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Test exploring the interactions between all of the different kinds of method collisions I could imagine.

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The different impls are all guarded by cfg-flags, and the revisions could be
used to cover the full power-set of combinations.

(I only included 20 of the possible 32 cases here; the null-set is not
interesting, and the remaining 11 all yielded ambiguous method resolution errors
which did not mix well with this testing strategy; I'm not trying to check UI
for the resolution diagnostics; I'm trying to create checkpoint of current
resolution semantics when compilation succeeds.)
This commit is contained in:
Felix S. Klock II 2021-01-23 00:54:19 -05:00
parent ff4665f45f
commit 532332fa8f
1 changed files with 190 additions and 0 deletions
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src/test/ui/methods/method-lookup-order.rs Normal file
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// ignore-tidy-linelength
// run-pass
// There are five cfg's below. I explored the set of all non-empty combinations
// of the below five cfg's, which is 2^5 - 1 = 31 combinations.
//
// Of the 31, 11 resulted in ambiguous method resolutions; while it may be good
// to have a test for all of the eleven variations of that error, I am not sure
// this particular test is the best way to encode it. So they are skipped in
// this revisions list (but not in the expansion mapping the binary encoding to
// the corresponding cfg flags).
//
// Notable, here are the cases that will be incompatible if something does not override them first:
// {bar_for_foo, valbar_for_et_foo}: these are higher precedent than the `&mut self` method on `Foo`, and so no case matching bx1x1x is included.
// {mutbar_for_foo, valbar_for_etmut_foo} (which are lower precedent than the inherent `&mut self` method on `Foo`; e.g. b10101 *is* included.
// revisions: b00001 b00010 b00011 b00100 b00101 b00110 b00111 b01000 b01001 b01100 b01101 b10000 b10001 b10010 b10011 b10101 b10111 b11000 b11001 b11101
//[b00001]compile-flags: --cfg inherent_mut
//[b00010]compile-flags: --cfg bar_for_foo
//[b00011]compile-flags: --cfg inherent_mut --cfg bar_for_foo
//[b00100]compile-flags: --cfg mutbar_for_foo
//[b00101]compile-flags: --cfg inherent_mut --cfg mutbar_for_foo
//[b00110]compile-flags: --cfg bar_for_foo --cfg mutbar_for_foo
//[b00111]compile-flags: --cfg inherent_mut --cfg bar_for_foo --cfg mutbar_for_foo
//[b01000]compile-flags: --cfg valbar_for_et_foo
//[b01001]compile-flags: --cfg inherent_mut --cfg valbar_for_et_foo
//[b01010]compile-flags: --cfg bar_for_foo --cfg valbar_for_et_foo
//[b01011]compile-flags: --cfg inherent_mut --cfg bar_for_foo --cfg valbar_for_et_foo
//[b01100]compile-flags: --cfg mutbar_for_foo --cfg valbar_for_et_foo
//[b01101]compile-flags: --cfg inherent_mut --cfg mutbar_for_foo --cfg valbar_for_et_foo
//[b01110]compile-flags: --cfg bar_for_foo --cfg mutbar_for_foo --cfg valbar_for_et_foo
//[b01111]compile-flags: --cfg inherent_mut --cfg bar_for_foo --cfg mutbar_for_foo --cfg valbar_for_et_foo
//[b10000]compile-flags: --cfg valbar_for_etmut_foo
//[b10001]compile-flags: --cfg inherent_mut --cfg valbar_for_etmut_foo
//[b10010]compile-flags: --cfg bar_for_foo --cfg valbar_for_etmut_foo
//[b10011]compile-flags: --cfg inherent_mut --cfg bar_for_foo --cfg valbar_for_etmut_foo
//[b10100]compile-flags: --cfg mutbar_for_foo --cfg valbar_for_etmut_foo
//[b10101]compile-flags: --cfg inherent_mut --cfg mutbar_for_foo --cfg valbar_for_etmut_foo
//[b10110]compile-flags: --cfg bar_for_foo --cfg mutbar_for_foo --cfg valbar_for_etmut_foo
//[b10111]compile-flags: --cfg inherent_mut --cfg bar_for_foo --cfg mutbar_for_foo --cfg valbar_for_etmut_foo
//[b11000]compile-flags: --cfg valbar_for_et_foo --cfg valbar_for_etmut_foo
//[b11001]compile-flags: --cfg inherent_mut --cfg valbar_for_et_foo --cfg valbar_for_etmut_foo
//[b11010]compile-flags: --cfg bar_for_foo --cfg valbar_for_et_foo --cfg valbar_for_etmut_foo
//[b11011]compile-flags: --cfg inherent_mut --cfg bar_for_foo --cfg valbar_for_et_foo --cfg valbar_for_etmut_foo
//[b11100]compile-flags: --cfg mutbar_for_foo --cfg valbar_for_et_foo --cfg valbar_for_etmut_foo
//[b11101]compile-flags: --cfg inherent_mut --cfg mutbar_for_foo --cfg valbar_for_et_foo --cfg valbar_for_etmut_foo
//[b11110]compile-flags: --cfg bar_for_foo --cfg mutbar_for_foo --cfg valbar_for_et_foo --cfg valbar_for_etmut_foo
//[b11111]compile-flags: --cfg inherent_mut --cfg bar_for_foo --cfg mutbar_for_foo --cfg valbar_for_et_foo --cfg valbar_for_etmut_foo
struct Foo {}
type S = &'static str;
trait Bar {
fn bar(&self, _: &str) -> S;
}
trait MutBar {
fn bar(&mut self, _: &str) -> S;
}
trait ValBar {
fn bar(self, _: &str) -> S;
}
#[cfg(inherent_mut)]
impl Foo {
fn bar(&mut self, _: &str) -> S {
"In struct impl!"
