PANIC at Lean.Expr.appFn! in Fin.isValue, in the presence of metadata

[eric-wieser]

Prerequisites

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Description

simp only [Fin.isValue] panics in the presence of expression metadata.
An easy way to construct such metadata is @& borrow notation, but in my non-mwe the metadata presumably came from elsewhere.

Context

Steps to Reproduce

1. Run example : (@& (1 : Fin 2)) = 1 := by simp only [Fin.isValue]

Expected behavior: Succeeds

Actual behavior: Panics

Versions

4.11.0-rc1

Additional Information

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Impact

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