Add unsized tuple coercions.

Author: qnighy

src/librustc/traits/error_reporting.rs

@@ -1058,7 +1058,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 err.note("slice and array elements must have `Sized` type");
             }
             ObligationCauseCode::TupleElem => {
-                err.note("tuple elements must have `Sized` type");
+                err.note("only the last element of a tuple may have a dynamically sized type");
             }
             ObligationCauseCode::ProjectionWf(data) => {
                 err.note(&format!("required so that the projection `{}` is well-formed",

src/librustc/traits/select.rs

@@ -1655,6 +1655,11 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 def_id_a == def_id_b
             }
 
+            // (.., T) -> (.., U).
+            (&ty::TyTuple(tys_a, _), &ty::TyTuple(tys_b, _)) => {
+                tys_a.len() == tys_b.len()
+            }
+
             _ => false
         };
 
@@ -2614,6 +2619,37 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                     &[inner_target]));
             }
 
+            // (.., T) -> (.., U).
+            (&ty::TyTuple(tys_a, _), &ty::TyTuple(tys_b, _)) => {
+                assert_eq!(tys_a.len(), tys_b.len());
+
+                // The last field of the tuple has to exist.
+                let (a_last, a_mid) = if let Some(x) = tys_a.split_last() {
+                    x
+                } else {
+                    return Err(Unimplemented);
+                };
+                let b_last = tys_b.last().unwrap();
+
+                // Check that the source tuple with the target's
+                // last element is a subtype of the target.
+                let new_tuple = tcx.mk_tup(a_mid.iter().chain(Some(b_last)), false);
+                let InferOk { obligations, .. } =
+                    self.infcx.at(&obligation.cause, obligation.param_env)
+                              .eq(target, new_tuple)
+                              .map_err(|_| Unimplemented)?;
+                self.inferred_obligations.extend(obligations);
+
+                // Construct the nested T: Unsize<U> predicate.
+                nested.push(tcx.predicate_for_trait_def(
+                    obligation.param_env,
+                    obligation.cause.clone(),
+                    obligation.predicate.def_id(),
+                    obligation.recursion_depth + 1,
+                    a_last,
+                    &[b_last]));
+            }
+
             _ => bug!()
         };
 

src/librustc/ty/layout.rs

@@ -1220,12 +1220,16 @@ impl<'a, 'tcx> Layout {
             }
 
             ty::TyTuple(tys, _) => {
-                // FIXME(camlorn): if we ever allow unsized tuples, this needs to be checked.
-                // See the univariant case below to learn how.
+                let kind = if tys.len() == 0 {
+                    StructKind::AlwaysSizedUnivariant
+                } else {
+                    StructKind::MaybeUnsizedUnivariant
+                };
+
                 let st = Struct::new(dl,
                     &tys.iter().map(|ty| ty.layout(tcx, param_env))
                       .collect::<Result<Vec<_>, _>>()?,
-                    &ReprOptions::default(), StructKind::AlwaysSizedUnivariant, ty)?;
+                    &ReprOptions::default(), kind, ty)?;
                 Univariant { variant: st, non_zero: false }
             }
 

src/librustc/ty/util.rs

@@ -317,15 +317,26 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                                  target: Ty<'tcx>)
                                  -> (Ty<'tcx>, Ty<'tcx>) {
         let (mut a, mut b) = (source, target);
-        while let (&TyAdt(a_def, a_substs), &TyAdt(b_def, b_substs)) = (&a.sty, &b.sty) {
-            if a_def != b_def || !a_def.is_struct() {
-                break;
-            }
-            match a_def.struct_variant().fields.last() {
-                Some(f) => {
-                    a = f.ty(self, a_substs);
-                    b = f.ty(self, b_substs);
-                }
+        loop {
+            match (&a.sty, &b.sty) {
+                (&TyAdt(a_def, a_substs), &TyAdt(b_def, b_substs))
+                        if a_def == b_def && a_def.is_struct() => {
+                    if let Some(f) = a_def.struct_variant().fields.last() {
+                        a = f.ty(self, a_substs);
+                        b = f.ty(self, b_substs);
+                    } else {
+                        break;
+                    }
+                },
+                (&TyTuple(a_tys, _), &TyTuple(b_tys, _))
+                        if a_tys.len() == b_tys.len() => {
+                    if let Some(a_last) = a_tys.last() {
+                        a = a_last;
+                        b = b_tys.last().unwrap();
+                    } else {
+                        break;
+                    }
+                },
                 _ => break,
             }
         }

src/librustc_trans/glue.rs

@@ -76,7 +76,7 @@ pub fn size_and_align_of_dst<'a, 'tcx>(bcx: &Builder<'a, 'tcx>, t: Ty<'tcx>, inf
     }
     assert!(!info.is_null());
     match t.sty {
-        ty::TyAdt(def, substs) => {
+        ty::TyAdt(..) | ty::TyTuple(..) => {
             let ccx = bcx.ccx;
             // First get the size of all statically known fields.
             // Don't use size_of because it also rounds up to alignment, which we
@@ -101,8 +101,14 @@ pub fn size_and_align_of_dst<'a, 'tcx>(bcx: &Builder<'a, 'tcx>, t: Ty<'tcx>, inf
 
