[all-commits] [llvm/llvm-project] 342e64: [Sema] Fix assertion failure when instantiating re...
Ilya Biryukov via All-commits
all-commits at lists.llvm.org
Thu Jun 23 07:20:59 PDT 2022
Author: Ilya Biryukov <ibiryukov at google.com>
Date: 2022-06-23 (Thu, 23 Jun 2022)
[Sema] Fix assertion failure when instantiating requires expression
The crash is is caused by the double template instantiation.
See the added test. Here is what happens:
- Template arguments for the partial specialization get instantiated.
- This causes instantitation into the corrensponding requires
- `TemplateInsantiator` correctly handles instantiation of parameters
inside `RequiresExprBody` and instantiates the constraint expression
inside the `NestedRequirement`.
- To build the substituted `NestedRequirement`, `TemplateInsantiator`
calls `Sema::BuildNestedRequirement` calls
`CheckConstraintSatisfaction`, which results in another template
instantiation (with empty template arguments). This seem to be an
implementation detail to handle constraint satisfaction and is not
required by the standard.
- The recursive template instantiation tries to find the parameter
inside `RequiresExprBody` and fails with the corresponding assertion.
Note that this only happens as both instantiations happen with the class
partial template specialization set as `Sema.CurContext`, which is
considered a dependent `DeclContext`.
To fix the assertion, avoid doing the recursive template instantiation
and instead evaluate resulting expressions in-place.
Reviewed By: erichkeane
Differential Revision: https://reviews.llvm.org/D127487
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