Rewrite our unconstrained type-param error checking #1030
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…onRef This means TypeBoundPredicate will now be able to inherit all behaviours of normal generics so we do not duplicate the work in handling generics it will also allow us to more easily check for unconstrained type parameters on traits.
The TraitReference wrapper is a class that allows us to work with traits in a query manar. This patch allows us to keep track of the substitution mappings that are defined on the trait. This will always be non-empty since traits always contain an implicit Self type parameter so there is special handling in how we perform monomorphization.
This will allow us to reuse our generic substitions code to manage generic traits and their substitions better. It will unify the handling in one path so we get the same error handling.
This patch removes our old method of checking for unconstrained type
parameters which only worked for the basic cases such as:
impl<T> Foo { }
But checking for unconstrained types is more complex, we need to handle
covariant types such as:
impl<T> *T { }
Or
struct foo<X,Y>(X,Y);
impl<T> foo<&T,*T> {}
This rewrites the algorithm to take advantage of our substition
abstractions and HirIds so we can map the ids of the type-params to be
constrained and look at the trait-references used-arguments when the
generics are applied (or they may be empty) and then do the same for any
used arguments on an algebraic data type.
Fixes #1019
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This is a series of patches that were all required to fix this issue. We
now take advantage of our substitutions abstractions and traits
so that our TypeBoundPredicate's which form the basis of our HRTB code
I think this class is almost akin to rustc existential-trait-references. This now
reuses the same code path to give us the same error checking for generics
as we get with ADT's, functions etc.
With this refactoring in place we can then reuse the abstractions to map the
ID's from the used arguments in the type-bound-predicate, the impl block type
substation mappings and the self type itself.
There are quite a few cases to handle and our testsuite picked up all the regressions
so no behaviour of our existing test-cases have changed now. See each commit for
more detailed information.
Fixes #1019
Addresses #849