             // Recurse to get the size of the dynamically sized field (must be
             // the last field).
-            let last_field = def.struct_variant().fields.last().unwrap();
-            let field_ty = monomorphize::field_ty(bcx.tcx(), substs, last_field);
+            let field_ty = match t.sty {
+                ty::TyAdt(def, substs) => {
+                    let last_field = def.struct_variant().fields.last().unwrap();
+                    monomorphize::field_ty(bcx.tcx(), substs, last_field)
+                },
+                ty::TyTuple(tys, _) => tys.last().unwrap(),
+                _ => unreachable!(),
+            };
             let (unsized_size, unsized_align) = size_and_align_of_dst(bcx, field_ty, info);
 
             // FIXME (#26403, #27023): We should be adding padding

src/test/compile-fail/dst-bad-assign-3.rs

@@ -0,0 +1,48 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Forbid assignment into a dynamically sized type.
+
+type Fat<T: ?Sized> = (isize, &'static str, T);
+//~^ WARNING trait bounds are not (yet) enforced
+
+#[derive(PartialEq,Eq)]
+struct Bar;
+
+#[derive(PartialEq,Eq)]
+struct Bar1 {
+    f: isize
+}
+
+trait ToBar {
+    fn to_bar(&self) -> Bar;
+    fn to_val(&self) -> isize;
+}
+
+impl ToBar for Bar1 {
+    fn to_bar(&self) -> Bar {
+        Bar
+    }
+    fn to_val(&self) -> isize {
+        self.f
+    }
+}
+
+pub fn main() {
+    // Assignment.
+    let f5: &mut Fat<ToBar> = &mut (5, "some str", Bar1 {f :42});
+    let z: Box<ToBar> = Box::new(Bar1 {f: 36});
+    f5.2 = Bar1 {f: 36};
+    //~^ ERROR mismatched types
+    //~| expected type `ToBar`
+    //~| found type `Bar1`
+    //~| expected trait ToBar, found struct `Bar1`
+    //~| ERROR `ToBar: std::marker::Sized` is not satisfied
+}

src/test/compile-fail/dst-bad-coerce1.rs

@@ -29,4 +29,16 @@ pub fn main() {
     let f2: &Fat<Foo> = &f1;
     let f3: &Fat<Bar> = f2;
     //~^ ERROR `Foo: Bar` is not satisfied
+
+    // Tuple with a vec of isize.
+    let f1 = ([1, 2, 3],);
+    let f2: &([isize; 3],) = &f1;
+    let f3: &([usize],) = f2;
+    //~^ ERROR mismatched types
+
+    // Tuple with a trait.
+    let f1 = (Foo,);
+    let f2: &(Foo,) = &f1;
+    let f3: &(Bar,) = f2;
+    //~^ ERROR `Foo: Bar` is not satisfied
 }

src/test/compile-fail/dst-bad-coerce2.rs

@@ -28,4 +28,14 @@ pub fn main() {
     let f1 = Fat { ptr: Foo };
     let f2: &Fat<Foo> = &f1;
     let f3: &mut Fat<Bar> = f2; //~ ERROR mismatched types
+
+    // Tuple with a vec of ints.
+    let f1 = ([1, 2, 3],);
+    let f2: &([isize; 3],) = &f1;
+    let f3: &mut ([isize],) = f2; //~ ERROR mismatched types
+
+    // Tuple with a trait.
+    let f1 = (Foo,);
+    let f2: &(Foo,) = &f1;
+    let f3: &mut (Bar,) = f2; //~ ERROR mismatched types
 }

src/test/compile-fail/dst-bad-coerce3.rs

@@ -28,6 +28,16 @@ fn baz<'a>() {
     let f1 = Fat { ptr: Foo };
     let f2: &Fat<Foo> = &f1; //~ ERROR `f1` does not live long enough
     let f3: &'a Fat<Bar> = f2;
+
+    // Tuple with a vec of ints.
+    let f1 = ([1, 2, 3],);
+    let f2: &([isize; 3],) = &f1; //~ ERROR `f1` does not live long enough
+    let f3: &'a ([isize],) = f2;
+
+    // Tuple with a trait.
+    let f1 = (Foo,);
+    let f2: &(Foo,) = &f1; //~ ERROR `f1` does not live long enough
+    let f3: &'a (Bar,) = f2;
 }
 
