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Diffstat (limited to '')
-rw-r--r-- | src/test/ui/mir/mir_assign_eval_order.rs | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/src/test/ui/mir/mir_assign_eval_order.rs b/src/test/ui/mir/mir_assign_eval_order.rs new file mode 100644 index 000000000..799bf7f3a --- /dev/null +++ b/src/test/ui/mir/mir_assign_eval_order.rs @@ -0,0 +1,67 @@ +// Test evaluation order of assignment expressions is right to left. + +// run-pass + +// We would previously not finish evaluating borrow and FRU expressions before +// starting on the LHS + +struct S(i32); + +fn evaluate_reborrow_before_assign() { + let mut x = &1; + let y = &mut &2; + let z = &3; + // There's an implicit reborrow of `x` on the right-hand side of the + // assignment. Note that writing an explicit reborrow would not show this + // bug, as now there would be two reborrows on the right-hand side and at + // least one of them would happen before the left-hand side is evaluated. + *{ x = z; &mut *y } = x; + assert_eq!(*x, 3); + assert_eq!(**y, 1); // y should be assigned the original value of `x`. +} + +fn evaluate_mut_reborrow_before_assign() { + let mut x = &mut 1; + let y = &mut &mut 2; + let z = &mut 3; + *{ x = z; &mut *y } = x; + assert_eq!(*x, 3); + assert_eq!(**y, 1); // y should be assigned the original value of `x`. +} + +// We should evaluate `x[2]` and borrow the value out *before* evaluating the +// LHS and changing its value. +fn evaluate_ref_to_temp_before_assign_slice() { + let mut x = &[S(0), S(1), S(2)][..]; + let y = &mut &S(7); + *{ x = &[S(3), S(4), S(5)]; &mut *y } = &x[2]; + assert_eq!(2, y.0); + assert_eq!(5, x[2].0); +} + +// We should evaluate `x[2]` and copy the value out *before* evaluating the LHS +// and changing its value. +fn evaluate_fru_to_temp_before_assign_slice() { + let mut x = &[S(0), S(1), S(2)][..]; + let y = &mut S(7); + *{ x = &[S(3), S(4), S(5)]; &mut *y } = S { ..x[2] }; + assert_eq!(2, y.0); + assert_eq!(5, x[2].0); +} + +// We should evaluate `*x` and copy the value out *before* evaluating the LHS +// and dropping `x`. +fn evaluate_fru_to_temp_before_assign_box() { + let x = Box::new(S(0)); + let y = &mut S(1); + *{ drop(x); &mut *y } = S { ..*x }; + assert_eq!(0, y.0); +} + +fn main() { + evaluate_reborrow_before_assign(); + evaluate_mut_reborrow_before_assign(); + evaluate_ref_to_temp_before_assign_slice(); + evaluate_fru_to_temp_before_assign_slice(); + evaluate_fru_to_temp_before_assign_box(); +} |