Remove do ... while loops from the tests and docs.

Author: paulstansifer

doc/rust.md

@@ -1991,28 +1991,19 @@ way.
 
 *TODO*.
 
-### While expressions
+### While loops
 
 ~~~~~~~~{.ebnf .gram}
 while_expr : "while" expr '{' block '}'
            | "do" '{' block '}' "while" expr ;
 ~~~~~~~~
 
-A `while` expression is a loop construct. A `while` loop may be either a
-simple `while` or a `do`-`while` loop.
+A `while` loop begins by evaluating the boolean loop conditional expression.
+If the loop conditional expression evaluates to `true`, the loop body block
+executes and control returns to the loop conditional expression. If the loop
+conditional expression evaluates to `false`, the `while` expression completes.
 
-In the case of a simple `while`, the loop begins by evaluating the boolean
-loop conditional expression. If the loop conditional expression evaluates to
-`true`, the loop body block executes and control returns to the loop
-conditional expression. If the loop conditional expression evaluates to
-`false`, the `while` expression completes.
-
-In the case of a `do`-`while`, the loop begins with an execution of the loop
-body. After the loop body executes, it evaluates the loop conditional
-expression. If it evaluates to `true`, control returns to the beginning of the
-loop body. If it evaluates to `false`, control exits the loop.
-
-An example of a simple `while` expression:
+An example:
 
 ~~~~
 # let mut i = 0;
@@ -2024,18 +2015,6 @@ while i < 10 {
 }
 ~~~~
 
-An example of a `do`-`while` expression:
-
-~~~~
-# let mut i = 0;
-# let println = io::println;
-
-do {
-    println("hello\n");
-    i = i + 1;
-} while i < 10;
-~~~~
-
 ### Infinite loops
 
 A `loop` expression denotes an infinite loop:

doc/tutorial.md

@@ -667,6 +667,15 @@ a specific value, are not allowed.
 keyword `break` can be used to abort the loop, and `cont` can be used
 to abort the current iteration and continue with the next.
 
+~~~~
+let mut cake_amount = 8;
+while cake_amount > 0 {
+    cake_amount -= 1;
+}
+~~~~
+
+`loop` is the preferred way of writing `while true`:
+
 ~~~~
 let mut x = 5;
 while true {
@@ -679,17 +688,6 @@ while true {
 This code prints out a weird sequence of numbers and stops as soon as
 it finds one that can be divided by five.
 
-There's also `while`'s ugly cousin, `do`/`while`, which does not check
-its condition on the first iteration, using traditional syntax:
-
-~~~~
-# fn eat_cake() {}
-# fn any_cake_left() -> bool { false }
-do {
-    eat_cake();
-} while any_cake_left();
-~~~~
-
 For more involved iteration, such as going over the elements of a
 collection, Rust uses higher-order functions. We'll come back to those
 in a moment.
@@ -2496,12 +2494,12 @@ Here is the function which implements the child task:
 fn stringifier(from_parent: comm::port<uint>,
                to_parent: comm::chan<str>) {
     let mut value: uint;
-    do {
+    loop {
         value = comm::recv(from_parent);
         comm::send(to_parent, uint::to_str(value, 10u));
-    } while value != 0u;
+        if value == 0u { break; }
+    }
 }
-
 ~~~~
 
 You can see that the function takes two parameters.  The first is a

src/test/compile-fail/borrowck-lend-flow.rs

@@ -61,24 +61,6 @@ fn while_aliased_mut_cond(cond: bool, cond2: bool) {
     }
 }
 
-fn do_while_aliased_mut(cond: bool) {
-    let mut v = ~3, w = ~4;
-    let mut _x = &mut w;
-    do {
-        borrow(v); //! ERROR loan of mutable local variable as immutable conflicts with prior loan
-        _x = &mut v; //! NOTE prior loan as mutable granted here
-    } while cond;
-}
-
-fn loop_in_block() {
-    let mut v = ~3, w = ~4;
-    let mut _x = &mut w;
-    uint::range(0u, 10u) {|_i|
-        borrow(v); //! ERROR loan of mutable local variable as immutable conflicts with prior loan
-        _x = &mut v; //! NOTE prior loan as mutable granted here
-    }
-}
-
 fn at_most_once_block() {
     fn at_most_once(f: fn()) { f() }
 

src/test/compile-fail/break-uninit.rs

@@ -4,7 +4,7 @@ fn foo() -> int {
     let x: int;
     let i: int;
 
-    do  { i = 0; break; x = 0; } while x != 0
+    loop { i = 0; break; x = 0; }
 
     log(debug, x);
 

src/test/compile-fail/break-uninit2.rs

@@ -4,7 +4,7 @@ fn foo() -> int {
     let x: int;
     let i: int;
 
-    do  { i = 0; break; x = 0; } while 1 != 2
+    while 1 != 2  { i = 0; break; x = 0; }
 
     log(debug, x);
 

src/test/compile-fail/do-while-pred-constraints.rs renamed to src/test/compile-fail/loop-pred-constraints.rs

@@ -1,14 +1,17 @@
+// xfail-test
+// https://github.com/mozilla/rust/issues/2374
 // error-pattern:unsatisfied precondition constraint (for example, even(y
 
+
 fn print_even(y: int) : even(y) { log(debug, y); }
 
 pure fn even(y: int) -> bool { true }
 
 fn main() {
-    let y: int = 42;
+    let mut y = 42;
     check (even(y));
     loop {
         print_even(y);
-        do  { do  { do  { y += 1; } while false } while false } while false
+        loop { y += 1; break; }
     }
 }

src/test/compile-fail/do-while-constraints.rs renamed to src/test/compile-fail/while-constraints.rs

@@ -5,6 +5,6 @@ fn main() {
     let x: int;
     loop {
         log(debug, y);
-        do  { do  { do  { x <- y; } while true } while true } while true
+        while true { while true { while true { x <- y; } } }
     }
 }

src/test/run-fail/do-while-body-fails.rs

@@ -0,0 +1,2 @@
+// error-pattern:quux
+fn main() { let x: int = { while true { fail "quux"; } ; 8 } ; }