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Better error on attempt to rebind identifier for static constant. #9683

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Better error on attempt to rebind identifier for static constant. #9683

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a5f13b2
Better error on attempt to rebind identifier for static constant.
pnkfelix Oct 2, 2013
1567e1f
added a test case.
pnkfelix Oct 2, 2013
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8 changes: 5 additions & 3 deletions src/librustc/middle/resolve.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4336,9 +4336,11 @@ impl Resolver {
self.record_def(pattern.id, def);
}
FoundConst(_) => {
self.resolve_error(pattern.span,
"only refutable patterns \
allowed here");
let msg = format!("only irrefutable patterns \
allowed here; `{}` is a static \
constant",
interner_get(renamed));
self.resolve_error(pattern.span, msg);
}
BareIdentifierPatternUnresolved => {
debug2!("(resolving pattern) binding `{}`",
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20 changes: 20 additions & 0 deletions src/test/compile-fail/refutable-static-in-binding-position.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,20 @@
// Copyright 2012-2013 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.

use b = m::a;

mod m {
pub static a : int = 4;
}

fn main() {
let b = 4; //~ERROR only irrefutable patterns allowed here
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Isn't this basically testing what the behavior already was? It'd be nice to have the 'static constant' message also asserted here.

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Well, I did fix the message to say "irrefutable" instead of "refutable", so technically, this test would flag the previous behavior as wrong. :)

I can throw in the static constant bit, I guess. I don't know what rhyme or reason is typically followed when deciding how much of the error message to include. (I've been idly trying to figure out if I could actually point the user at the span of the relevant import or definition of the static constant, to make things crystal clear...)

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Oh good point, sorry I missed that! I think that the ability is being added soon as well to have //~ ERROR long message [...] other contents with the discriminant pull request, so you'd be able to omit the middle stuff.

A NOTE would be nice, but probably not necessary, especially if you mention that it's already a static constant.

println!("{}", b);
}