fix non-copyable derived dependency passed as base-class reference (issue #467)#679
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…ssue boost-ext#467) When an action or guard takes Base& but the sm<> ctor receives Derived& (e.g. NiceMock<T>, any type with a deleted copy constructor), the pool init copy-constructor called try_get<Base>() which found nothing in the source pool (which held Derived&) and fell back to missing_ctor_parameter<Base>. missing_ctor_parameter tried to default-construct Base and bind it to Base& — which fails (can't bind a reference to a temporary). Root cause: try_get had no covariant overloads; lookup was exact-type only. Fix: add two new try_get overloads constrained on is_base_of<T,D>: try_get<T>(pool_type<D&>*) -> T& try_get<T>(pool_type<const D&>*) -> const T& Both return the stored D& / const D& value, which implicitly converts to the base-class reference T& / const T&. is_same<T,D> is excluded to prevent ambiguity with the existing exact-match overloads. Regression test: non_copyable_derived_dep_as_base_ref in test/ft/dependencies.cpp — passes derived467 (inherits base467, deleted copy ctor) to sm<c467> whose action takes base467&.
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Fixes #467.
Root cause
When an action takes
Base&but thesm<>constructor receivesDerived&(e.g.NiceMock<T>, or any type with a deleted copy constructor), the pool init copy-constructor calledtry_get<Base>(&source_pool). The source pool heldpool_type<Derived&>, notpool_type<Base&>, so the exact-match overload was not viable. The fallbacktry_get(...)returnedmissing_ctor_parameter<Base>, which tried to default-constructBaseand bind it toBase&— which fails (cannot bind a reference to a temporary).This regression was introduced in v1.1.4 when
missing_ctor_parameterwas added.Fix
Add two covariant
try_getoverloads constrained onis_base_of<T,D> && !is_same<T,D>:Both return the stored
D&/const D&value, which implicitly upcasts toT&/const T&. The!is_same<T,D>constraint prevents ambiguity with the existing exact-match overloads.Test
Added
non_copyable_derived_dep_as_base_reftotest/ft/dependencies.cpp: passesderived467(inheritsbase467, copy ctor deleted) tosm<c467>whose action takesbase467&.