mirror of https://github.com/rust-lang/rust
68 lines
2.1 KiB
Rust
68 lines
2.1 KiB
Rust
// Test evaluation order of assignment expressions is right to left.
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//@ run-pass
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// We would previously not finish evaluating borrow and FRU expressions before
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// starting on the LHS
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struct S(i32);
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fn evaluate_reborrow_before_assign() {
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let mut x = &1;
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let y = &mut &2;
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let z = &3;
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// There's an implicit reborrow of `x` on the right-hand side of the
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// assignment. Note that writing an explicit reborrow would not show this
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// bug, as now there would be two reborrows on the right-hand side and at
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// least one of them would happen before the left-hand side is evaluated.
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*{ x = z; &mut *y } = x;
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assert_eq!(*x, 3);
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assert_eq!(**y, 1); // y should be assigned the original value of `x`.
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}
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fn evaluate_mut_reborrow_before_assign() {
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let mut x = &mut 1;
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let y = &mut &mut 2;
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let z = &mut 3;
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*{ x = z; &mut *y } = x;
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assert_eq!(*x, 3);
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assert_eq!(**y, 1); // y should be assigned the original value of `x`.
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}
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// We should evaluate `x[2]` and borrow the value out *before* evaluating the
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// LHS and changing its value.
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fn evaluate_ref_to_temp_before_assign_slice() {
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let mut x = &[S(0), S(1), S(2)][..];
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let y = &mut &S(7);
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*{ x = &[S(3), S(4), S(5)]; &mut *y } = &x[2];
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assert_eq!(2, y.0);
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assert_eq!(5, x[2].0);
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}
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// We should evaluate `x[2]` and copy the value out *before* evaluating the LHS
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// and changing its value.
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fn evaluate_fru_to_temp_before_assign_slice() {
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let mut x = &[S(0), S(1), S(2)][..];
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let y = &mut S(7);
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*{ x = &[S(3), S(4), S(5)]; &mut *y } = S { ..x[2] };
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assert_eq!(2, y.0);
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assert_eq!(5, x[2].0);
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}
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// We should evaluate `*x` and copy the value out *before* evaluating the LHS
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// and dropping `x`.
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fn evaluate_fru_to_temp_before_assign_box() {
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let x = Box::new(S(0));
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let y = &mut S(1);
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*{ drop(x); &mut *y } = S { ..*x };
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assert_eq!(0, y.0);
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}
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fn main() {
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evaluate_reborrow_before_assign();
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evaluate_mut_reborrow_before_assign();
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evaluate_ref_to_temp_before_assign_slice();
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evaluate_fru_to_temp_before_assign_slice();
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evaluate_fru_to_temp_before_assign_box();
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}
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