Require exact type equality + add tests

+ Rebase fixes

Author: petrochenkov

src/doc/reference.md

@@ -2392,6 +2392,8 @@ The currently implemented features of the reference compiler are:
 
 * - `deprecated` - Allows using the `#[deprecated]` attribute.
 
+* - `type_ascription` - Allows type ascription expressions `expr: Type`.
+
 If a feature is promoted to a language feature, then all existing programs will
 start to receive compilation warnings about `#![feature]` directives which enabled
 the new feature (because the directive is no longer necessary). However, if a

src/librustc_typeck/check/mod.rs

@@ -2671,6 +2671,14 @@ fn check_lit<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
     }
 }
 
+fn check_expr_eq_type<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
+                                expr: &'tcx hir::Expr,
+                                expected: Ty<'tcx>) {
+    check_expr_with_unifier(
+        fcx, expr, ExpectHasType(expected), NoPreference,
+        || demand::eqtype(fcx, expr.span, expected, fcx.expr_ty(expr)));
+}
+
 pub fn check_expr_has_type<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
                                      expr: &'tcx hir::Expr,
                                      expected: Ty<'tcx>) {
@@ -3527,7 +3535,7 @@ fn check_expr_with_unifier<'a, 'tcx, F>(fcx: &FnCtxt<'a, 'tcx>,
       }
       hir::ExprType(ref e, ref t) => {
         let typ = fcx.to_ty(&**t);
-        check_expr_coercable_to_type(fcx, &**e, typ);
+        check_expr_eq_type(fcx, &**e, typ);
         fcx.write_ty(id, typ);
       }
       hir::ExprVec(ref args) => {

src/libsyntax/parse/parser.rs

@@ -2791,7 +2791,8 @@ impl<'a> Parser<'a> {
                 continue
             } else if op == AssocOp::Colon {
                 let rhs = try!(self.parse_ty());
-                lhs = self.mk_expr(lhs.span.lo, rhs.span.hi, ExprType(lhs, rhs));
+                lhs = self.mk_expr(lhs.span.lo, rhs.span.hi,
+                                   ExprType(lhs, rhs), None);
                 continue
             } else if op == AssocOp::DotDot {
                     // If we didn’t have to handle `x..`, it would be pretty easy to generalise

src/libsyntax_ext/asm.rs

@@ -19,7 +19,7 @@ use syntax::codemap::Span;
 use syntax::ext::base;
 use syntax::ext::base::*;
 use syntax::feature_gate;
-use syntax::parse::token::{intern, InternedString};
+use syntax::parse::token::intern;
 use syntax::parse::{self, token};
 use syntax::ptr::P;
 use syntax::ast::AsmDialect;

src/test/compile-fail/coerce-expect-unsized-ascribed.rs

@@ -0,0 +1,42 @@
+// 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.
+
+// A version of coerce-expect-unsized that uses type ascription.
+// Doesn't work so far, but supposed to work eventually
+
+#![feature(box_syntax, type_ascription)]
+
+use std::fmt::Debug;
+
+pub fn main() {
+    let _ = box { [1, 2, 3] }: Box<[i32]>; //~ ERROR mismatched types
+    let _ = box if true { [1, 2, 3] } else { [1, 3, 4] }: Box<[i32]>; //~ ERROR mismatched types
+    let _ = box match true { true => [1, 2, 3], false => [1, 3, 4] }: Box<[i32]>;
+    //~^ ERROR mismatched types
+    let _ = box { |x| (x as u8) }: Box<Fn(i32) -> _>; //~ ERROR mismatched types
+    let _ = box if true { false } else { true }: Box<Debug>; //~ ERROR mismatched types
+    let _ = box match true { true => 'a', false => 'b' }: Box<Debug>; //~ ERROR mismatched types
+
+    let _ = &{ [1, 2, 3] }: &[i32]; //~ ERROR mismatched types
+    let _ = &if true { [1, 2, 3] } else { [1, 3, 4] }: &[i32]; //~ ERROR mismatched types
+    let _ = &match true { true => [1, 2, 3], false => [1, 3, 4] }: &[i32];
+    //~^ ERROR mismatched types
+    let _ = &{ |x| (x as u8) }: &Fn(i32) -> _; //~ ERROR mismatched types
+    let _ = &if true { false } else { true }: &Debug; //~ ERROR mismatched types
+    let _ = &match true { true => 'a', false => 'b' }: &Debug; //~ ERROR mismatched types
+
+    let _ = Box::new([1, 2, 3]): Box<[i32]>; //~ ERROR mismatched types
+    let _ = Box::new(|x| (x as u8)): Box<Fn(i32) -> _>; //~ ERROR mismatched types
+
+    let _ = vec![
+        Box::new(|x| (x as u8)),
+        box |x| (x as i16 as u8),
+    ]: Vec<Box<Fn(i32) -> _>>;
+}

