Implement slicing syntax.

`expr[]`, `expr[expr..]`, `expr[..expr]`,`expr[expr..expr]`

Uses the Slice and SliceMut traits.

Allows ... as well as .. in range patterns.

Author: Nick Cameron

src/libcollections/vec.rs

@@ -20,6 +20,7 @@ use core::default::Default;
 use core::fmt;
 use core::mem;
 use core::num;
+use core::ops;
 use core::ptr;
 use core::raw::Slice as RawSlice;
 use core::uint;
@@ -464,6 +465,47 @@ impl<T> Index<uint,T> for Vec<T> {
     }
 }*/
 
+impl<T> ops::Slice<uint, [T]> for Vec<T> {
+    #[inline]
+    fn as_slice_<'a>(&'a self) -> &'a [T] {
+        self.as_slice()
+    }
+
+    #[inline]
+    fn slice_from_<'a>(&'a self, start: &uint) -> &'a [T] {
+        self.as_slice().slice_from_(start)
+    }
+
+    #[inline]
+    fn slice_to_<'a>(&'a self, end: &uint) -> &'a [T] {
+        self.as_slice().slice_to_(end)
+    }
+    #[inline]
+    fn slice_<'a>(&'a self, start: &uint, end: &uint) -> &'a [T] {
+        self.as_slice().slice_(start, end)
+    }
+}
+
+impl<T> ops::SliceMut<uint, [T]> for Vec<T> {
+    #[inline]
+    fn as_mut_slice_<'a>(&'a mut self) -> &'a mut [T] {
+        self.as_mut_slice()
+    }
+
+    #[inline]
+    fn slice_from_mut_<'a>(&'a mut self, start: &uint) -> &'a mut [T] {
+        self.as_mut_slice().slice_from_mut_(start)
+    }
+
+    #[inline]
+    fn slice_to_mut_<'a>(&'a mut self, end: &uint) -> &'a mut [T] {
+        self.as_mut_slice().slice_to_mut_(end)
+    }
+    #[inline]
+    fn slice_mut_<'a>(&'a mut self, start: &uint, end: &uint) -> &'a mut [T] {
+        self.as_mut_slice().slice_mut_(start, end)
+    }
+}
 impl<T> FromIterator<T> for Vec<T> {
     #[inline]
     fn from_iter<I:Iterator<T>>(mut iterator: I) -> Vec<T> {
@@ -2327,6 +2369,44 @@ mod tests {
         let _ = vec[3];
     }
 
+    // NOTE uncomment after snapshot
+    /*
+    #[test]
+    #[should_fail]
+    fn test_slice_out_of_bounds_1() {
+        let x: Vec<int> = vec![1, 2, 3, 4, 5];
+        x[-1..];
+    }
+
+    #[test]
+    #[should_fail]
+    fn test_slice_out_of_bounds_2() {
+        let x: Vec<int> = vec![1, 2, 3, 4, 5];
+        x[..6];
+    }
+
+    #[test]
+    #[should_fail]
+    fn test_slice_out_of_bounds_3() {
+        let x: Vec<int> = vec![1, 2, 3, 4, 5];
+        x[-1..4];
+    }
+
+    #[test]
+    #[should_fail]
+    fn test_slice_out_of_bounds_4() {
+        let x: Vec<int> = vec![1, 2, 3, 4, 5];
+        x[1..6];
+    }
+
+    #[test]
+    #[should_fail]
+    fn test_slice_out_of_bounds_5() {
+        let x: Vec<int> = vec![1, 2, 3, 4, 5];
+        x[3..2];
+    }
+    */
+
     #[test]
     fn test_swap_remove_empty() {
         let mut vec: Vec<uint> = vec!();

