7150a0d538
Closes #3146 Reduction doesn't trigger correctly on the bodies of `let`-expressions in `StructInst`, leading some meta-variables to linger in the terms of some fields. Because of this, default fields may try multiple times (and fail) to be generated, leading to an unexpected error. The solution implemented here is to modify the values of the introduced variables in the local context so as to reduce them correctly.
13 lines
411 B
Text
13 lines
411 B
Text
/-
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Verifies that `let`-bodies are reduced accordingly when trying to construct default fields.
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Fixes `#3146`
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-/
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def Product (m₁ : Type → Type) (m₂ : Type → Type) (α : Type) := m₁ α × m₂ α
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instance [Monad m₁] [Monad m₂] : Monad (Product m₁ m₂) where
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pure x := (pure x, pure x)
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bind o f :=
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let y₁ := do f (← o.1) |>.1
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let y₂ := do f (← o.2) |>.2
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(y₁, y₂)
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