f7de0c408f
This PR improves the error message when `initialize` (or `opaque`) fails to find an `Inhabited` or `Nonempty` instance. **Before:** ``` failed to synthesize Inhabited Foo ``` **After:** ``` failed to synthesize 'Inhabited' or 'Nonempty' instance for Foo If this type is defined using the 'structure' or 'inductive' command, you can try adding a 'deriving Nonempty' clause to it. ``` Prompted by https://leanprover.zulipchat.com/#narrow/channel/270676-lean4/topic/initialize.20structure.20with.20IO.2ERef/near/564936030 🤖 Prepared with Claude Code --------- Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
30 lines
805 B
Text
30 lines
805 B
Text
/-!
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# Test for improved error message when `initialize` fails due to missing `Nonempty` instance
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See https://leanprover.zulipchat.com/#narrow/channel/270676-lean4/topic/initialize.20structure.20with.20IO.2ERef/near/564920245
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-/
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structure Foo where
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ref : IO.Ref Nat
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def mkFoo : IO Foo := do
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let ref ← IO.mkRef 0
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return { ref }
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/-- error: failed to synthesize 'Inhabited' or 'Nonempty' instance for
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Foo
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If this type is defined using the 'structure' or 'inductive' command, you can try adding a 'deriving Nonempty' clause to it. -/
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#guard_msgs in
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initialize _foo : Foo ← mkFoo
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-- The fix: adding `deriving Nonempty` makes it work
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structure Bar where
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ref : IO.Ref Nat
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deriving Nonempty
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def mkBar : IO Bar := do
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let ref ← IO.mkRef 0
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return { ref }
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initialize _bar : Bar ← mkBar
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