mirror of https://github.com/rust-lang/rust
101 lines
4.2 KiB
Rust
101 lines
4.2 KiB
Rust
// ignore-tidy-linelength
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// Test various things that we do not want to promote.
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#![allow(unconditional_panic)]
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use std::cell::Cell;
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use std::mem::ManuallyDrop;
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// We do not promote mutable references.
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static mut TEST1: Option<&mut [i32]> = Some(&mut [1, 2, 3]); //~ ERROR temporary value dropped while borrowed
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static mut TEST2: &'static mut [i32] = {
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let x = &mut [1,2,3]; //~ ERROR temporary value dropped while borrowed
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x
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};
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// We do not promote fn calls in `fn`, including `const fn`.
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pub const fn promote_cal(b: bool) -> i32 {
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const fn foo() { [()][42] }
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if b {
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let _x: &'static () = &foo(); //~ ERROR temporary value dropped while borrowed
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}
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13
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}
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// We do not promote union field accesses in `fn.
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union U { x: i32, y: i32 }
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pub const fn promote_union() {
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let _x: &'static i32 = &unsafe { U { x: 0 }.x }; //~ ERROR temporary value dropped while borrowed
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}
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// We do not promote union field accesses in `const`, either.
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const TEST_UNION: () = {
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let _x: &'static i32 = &unsafe { U { x: 0 }.x }; //~ ERROR temporary value dropped while borrowed
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};
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// In a `const`, we do not promote things with interior mutability. Not even if we "project it away".
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const TEST_INTERIOR_MUT: () = {
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// The "0." case is already ruled out by not permitting any interior mutability in `const`.
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let _val: &'static _ = &(Cell::new(1), 2).1; //~ ERROR temporary value dropped while borrowed
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};
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// This gets accepted by the "outer scope" rule, not promotion.
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const TEST_DROP_OUTER_SCOPE: &String = &String::new();
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// To demonstrate that, we can rewrite it as follows. If this was promotion it would still work.
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const TEST_DROP_NOT_PROMOTE: &String = {
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let x = &String::new(); //~ ERROR destructor of `String` cannot be evaluated at compile-time
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// The "dropped while borrowed" error seems to be suppressed, but the key point is that this
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// fails to compile.
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x
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};
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// We do not promote function calls in `const` initializers in dead code.
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const fn mk_panic() -> u32 { panic!() }
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const fn mk_false() -> bool { false }
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const Y: () = {
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if mk_false() {
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let _x: &'static u32 = &mk_panic(); //~ ERROR temporary value dropped while borrowed
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}
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};
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fn main() {
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// We must not promote things with interior mutability. Not even if we "project it away".
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let _val: &'static _ = &(Cell::new(1), 2).0; //~ ERROR temporary value dropped while borrowed
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let _val: &'static _ = &(Cell::new(1), 2).1; //~ ERROR temporary value dropped while borrowed
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// No promotion of fallible operations.
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let _val: &'static _ = &(1/0); //~ ERROR temporary value dropped while borrowed
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let _val: &'static _ = &(1/(1-1)); //~ ERROR temporary value dropped while borrowed
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let _val: &'static _ = &((1+1)/(1-1)); //~ ERROR temporary value dropped while borrowed
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let _val: &'static _ = &(i32::MIN/-1); //~ ERROR temporary value dropped while borrowed
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let _val: &'static _ = &(i32::MIN/(0-1)); //~ ERROR temporary value dropped while borrowed
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let _val: &'static _ = &(-128i8/-1); //~ ERROR temporary value dropped while borrowed
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let _val: &'static _ = &(1%0); //~ ERROR temporary value dropped while borrowed
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let _val: &'static _ = &(1%(1-1)); //~ ERROR temporary value dropped while borrowed
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let _val: &'static _ = &([1,2,3][4]+1); //~ ERROR temporary value dropped while borrowed
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// No promotion of temporaries that need to be dropped.
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const TEST_DROP: String = String::new();
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let _val: &'static _ = &TEST_DROP;
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//~^ ERROR temporary value dropped while borrowed
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let _val: &'static _ = &&TEST_DROP;
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//~^ ERROR temporary value dropped while borrowed
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//~| ERROR temporary value dropped while borrowed
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let _val: &'static _ = &(&TEST_DROP,);
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//~^ ERROR temporary value dropped while borrowed
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//~| ERROR temporary value dropped while borrowed
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let _val: &'static _ = &[&TEST_DROP; 1];
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//~^ ERROR temporary value dropped while borrowed
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//~| ERROR temporary value dropped while borrowed
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// Make sure there is no value-based reasoning for unions.
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union UnionWithCell {
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f1: i32,
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f2: ManuallyDrop<Cell<i32>>,
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}
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let x: &'static _ = &UnionWithCell { f1: 0 };
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//~^ ERROR temporary value dropped while borrowed
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}
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