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This PR adds `deriving noncomputable instance Foo for Bar` syntax so that delta-derived instances can be marked noncomputable. Previously, when the underlying instance was noncomputable, `deriving instance` would fail with an opaque async compilation error. Now: - `deriving noncomputable instance Foo for Bar` marks the generated instance as noncomputable (using `addDecl` + `addNoncomputable` instead of `addAndCompile`) - `deriving instance Foo for Bar` pre-checks for noncomputable dependencies and gives an actionable error with a "Try this:" suggestion pointing to the noncomputable variant - For handler-based deriving (inductives/structures), `noncomputable` sets `isNoncomputable` on the scope The `optDefDeriving` and `optDeriving` trailing parsers are updated with `notSymbol "noncomputable"` to prevent them from stealing the parse of `deriving noncomputable instance ...`. 🤖 Prepared with Claude Code --------- Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
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