Avoid errors in Type::with(HeapType) #7551
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Use the standard utility rather than reimplementing type intersection. The new code is simpler, shorter, and properly supports exactness, avoiding an assertion failure in the added test case. The other functional change is that when one of the intersected heap types is bottom and the type GLB is a non-nullable reference to bottom, the result of the intersection is `None` where it was previously a `Cone`.
Previously doing e.g. `type.with(HeapType::none)` would cause an assertion failure if `type` was exact because `.with()` would only replace the heap type and exact references to basic heap types are disallowed. Rather than checking for and avoiding this error in all the callers, simply drop exactness when `.with()` is called with a basic heap type. This is reasonable behavior because the only alternative is never correct. Add a test that hits an assertion failure without this fix. AbstractTypeRefining replaces a defined type with `none` and the type updating utility does not check whether the new heap type is basic before doing the replacement.
kripken
approved these changes
Apr 28, 2025
| @@ -419,7 +419,9 @@ class Type { | |||
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| // Return a new reference type with some part updated to the specified value. | |||
| Type with(HeapType heapType) const { | |||
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Worth a comment about basic types and exactness here I think.
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Previously doing e.g.
type.with(HeapType::none)would cause anassertion failure if
typewas exact because.with()would onlyreplace the heap type and exact references to basic heap types are
disallowed.
Rather than checking for and avoiding this error in all the callers,
simply drop exactness when
.with()is called with a basic heap type.This is reasonable behavior because the only alternative is never
correct.
Add a test that hits an assertion failure without this fix.
AbstractTypeRefining replaces a defined type with
noneand the typeupdating utility does not check whether the new heap type is basic
before doing the replacement.