'tcx hir::Expr,
+    ) -> (PatternKind<'tcx>, Option<Ascription<'tcx>>) {
+        match self.lower_lit(expr) {
+            PatternKind::AscribeUserType {
+                ascription: lo_ascription,
+                subpattern: Pattern { kind: box kind, .. },
+            } => (kind, Some(lo_ascription)),
+            kind => (kind, None),
+        }
+    }
+
     fn lower_pattern_unadjusted(&mut self, pat: &'tcx hir::Pat) -> Pattern<'tcx> {
         let mut ty = self.tables.node_id_to_type(pat.hir_id);
 
@@ -414,14 +421,10 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
             PatKind::Lit(ref value) => self.lower_lit(value),
 
             PatKind::Range(ref lo_expr, ref hi_expr, end) => {
-                match (
-                    // Look for `PatternKind::Constant` patterns inside of any
-                    // `PatternKind::AscribeUserType` patterns. Type ascriptions can be safely
-                    // ignored for the purposes of lowering a range correctly - these are checked
-                    // elsewhere for well-formedness.
-                    self.lower_lit(lo_expr).with_user_type_ascription_subpattern(),
-                    self.lower_lit(hi_expr).with_user_type_ascription_subpattern(),
-                ) {
+                let (lo, lo_ascription) = self.lower_range_expr(lo_expr);
+                let (hi, hi_ascription) = self.lower_range_expr(hi_expr);
+
+                let mut kind = match (lo, hi) {
                     (PatternKind::Constant { value: lo }, PatternKind::Constant { value: hi }) => {
                         use std::cmp::Ordering;
                         let cmp = compare_const_vals(
@@ -470,17 +473,33 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
                                 PatternKind::Wild
                             }
                         }
-                    }
+                    },
                     ref pats => {
                         self.tcx.sess.delay_span_bug(
                             pat.span,
-                            &format!("found bad range pattern `{:?}` outside of error recovery",
-                                     pats),
+                            &format!(
+                                "found bad range pattern `{:?}` outside of error recovery",
+                                pats,
+                            ),
                         );
 
                         PatternKind::Wild
+                    },
+                };
+
+                // If we are handling a range with associated constants (e.g.
+                // `Foo::<'a>::A..=Foo::B`), we need to put the ascriptions for the associated
+                // constants somewhere. Have them on the range pattern.
+                for ascription in &[lo_ascription, hi_ascription] {
+                    if let Some(ascription) = ascription {
+                        kind = PatternKind::AscribeUserType {
+                            ascription: *ascription,
+                            subpattern: Pattern { span: pat.span, ty, kind: Box::new(kind), },
+                        };
                     }
                 }
+
+                kind
             }
 
             PatKind::Path(ref qpath) => {
@@ -756,9 +775,11 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
                     ty,
                     kind: Box::new(kind),
                 },
-                user_ty: PatternTypeProjection::from_user_type(user_ty),
-                user_ty_span: span,
-                variance: ty::Variance::Covariant,
+                ascription: Ascription {
+                    user_ty: PatternTypeProjection::from_user_type(user_ty),
+                    user_ty_span: span,
+                    variance: ty::Variance::Covariant,
+                },
             };
         }
 
@@ -808,11 +829,13 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
                                         kind: Box::new(
                                             PatternKind::AscribeUserType {
                                                 subpattern: pattern,
-                                                /// Note that use `Contravariant` here. See the
-                                                /// `variance` field documentation for details.
-                                                variance: ty::Variance::Contravariant,
-                                                user_ty,
-                                                user_ty_span: span,
+                                                ascription: Ascription {
+                                                    /// Note that use `Contravariant` here. See the
+                                                    /// `variance` field documentation for details.
+                                                    variance: ty::Variance::Contravariant,
+                                                    user_ty,
+                                                    user_ty_span: span,
+                                                },
                                             }
                                         ),
                                         ty: value.ty,
@@ -1105,14 +1128,18 @@ impl<'tcx> PatternFoldable<'tcx> for PatternKind<'tcx> {
             PatternKind::Wild => PatternKind::Wild,
             PatternKind::AscribeUserType {
                 ref subpattern,
-                variance,
-                ref user_ty,
-                user_ty_span,
+                ascription: Ascription {
+                    variance,
+                    ref user_ty,
+                    user_ty_span,
+                },
             } => PatternKind::AscribeUserType {
                 subpattern: subpattern.fold_with(folder),
-                user_ty: user_ty.fold_with(folder),
-                variance,
-                user_ty_span,
+                ascription: Ascription {
+                    user_ty: user_ty.fold_with(folder),
+                    variance,
+                    user_ty_span,
+                },
             },
             PatternKind::Binding {
                 mutability,

src/test/ui/nll/issue-58299.rs

@@ -0,0 +1,30 @@
+#![allow(dead_code)]
+#![feature(nll)]
+
+struct A<'a>(&'a ());
+
+trait Y {
+    const X: i32;
+}
+
+impl Y for A<'static> {
+    const X: i32 = 10;
+}
+
+fn foo<'a>(x: i32) {
+    match x {
+        // This uses <A<'a> as Y>::X, but `A<'a>` does not implement `Y`.
+        A::<'a>::X..=A::<'static>::X => (), //~ ERROR lifetime may not live long enough
+        _ => (),
+    }
+}
+
+fn bar<'a>(x: i32) {
+    match x {
+        // This uses <A<'a> as Y>::X, but `A<'a>` does not implement `Y`.
+        A::<'static>::X..=A::<'a>::X => (), //~ ERROR lifetime may not live long enough
+        _ => (),
+    }
+}
+
+fn main() {}

src/test/ui/nll/issue-58299.stderr

@@ -0,0 +1,20 @@
+error: lifetime may not live long enough
+  --> $DIR/issue-58299.rs:17:9
+   |
+LL | fn foo<'a>(x: i32) {
+   |        -- lifetime `'a` defined here
+...
+LL |         A::<'a>::X..=A::<'static>::X => (), //~ ERROR lifetime may not live long enough
+   |         ^^^^^^^^^^ requires that `'a` must outlive `'static`
+
+error: lifetime may not live long enough
+  --> $DIR/issue-58299.rs:25:27
+   |
+LL | fn bar<'a>(x: i32) {
+   |        -- lifetime `'a` defined here
+...
+LL |         A::<'static>::X..=A::<'a>::X => (), //~ ERROR lifetime may not live long enough
+   |                           ^^^^^^^^^^ requires that `'a` must outlive `'static`
+
+error: aborting due to 2 previous errors
+