}
}
#[cfg(bar_for_foo)]
impl Bar for Foo {
fn bar(&self, _: &str) -> S {
"In trait &self impl!"
}
}
#[cfg(mutbar_for_foo)]
impl MutBar for Foo {
fn bar(&mut self, _: &str) -> S {
"In trait &mut self impl!"
}
}
#[cfg(valbar_for_et_foo)]
impl ValBar for &Foo {
fn bar(self, _: &str) -> S {
"In trait self impl for &Foo!"
}
}
#[cfg(valbar_for_etmut_foo)]
impl ValBar for &mut Foo {
fn bar(self, _: &str) -> S {
"In trait self impl for &mut Foo!"
}
}
fn main() {
#![allow(unused_mut)] // some of the impls above will want it.
#![allow(unreachable_patterns)] // the cfg-coding pattern below generates unreachable patterns.
{
macro_rules! all_variants_on_value {
($e:expr) => {
match $e {
#[cfg(bar_for_foo)]
x => assert_eq!(x, "In trait &self impl!"),
#[cfg(valbar_for_et_foo)]
x => assert_eq!(x, "In trait self impl for &Foo!"),
#[cfg(inherent_mut)]
x => assert_eq!(x, "In struct impl!"),
#[cfg(mutbar_for_foo)]
x => assert_eq!(x, "In trait &mut self impl!"),
#[cfg(valbar_for_etmut_foo)]
x => assert_eq!(x, "In trait self impl for &mut Foo!"),
}
}
}
let mut f = Foo {};
all_variants_on_value!(f.bar("f.bar"));
let f_mr = &mut Foo {};
all_variants_on_value!((*f_mr).bar("(*f_mr).bar"));
}
// This is sort of interesting: `&mut Foo` ends up with a significantly
// different resolution order than what was devised above. Presumably this
// is because we can get to a `&self` method by first a deref of the given
// `&mut Foo` and then an autoref, and that is a longer path than a mere
// auto-ref of a `Foo`.
{
let f_mr = &mut Foo {};
match f_mr.bar("f_mr.bar") {
#[cfg(inherent_mut)]
x => assert_eq!(x, "In struct impl!"),
#[cfg(valbar_for_etmut_foo)]
x => assert_eq!(x, "In trait self impl for &mut Foo!"),
#[cfg(mutbar_for_foo)]
x => assert_eq!(x, "In trait &mut self impl!"),
#[cfg(valbar_for_et_foo)]
x => assert_eq!(x, "In trait self impl for &Foo!"),
#[cfg(bar_for_foo)]
x => assert_eq!(x, "In trait &self impl!"),
}
}
// Note that this isn't actually testing a resolution order; if both of these are
// enabled, it yields an ambiguous method resolution error. The test tries to embed
// that fact by testing *both* orders (and so the only way that can be right is if
// they are not actually compatible).
#[cfg(any(bar_for_foo, valbar_for_et_foo))]
{
let f_r = &Foo {};
match f_r.bar("f_r.bar") {
#[cfg(bar_for_foo)]
x => assert_eq!(x, "In trait &self impl!"),
#[cfg(valbar_for_et_foo)]
x => assert_eq!(x, "In trait self impl for &Foo!"),
}
match f_r.bar("f_r.bar") {
#[cfg(valbar_for_et_foo)]
x => assert_eq!(x, "In trait self impl for &Foo!"),
#[cfg(bar_for_foo)]
x => assert_eq!(x, "In trait &self impl!"),
}
}
}