20eea7372f
This PR improves the delta deriving handler, giving it the ability to
process definitions with binders, as well as the ability to recursively
unfold definitions. Furthermore, delta deriving now tries all explicit
non-out-param arguments to a class, and it can handle "mixin" instance
arguments. The `deriving` syntax has been changed to accept general
terms, which makes it possible to derive specific instances with for
example `deriving OfNat _ 1` or `deriving Module R`. The class is
allowed to be a pi type, to add additional hypotheses; here is a Mathlib
example:
```lean
def Sym (α : Type*) (n : ℕ) :=
{ s : Multiset α // Multiset.card s = n }
deriving [DecidableEq α] → DecidableEq _
```
This underscore stands for where `Sym α n` may be inserted, which is
necessary when `→` is used. The `deriving instance` command can refer to
scoped variables when delta deriving as well. Breaking change: the
derived instance's name uses the `instance` command's name generator,
and the new instance is added to the current namespace.
This closes
[mathlib4#380](https://github.com/leanprover-community/mathlib4/issues/380).
35 lines
624 B
Text
35 lines
624 B
Text
def Foo := List Nat
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def test (x : Nat) : Foo :=
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[x, x+1, x+2]
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#eval test 4
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#check fun (x y : Foo) => x == y -- Error
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deriving instance BEq, Repr for Foo
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#eval test 4
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#check fun (x y : Foo) => x == y
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def Boo := List (String × String)
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deriving BEq, Repr, DecidableEq
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def mkBoo (s : String) : Boo :=
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[(s, s)]
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#eval mkBoo "hello"
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#eval mkBoo "hell" == mkBoo "hello"
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#eval mkBoo "hello" == mkBoo "hello"
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#eval mkBoo "hello" = mkBoo "hello"
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def M := ReaderT String (StateT Nat IO)
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deriving Monad, MonadState, MonadReader
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#print instMonadM
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def action : M Unit := do
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modify (· + 1)
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dbg_trace "{← read}"
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