src/libcore/ops.rs

@@ -638,7 +638,7 @@ shr_impl!(uint u8 u16 u32 u64 int i8 i16 i32 i64)
  * ```
  */
 #[lang="index"]
-pub trait Index<Index,Result> {
+pub trait Index<Index, Result> {
     /// The method for the indexing (`Foo[Bar]`) operation
     fn index<'a>(&'a self, index: &Index) -> &'a Result;
 }
@@ -651,7 +651,7 @@ pub trait Index<Index,Result> {
  * # Example
  *
  * A trivial implementation of `IndexMut`. When `Foo[Foo]` happens, it ends up
- * calling `index`, and therefore, `main` prints `Indexing!`.
+ * calling `index_mut`, and therefore, `main` prints `Indexing!`.
  *
  * ```
  * struct Foo;
@@ -669,11 +669,110 @@ pub trait Index<Index,Result> {
  * ```
  */
 #[lang="index_mut"]
-pub trait IndexMut<Index,Result> {
+pub trait IndexMut<Index, Result> {
     /// The method for the indexing (`Foo[Bar]`) operation
     fn index_mut<'a>(&'a mut self, index: &Index) -> &'a mut Result;
 }
 
+/**
+ *
+ * The `Slice` trait is used to specify the functionality of slicing operations
+ * like `arr[from..to]` when used in an immutable context.
+ *
+ * # Example
+ *
+ * A trivial implementation of `Slice`. When `Foo[..Foo]` happens, it ends up
+ * calling `slice_to`, and therefore, `main` prints `Slicing!`.
+ *
+ * ```
+ * struct Foo;
+ *
+ * impl ::core::ops::Slice<Foo, Foo> for Foo {
+ *     fn as_slice_<'a>(&'a self) -> &'a Foo {
+ *         println!("Slicing!");
+ *         self
+ *     }
+ *     fn slice_from_<'a>(&'a self, from: &Foo) -> &'a Foo {
+ *         println!("Slicing!");
+ *         self
+ *     }
+ *     fn slice_to_<'a>(&'a self, to: &Foo) -> &'a Foo {
+ *         println!("Slicing!");
+ *         self
+ *     }
+ *     fn slice_<'a>(&'a self, from: &Foo, to: &Foo) -> &'a Foo {
+ *         println!("Slicing!");
+ *         self
+ *     }
+ * }
+ *
+ * fn main() {
+ *     Foo[..Foo];
+ * }
+ * ```
+ */
+// FIXME(#17273) remove the postscript _s
+#[lang="slice"]
+pub trait Slice<Idx, Sized? Result> for Sized? {
+    /// The method for the slicing operation foo[]
+    fn as_slice_<'a>(&'a self) -> &'a Result;
+    /// The method for the slicing operation foo[from..]
+    fn slice_from_<'a>(&'a self, from: &Idx) -> &'a Result;
+    /// The method for the slicing operation foo[..to]
+    fn slice_to_<'a>(&'a self, to: &Idx) -> &'a Result;
+    /// The method for the slicing operation foo[from..to]
+    fn slice_<'a>(&'a self, from: &Idx, to: &Idx) -> &'a Result;
+}
+
+/**
+ *
+ * The `SliceMut` trait is used to specify the functionality of slicing
+ * operations like `arr[from..to]`, when used in a mutable context.
+ *
+ * # Example
+ *
+ * A trivial implementation of `SliceMut`. When `Foo[Foo..]` happens, it ends up
+ * calling `slice_from_mut`, and therefore, `main` prints `Slicing!`.
+ *
+ * ```
+ * struct Foo;
+ *
+ * impl ::core::ops::SliceMut<Foo, Foo> for Foo {
+ *     fn as_mut_slice_<'a>(&'a mut self) -> &'a mut Foo {
+ *         println!("Slicing!");
+ *         self
+ *     }
+ *     fn slice_from_mut_<'a>(&'a mut self, from: &Foo) -> &'a mut Foo {
+ *         println!("Slicing!");
+ *         self
+ *     }
+ *     fn slice_to_mut_<'a>(&'a mut self, to: &Foo) -> &'a mut Foo {
+ *         println!("Slicing!");
+ *         self
+ *     }
+ *     fn slice_mut_<'a>(&'a mut self, from: &Foo, to: &Foo) -> &'a mut Foo {
+ *         println!("Slicing!");
+ *         self
+ *     }
