4278038940
This PR adds a new, extensible `do` elaborator. Users can opt into the new elaborator by unsetting the option `backward.do.legacy`. New elaborators for the builtin `doElem` syntax category can be registered with attribute `doElem_elab`. For new syntax, additionally a control info handler must be registered with attribute `doElem_control_info` that specifies whether the new syntax `return`s early, `break`s, `continue`s and which `mut` vars it reassigns. Do elaborators have type ``TSyntax `doElem → DoElemCont → DoElabM Expr``, where `DoElabM` is essentially `TermElabM` and the `DoElemCont` represents how the rest of the `do` block is to be elaborated. Consult the docstrings for more details. Breaking Changes: * The syntax for `let pat := rhs | otherwise` and similar now scope over the `doSeq` that follows. Furthermore, `otherwise` and the sequence that follows are now `doSeqIndented` in order not to steal syntax from record syntax. Breaking Changes when opting into the new `do` elaborator by unsetting `backward.do.legacy`: * `do` notation now always requires `Pure`. * `do match` is now always non-dependent. There is `do match (dependent := true)` that expands to a term match as a workaround for some dependent uses.
53 lines
1.2 KiB
Text
53 lines
1.2 KiB
Text
import Lean
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open Lean
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set_option backward.do.legacy false -- only fixed in the new do elaborator
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structure Foo (n : Nat) where
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(l : List Nat)
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(h : n = n)
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def foo (n : Nat) : MetaM Unit := do
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let mut result : Foo n := ⟨[7], rfl⟩
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trace[Meta.Tactic.simp] "{result.l}"
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result := ⟨List.range n, rfl⟩
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trace[Meta.Tactic.simp] "{result.l}"
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match n with
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| _ => trace[Meta.Tactic.simp] "{result.l}"
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set_option trace.Meta.Tactic.simp true
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/--
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trace: [Meta.Tactic.simp] [7]
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[Meta.Tactic.simp] [0, 1, 2, 3, 4]
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[Meta.Tactic.simp] [0, 1, 2, 3, 4]
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-/
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#guard_msgs in
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run_meta do
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foo 5
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def bar (n : Nat) : MetaM (List Nat) := do
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let mut result : Foo n := ⟨[7], rfl⟩
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trace[Meta.Tactic.simp] "{result.l}"
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result := ⟨List.range n, rfl⟩
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trace[Meta.Tactic.simp] "{result.l}"
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have : Foo n := ⟨[7], rfl⟩
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match n with
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| 0 => pure (); result := ⟨[10], rfl⟩
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| _+1 => result := ⟨[6], rfl⟩
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trace[Meta.Tactic.simp] "{result.l}"
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return result.l
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set_option trace.Meta.Tactic.simp true
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/--
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trace: [Meta.Tactic.simp] [7]
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[Meta.Tactic.simp] []
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[Meta.Tactic.simp] [10]
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[Meta.Tactic.simp] [7]
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[Meta.Tactic.simp] [0, 1, 2, 3, 4]
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[Meta.Tactic.simp] [6]
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-/
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#guard_msgs in
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run_meta do
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discard <| bar 0
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discard <| bar 5
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