[PATCH] D62131: [ASTImporter] Remove NonEquivalentDecls from ASTImporter

[Gabor Marton via Phabricator via cfe-commits]

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In D62131#1639168 <https://reviews.llvm.org/D62131#1639168>, @balazske wrote:

> Example about how to get wrong things into `NonEquivalentDecls`:
>  We want to compare `class C` for structural equivalence in the following codes:
>
>   class A {}; class B {int i;}; void x(A *); void y(A *); class C { friend void x(A *); friend void y(A *); };
>
>
> and
>
>   class A {}; class B {int i;}; void x(A *); void y(B *); class C { friend void x(A *); friend void y(B *); };
>
>
> The result is false for `C` but the `NonEquivalentDecls` will contain after the compare a `void x(A*)`<->`void x(A*)` pair.
>
> The reason is that during the check we encounter first a `A`<->`B` pair (iterating over the friends and friend functions, first `y` is encountered and a check for `A` and `B` follows). The `B` is recorded as "tentative equivalence" to `A`. Then we try to check `A` to `A` (during check of `x`) but because there is a "tentative equivalence" with `B` from `A` the check returns false (not equivalent). This false result is recorded as a (incorrect) non-equivalence of the two `x` functions.
>  I want to replace the `DeclsToCheck` and `TentativeEquivalences` with a set of `Decl` pairs (like the NonEquivalentDecls) so it will be possible to record the same **from** Decl with multiple **to** values. (Is there a reason for why there is a `NonEquivalentDecls` cache but not a `EquivalentDecls` or simply a cache for result values?)


Yes, this is indeed a problem. But it is independent from the original problem this patch intends to solve.


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https://reviews.llvm.org/D62131