src/test/compile-fail/type-ascription-precedence.rs

@@ -0,0 +1,64 @@
+// Copyright 2015 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.
+
+// Operator precedence of type ascription
+// Type ascription has very high precedence, the same as operator `as`
+
+#![feature(type_ascription)]
+
+use std::ops::*;
+
+struct S;
+struct Z;
+
+impl Add<Z> for S {
+    type Output = S;
+    fn add(self, _rhs: Z) -> S { panic!() }
+}
+impl Mul<Z> for S {
+    type Output = S;
+    fn mul(self, _rhs: Z) -> S { panic!() }
+}
+impl Neg for S {
+    type Output = Z;
+    fn neg(self) -> Z { panic!() }
+}
+impl Deref for S {
+    type Target = Z;
+    fn deref(&self) -> &Z { panic!() }
+}
+
+fn main() {
+    &S: &S; // OK
+    (&S): &S; // OK
+    &(S: &S); //~ ERROR mismatched types
+
+    *S: Z; // OK
+    (*S): Z; // OK
+    *(S: Z); //~ ERROR mismatched types
+    //~^ ERROR type `Z` cannot be dereferenced
+
+    -S: Z; // OK
+    (-S): Z; // OK
+    -(S: Z); //~ ERROR mismatched types
+    //~^ ERROR cannot apply unary operator `-` to type `Z`
+
+    S + Z: Z; // OK
+    S + (Z: Z); // OK
+    (S + Z): Z; //~ ERROR mismatched types
+
+    S * Z: Z; // OK
+    S * (Z: Z); // OK
+    (S * Z): Z; //~ ERROR mismatched types
+
+    S .. S: S; // OK
+    S .. (S: S); // OK
+    (S .. S): S; //~ ERROR mismatched types
+}

src/test/compile-fail/type-ascription-soundness.rs

@@ -0,0 +1,23 @@
+// Copyright 2015 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.
+
+// Type ascription doesn't lead to unsoundness
+
+#![feature(type_ascription)]
+
+fn main() {
+    let arr = &[1u8, 2, 3];
+    let ref x = arr: &[u8]; //~ ERROR mismatched types
+    let ref mut x = arr: &[u8]; //~ ERROR mismatched types
+    match arr: &[u8] { //~ ERROR mismatched types
+        ref x => {}
+    }
+    let _len = (arr: &[u8]).len(); //~ ERROR mismatched types
+}

src/test/run-pass/coerce-expect-unsized-ascribed.rs

@@ -0,0 +1,45 @@
+// Copyright 2015 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.
+
+// Type ascription doesn't lead to unsoundness
+
+#![feature(type_ascription)]
+
+use std::mem;
+
+const C1: u8 = 10: u8;
+const C2: [u8; 1: usize] = [1];
+
+struct S {
+    a: u8
+}
+
+fn main() {
+    assert_eq!(C1.into(): i32, 10);
+    assert_eq!(C2[0], 1);
+
+    let s = S { a: 10: u8 };
+    let arr = &[1u8, 2, 3];
+
+    let mut v = arr.iter().cloned().collect(): Vec<_>;
+    v.push(4);
+    assert_eq!(v, [1, 2, 3, 4]);
+
+    let a = 1: u8;
+    let b = a.into(): u16;
+    assert_eq!(v[a.into(): usize], 2);
+    assert_eq!(mem::size_of_val(&a), 1);
+    assert_eq!(mem::size_of_val(&b), 2);
+    assert_eq!(b, 1: u16);
+
+    let mut v = Vec::new();
+    v: Vec<u8> = vec![1, 2, 3]; // Lvalue type ascription
+    assert_eq!(v, [1u8, 2, 3]);
+}