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Diffstat (limited to 'compiler/rustc_middle/src/query/mod.rs')
| -rw-r--r-- | compiler/rustc_middle/src/query/mod.rs | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs index 9ae519dfe7e..3fdb38a433e 100644 --- a/compiler/rustc_middle/src/query/mod.rs +++ b/compiler/rustc_middle/src/query/mod.rs @@ -1448,6 +1448,28 @@ rustc_queries! { cache_on_disk_if { false } } + /// Returns a list of types which (a) have a potentially significant destructor + /// and (b) may be dropped as a result of dropping a value of some type `ty` + /// (in the given environment). + /// + /// The idea of "significant" drop is somewhat informal and is used only for + /// diagnostics and edition migrations. The idea is that a significant drop may have + /// some visible side-effect on execution; freeing memory is NOT considered a side-effect. + /// The rules are as follows: + /// * Type with no explicit drop impl do not have significant drop. + /// * Types with a drop impl are assumed to have significant drop unless they have a `#[rustc_insignificant_dtor]` annotation. + /// + /// Note that insignificant drop is a "shallow" property. A type like `Vec<LockGuard>` does not + /// have significant drop but the type `LockGuard` does, and so if `ty = Vec<LockGuard>` + /// then the return value would be `&[LockGuard]`. + /// *IMPORTANT*: *DO NOT* run this query before promoted MIR body is constructed, + /// because this query partially depends on that query. + /// Otherwise, there is a risk of query cycles. + query list_significant_drop_tys(ty: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> &'tcx ty::List<Ty<'tcx>> { + desc { |tcx| "computing when `{}` has a significant destructor", ty.value } + cache_on_disk_if { false } + } + /// Computes the layout of a type. Note that this implicitly /// executes in "reveal all" mode, and will normalize the input type. query layout_of( |