78 lines
2.2 KiB
Rust
78 lines
2.2 KiB
Rust
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// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Check that coercions can unify if-else, match arms and array elements.
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// Try to construct if-else chains, matches and arrays out of given expressions.
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macro_rules! check {
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($last:expr $(, $rest:expr)+) => {
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// Last expression comes first because of whacky ifs and matches.
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let _ = $(if false { $rest })else+ else { $last };
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let _ = match 0 { $(_ if false => $rest,)+ _ => $last };
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let _ = [$($rest,)+ $last];
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}
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}
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// Check all non-uniform cases of 2 and 3 expressions of 2 types.
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macro_rules! check2 {
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($a:expr, $b:expr) => {
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check!($a, $b);
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check!($b, $a);
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check!($a, $a, $b);
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check!($a, $b, $a);
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check!($a, $b, $b);
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check!($b, $a, $a);
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check!($b, $a, $b);
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check!($b, $b, $a);
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}
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}
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// Check all non-uniform cases of 2 and 3 expressions of 3 types.
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macro_rules! check3 {
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($a:expr, $b:expr, $c:expr) => {
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// Delegate to check2 for cases where a type repeats.
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check2!($a, $b);
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check2!($b, $c);
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check2!($a, $c);
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// Check the remaining cases, i.e. permutations of ($a, $b, $c).
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check!($a, $b, $c);
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check!($a, $c, $b);
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check!($b, $a, $c);
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check!($b, $c, $a);
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check!($c, $a, $b);
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check!($c, $b, $a);
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}
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}
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use std::mem::size_of;
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fn foo() {}
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fn bar() {}
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pub fn main() {
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check3!(foo, bar, foo as fn());
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check3!(size_of::<u8>, size_of::<u16>, size_of::<usize> as fn() -> usize);
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let s = String::from("bar");
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check2!("foo", &s);
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let a = [1, 2, 3];
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let v = vec![1, 2, 3];
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check2!(&a[..], &v);
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// Make sure in-array coercion still works.
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let _ = [("a", Default::default()), (Default::default(), "b"), (&s, &s)];
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}
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