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Richard Smith
b1230218d5
Include the index rather than the name in the fingerprint of a symbolic binding. While both the index and the name contribute to the canonical identity, using either one of them in the fingerprint is sufficient to ensure that distinct entities get different fingerprints. Changing the name of a symbolic binding should ideally not result in fingerprint changes, so exclude the name from the fingerprint when we have an index. Use the canonical type and constraint when fingerprinting an impl, so that uses of names in `name_ref` instructions aren't considered, only the entity the name resolves to, and different ways of spelling the same type have the same fingerprint. This similarly allows compatible changes to be made to impls without changing the fingerprint. Exclude the declaration block when determining the fingerprint of a declaration. The declaration block contains the declarations of parameters of the declaration, which do affect whether two declarations are identical, but not whether they denote the same entity, because it would be invalid to have different declaration blocks for declarations with the same name in the same scope. Therefore changes to the declaration block are compatible, and it's useful for such changes to not affect the fingerprint. This is not easy to test in isolation with our current testing machinery. However, a follow-on PR will change the name of a parameter in the prelude, and with this in place, will not cause any changes to occur elsewhere in the toolchain tests.