 pub fn main() {

src/test/compile-fail/dst-bad-coerce4.rs

@@ -22,4 +22,12 @@ pub fn main() {
     //~| expected type `&Fat<[isize; 3]>`
     //~| found type `&Fat<[isize]>`
     //~| expected array of 3 elements, found slice
+
+    // Tuple with a vec of isizes.
+    let f1: &([isize],) = &([1, 2, 3],);
+    let f2: &([isize; 3],) = f1;
+    //~^ ERROR mismatched types
+    //~| expected type `&([isize; 3],)`
+    //~| found type `&([isize],)`
+    //~| expected array of 3 elements, found slice
 }

src/test/compile-fail/dst-bad-deep-2.rs

@@ -0,0 +1,21 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Try to initialise a DST struct where the lost information is deeply nested.
+// This is an error because it requires an unsized rvalue. This is a problem
+// because it would require stack allocation of an unsized temporary (*g in the
+// test).
+
+pub fn main() {
+    let f: ([isize; 3],) = ([5, 6, 7],);
+    let g: &([isize],) = &f;
+    let h: &(([isize],),) = &(*g,);
+    //~^ ERROR `[isize]: std::marker::Sized` is not satisfied
+}

src/test/run-pass-valgrind/dst-dtor-1.rs

@@ -28,7 +28,8 @@ struct Fat<T: ?Sized> {
 
 pub fn main() {
     {
-        let _x: Box<Fat<Trait>> = Box::<Fat<Foo>>::new(Fat { f: Foo });
+        let _x: Box<(i32, Fat<Trait>)> =
+            Box::<(i32, Fat<Foo>)>::new((42, Fat { f: Foo }));
     }
     unsafe {
         assert!(DROP_RAN);

src/test/run-pass-valgrind/dst-dtor-2.rs

@@ -25,7 +25,8 @@ struct Fat<T: ?Sized> {
 
 pub fn main() {
     {
-        let _x: Box<Fat<[Foo]>> = Box::<Fat<[Foo; 3]>>::new(Fat { f: [Foo, Foo, Foo] });
+        let _x: Box<(Fat<[Foo]>,)> =
+            Box::<(Fat<[Foo; 3]>,)>::new((Fat { f: [Foo, Foo, Foo] },));
     }
     unsafe {
         assert_eq!(DROP_RAN, 3);

src/test/run-pass/dst-irrefutable-bind.rs

@@ -21,4 +21,14 @@ fn main() {
     let slice = &[1,2,3];
     let x = Test(&slice);
     let Test(&_slice) = x;
+
+
+    let x = (10, [1,2,3]);
+    let x : &(i32, [i32]) = &x;
+
+    let & ref _y = x;
+
+    let slice = &[1,2,3];
+    let x = (10, &slice);
+    let (_, &_slice) = x;
 }

src/test/run-pass/dst-raw.rs

@@ -45,6 +45,14 @@ pub fn main() {
     };
     assert_eq!(r, 42);
 
+    // raw DST tuple
+    let p = (A { f: 42 },);
+    let o: *const (Trait,) = &p;
+    let r = unsafe {
+        (&*o).0.foo()
+    };
+    assert_eq!(r, 42);
+
     // raw slice
     let a: *const [_] = &[1, 2, 3];
     unsafe {
@@ -72,6 +80,15 @@ pub fn main() {
         assert_eq!(len, 3);
     }
 
+    // raw DST tuple with slice
+    let c: *const ([_],) = &([1, 2, 3],);
+    unsafe {
+        let b = (&*c).0[0];
+        assert_eq!(b, 1);
+        let len = (&*c).0.len();
+        assert_eq!(len, 3);
+    }
+
     // all of the above with *mut
     let mut x = A { f: 42 };
     let z: *mut Trait = &mut x;
@@ -87,6 +104,13 @@ pub fn main() {
     };
     assert_eq!(r, 42);
 
+    let mut p = (A { f: 42 },);
+    let o: *mut (Trait,) = &mut p;
+    let r = unsafe {
+        (&*o).0.foo()
+    };
+    assert_eq!(r, 42);
+
     let a: *mut [_] = &mut [1, 2, 3];
     unsafe {
         let b = (*a)[2];
@@ -110,4 +134,12 @@ pub fn main() {
         let len = (&*c).f.len();
         assert_eq!(len, 3);
     }
+
+    let c: *mut ([_],) = &mut ([1, 2, 3],);
+    unsafe {
+        let b = (&*c).0[0];
+        assert_eq!(b, 1);
+        let len = (&*c).0.len();
+        assert_eq!(len, 3);
+    }
 }