From c2cb23807507b5c9e46f9a41fb3084993476deb7 Mon Sep 17 00:00:00 2001 From: Ramkumar Ramachandra Date: Thu, 6 Jun 2013 19:09:56 +0530 Subject: [PATCH 1/2] test/compile-fail: clarify bad-for-loop There are two distinct kinds of bad-for-loops to check for with two distinct error messages. The current bad-for-loop.rs does not make this clear, so rewrite it into bad-for-loop{,-2}.rs. The two failing prototypes are: fn quux(_: &fn(&int) -> int) -> bool { true } fn quux(_: &fn(&int) -> bool) -> () { } Note that the second one runs fine in rust-0.6 (the latest release), and only fails with a rust built from `incoming`. Signed-off-by: Ramkumar Ramachandra --- src/test/compile-fail/bad-for-loop-2.rs | 15 +++++++++++++++ src/test/compile-fail/bad-for-loop.rs | 7 ++++--- 2 files changed, 19 insertions(+), 3 deletions(-) create mode 100644 src/test/compile-fail/bad-for-loop-2.rs diff --git a/src/test/compile-fail/bad-for-loop-2.rs b/src/test/compile-fail/bad-for-loop-2.rs new file mode 100644 index 0000000000000..4f90ff5802d7c --- /dev/null +++ b/src/test/compile-fail/bad-for-loop-2.rs @@ -0,0 +1,15 @@ +// Copyright 2012 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 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +fn main() { + fn quux(_: &fn(&int) -> bool) -> () { } + for quux |_| { } //~ ERROR expected `for` closure to return + // `bool`, but found `()` +} diff --git a/src/test/compile-fail/bad-for-loop.rs b/src/test/compile-fail/bad-for-loop.rs index 7ff51eff8eeb6..83616b708f2aa 100644 --- a/src/test/compile-fail/bad-for-loop.rs +++ b/src/test/compile-fail/bad-for-loop.rs @@ -9,7 +9,8 @@ // except according to those terms. fn main() { - fn baz(_x: &fn(y: int) -> int) {} - for baz |_e| { } //~ ERROR A `for` loop iterator should expect a closure that returns `bool` - //~^ ERROR expected `for` closure to return `bool` + fn quux(_: &fn(&int) -> int) -> bool { true } + for quux |_| { } //~ ERROR A `for` loop iterator should expect a + // closure that returns `bool`. This iterator + // expects a closure that returns `int`. } From dd923e3831f93c7ad8f3b872069fdeff31e522c7 Mon Sep 17 00:00:00 2001 From: Ramkumar Ramachandra Date: Thu, 6 Jun 2013 19:23:38 +0530 Subject: [PATCH 2/2] tutorial: fix for-loop example Although in the example function `each` works as expected with rust-0.6 (the latest release), it fails to even compile with `incoming` rust (see test/compile-fail/bad-for-loop-2.rs). Change the function to return a `bool` instead of `()`: this works fine with both versions of rust, and does not misguide potential contributors. Signed-off-by: Ramkumar Ramachandra --- doc/tutorial.md | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/doc/tutorial.md b/doc/tutorial.md index 14a0c6fdcfe27..8caf8704e0589 100644 --- a/doc/tutorial.md +++ b/doc/tutorial.md @@ -1613,18 +1613,19 @@ loop. Like `do`, `for` is a nice syntax for describing control flow with closures. Additionally, within a `for` loop, `break`, `loop`, and `return` work just as they do with `while` and `loop`. -Consider again our `each` function, this time improved to -break early when the iteratee returns `false`: +Consider again our `each` function, this time improved to return +immediately when the iteratee returns `false`: ~~~~ -fn each(v: &[int], op: &fn(v: &int) -> bool) { +fn each(v: &[int], op: &fn(v: &int) -> bool) -> bool { let mut n = 0; while n < v.len() { if !op(&v[n]) { - break; + return false; } n += 1; } + return true; } ~~~~