+ * }
+ *
+ * fn main() {
+ *     Foo[mut Foo..];
+ * }
+ * ```
+ */
+// FIXME(#17273) remove the postscript _s
+#[lang="slice_mut"]
+pub trait SliceMut<Idx, Sized? Result> for Sized? {
+    /// The method for the slicing operation foo[]
+    fn as_mut_slice_<'a>(&'a mut self) -> &'a mut Result;
+    /// The method for the slicing operation foo[from..]
+    fn slice_from_mut_<'a>(&'a mut self, from: &Idx) -> &'a mut Result;
+    /// The method for the slicing operation foo[..to]
+    fn slice_to_mut_<'a>(&'a mut self, to: &Idx) -> &'a mut Result;
+    /// The method for the slicing operation foo[from..to]
+    fn slice_mut_<'a>(&'a mut self, from: &Idx, to: &Idx) -> &'a mut Result;
+}
 /**
  *
  * The `Deref` trait is used to specify the functionality of dereferencing

src/libcore/slice.rs

@@ -42,6 +42,7 @@ use cmp;
 use default::Default;
 use iter::*;
 use num::{CheckedAdd, Saturating, div_rem};
+use ops;
 use option::{None, Option, Some};
 use ptr;
 use ptr::RawPtr;
@@ -475,6 +476,63 @@ impl<'a,T> ImmutableSlice<'a, T> for &'a [T] {
     }
 }
 
+impl<T> ops::Slice<uint, [T]> for [T] {
+    #[inline]
+    fn as_slice_<'a>(&'a self) -> &'a [T] {
+        self
+    }
+
+    #[inline]
+    fn slice_from_<'a>(&'a self, start: &uint) -> &'a [T] {
+        self.slice_(start, &self.len())
+    }
+
+    #[inline]
+    fn slice_to_<'a>(&'a self, end: &uint) -> &'a [T] {
+        self.slice_(&0, end)
+    }
+    #[inline]
+    fn slice_<'a>(&'a self, start: &uint, end: &uint) -> &'a [T] {
+        assert!(*start <= *end);
+        assert!(*end <= self.len());
+        unsafe {
+            transmute(RawSlice {
+                    data: self.as_ptr().offset(*start as int),
+                    len: (*end - *start)
+                })
+        }
+    }
+}
+
+impl<T> ops::SliceMut<uint, [T]> for [T] {
+    #[inline]
+    fn as_mut_slice_<'a>(&'a mut self) -> &'a mut [T] {
+        self
+    }
+
+    #[inline]
+    fn slice_from_mut_<'a>(&'a mut self, start: &uint) -> &'a mut [T] {
+        let len = &self.len();
+        self.slice_mut_(start, len)
+    }
+
+    #[inline]
+    fn slice_to_mut_<'a>(&'a mut self, end: &uint) -> &'a mut [T] {
+        self.slice_mut_(&0, end)
+    }
+    #[inline]
+    fn slice_mut_<'a>(&'a mut self, start: &uint, end: &uint) -> &'a mut [T] {
+        assert!(*start <= *end);
+        assert!(*end <= self.len());
+        unsafe {
+            transmute(RawSlice {
+                    data: self.as_ptr().offset(*start as int),
+                    len: (*end - *start)
+                })
+        }
+    }
+}
+
 /// Extension methods for vectors such that their elements are
 /// mutable.
 #[experimental = "may merge with other traits; may lose region param; needs review"]

src/librustc/middle/cfg/construct.rs

@@ -424,6 +424,13 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 self.call(expr, pred, &**l, Some(&**r).into_iter())
             }
 
+            ast::ExprSlice(ref base, ref start, ref end, _) => {
+                self.call(expr,
+                          pred,
+                          &**base,
+                          start.iter().chain(end.iter()).map(|x| &**x))
+            }
+
             ast::ExprUnary(_, ref e) if self.is_method_call(expr) => {
                 self.call(expr, pred, &**e, None::<ast::Expr>.iter())
             }

src/librustc/middle/expr_use_visitor.rs

