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Previously a short circuiting && chain would drop the first element after all the other elements, and otherwise follow evaluation order, so code like: f(1).g() && f(2).g() && f(3).g() && f(4).g() would drop the temporaries in the order 2,3,4,1. This made && and || non-associative regarding drop order, so adding ()'s to the expression would change drop order: f(1).g() && (f(2).g() && f(3).g()) && f(4).g() for example would drop in the order 3,2,4,1. As, except for the bool result, there is no data returned by the sub-expressions of the short circuiting binops, we can safely discard of any temporaries created by the sub-expr. Previously, code was already putting the rhs's into terminating scopes, but missed it for the lhs's. This commit addresses this "twist". In the expression, we now also put the lhs into a terminating scope. The drop order for the above expressions is 1,2,3,4 now. |
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| Cargo.toml | ||
| README.md | ||
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.