@@ -316,7 +316,7 @@ impl<'d,'t,'tcx,TYPER:mc::Typer<'tcx>> ExprUseVisitor<'d,'t,TYPER> {
             ast::ExprPath(..) => { }
 
             ast::ExprUnary(ast::UnDeref, ref base) => {      // *base
-                if !self.walk_overloaded_operator(expr, &**base, None) {
+                if !self.walk_overloaded_operator(expr, &**base, Vec::new()) {
                     self.select_from_expr(&**base);
                 }
             }
@@ -330,12 +330,23 @@ impl<'d,'t,'tcx,TYPER:mc::Typer<'tcx>> ExprUseVisitor<'d,'t,TYPER> {
             }
 
             ast::ExprIndex(ref lhs, ref rhs) => {       // lhs[rhs]
-                if !self.walk_overloaded_operator(expr, &**lhs, Some(&**rhs)) {
+                if !self.walk_overloaded_operator(expr, &**lhs, vec![&**rhs]) {
                     self.select_from_expr(&**lhs);
                     self.consume_expr(&**rhs);
                 }
             }
 
+            ast::ExprSlice(ref base, ref start, ref end, _) => {    // base[start..end]
+                let args = match (start, end) {
+                    (&Some(ref e1), &Some(ref e2)) => vec![&**e1, &**e2],
+                    (&Some(ref e), &None) => vec![&**e],
+                    (&None, &Some(ref e)) => vec![&**e],
+                    (&None, &None) => Vec::new()
+                };
+                let overloaded = self.walk_overloaded_operator(expr, &**base, args);
+                assert!(overloaded);
+            }
+
             ast::ExprCall(ref callee, ref args) => {    // callee(args)
                 self.walk_callee(expr, &**callee);
                 self.consume_exprs(args);
@@ -430,13 +441,13 @@ impl<'d,'t,'tcx,TYPER:mc::Typer<'tcx>> ExprUseVisitor<'d,'t,TYPER> {
             }
 
             ast::ExprUnary(_, ref lhs) => {
-                if !self.walk_overloaded_operator(expr, &**lhs, None) {
+                if !self.walk_overloaded_operator(expr, &**lhs, Vec::new()) {
                     self.consume_expr(&**lhs);
                 }
             }
 
             ast::ExprBinary(_, ref lhs, ref rhs) => {
-                if !self.walk_overloaded_operator(expr, &**lhs, Some(&**rhs)) {
+                if !self.walk_overloaded_operator(expr, &**lhs, vec![&**rhs]) {
                     self.consume_expr(&**lhs);
                     self.consume_expr(&**rhs);
                 }
@@ -774,7 +785,7 @@ impl<'d,'t,'tcx,TYPER:mc::Typer<'tcx>> ExprUseVisitor<'d,'t,TYPER> {
     fn walk_overloaded_operator(&mut self,
                                 expr: &ast::Expr,
                                 receiver: &ast::Expr,
-                                rhs: Option<&ast::Expr>)
+                                rhs: Vec<&ast::Expr>)
                                 -> bool
     {
         if !self.typer.is_method_call(expr.id) {

src/librustc/middle/lang_items.rs

@@ -247,6 +247,8 @@ lets_do_this! {
     ShrTraitLangItem,                "shr",                     shr_trait;
     IndexTraitLangItem,              "index",                   index_trait;
     IndexMutTraitLangItem,           "index_mut",               index_mut_trait;
+    SliceTraitLangItem,              "slice",                   slice_trait;
+    SliceMutTraitLangItem,           "slice_mut",               slice_mut_trait;
 
     UnsafeTypeLangItem,              "unsafe",                  unsafe_type;