06ad52575a
After this commit, we have to use an explicit `discard` in code such as ``` def g (x : Nat) : IO Nat := ... def f (x : Nat) : IO Unit := do discard <| g x -- type error without the `discard` IO.println x ``` Motivation: prevent users from making mistakes such as ``` def f (xs : Array Nat) : IO Unit := do xs.set! 0 1 IO.println xs ``` when they meant to write ``` def f (xs : Array Nat) : IO Unit := do let xs := xs.set! 0 1 IO.println xs ```
99 lines
2.7 KiB
Text
99 lines
2.7 KiB
Text
import Lean
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open Lean
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open Lean.Elab
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open Lean.Elab.Term
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open Lean.Elab.Command
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open Lean.Format
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open Lean.PrettyPrinter
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open Lean.Meta
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def checkM (stx : TermElabM Syntax) (optionsPerPos : OptionsPerPos := {}) : TermElabM Unit := do
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let opts ← getOptions
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let stx ← stx
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let e ← elabTermAndSynthesize stx none <* throwErrorIfErrors
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let stx' ← delab Name.anonymous [] e optionsPerPos
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let f' ← PrettyPrinter.ppTerm stx'
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let s := f'.pretty opts
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IO.println s
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let env ← getEnv
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match Parser.runParserCategory env `term s "<input>" with
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| Except.error e => throwErrorAt stx e
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| Except.ok stx'' => do
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let e' ← elabTermAndSynthesize stx'' none <* throwErrorIfErrors
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unless (← isDefEq e e') do
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throwErrorAt stx (m!"failed to round-trip" ++ line ++ fmt e ++ line ++ fmt e')
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-- set_option trace.PrettyPrinter.parenthesize true
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set_option format.width 20
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-- #eval checkM `(?m) -- fails round-trip
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#eval checkM `(Sort)
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#eval checkM `(Type)
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#eval checkM `(Type 0)
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#eval checkM `(Type 1)
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-- can't add a new universe variable inside a term...
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#eval checkM `(Type _)
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#eval checkM `(Type (_ + 2))
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#eval checkM `(Nat)
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#eval checkM `(List Nat)
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#eval checkM `(id Nat)
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#eval checkM `(id (id (id Nat)))
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section
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set_option pp.explicit true
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#eval checkM `(List Nat)
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#eval checkM `(id Nat)
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end
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section
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set_option pp.universes true
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#eval checkM `(List Nat)
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#eval checkM `(id Nat)
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#eval checkM `(Sum Nat Nat)
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end
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#eval checkM `(id (id Nat)) (Std.RBMap.empty.insert 4 $ KVMap.empty.insert `pp.explicit true)
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-- specify the expected type of `a` in a way that is not erased by the delaborator
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def typeAs.{u} (α : Type u) (a : α) := ()
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#eval checkM `(fun (a : Nat) => a)
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#eval checkM `(fun (a b : Nat) => a)
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#eval checkM `(fun (a : Nat) (b : Bool) => a)
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#eval checkM `(fun {a b : Nat} => a)
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-- implicit lambdas work as long as the expected type is preserved
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#eval checkM `(typeAs ({α : Type} → (a : α) → α) fun a => a)
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section
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set_option pp.explicit true
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#eval checkM `(fun {α : Type} [ToString α] (a : α) => toString a)
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end
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#eval checkM `((α : Type) → α)
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#eval checkM `((α β : Type) → α) -- group
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#eval checkM `((α β : Type) → Type) -- don't group
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#eval checkM `((α : Type) → (a : α) → α)
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#eval checkM `((α : Type) → (a : α) → a = a)
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#eval checkM `({α : Type} → α)
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#eval checkM `({α : Type} → [ToString α] → α)
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-- TODO: hide `ofNat`
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#eval checkM `(0)
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#eval checkM `(1)
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#eval checkM `(42)
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#eval checkM `("hi")
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set_option pp.structure_instance_type true in
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#eval checkM `({ type := Nat, val := 0 : PointedType })
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#eval checkM `((1,2,3))
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#eval checkM `((1,2).fst)
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#eval checkM `(1 < 2 || true)
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#eval checkM `(id (fun a => a) 0)
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#eval checkM `(typeAs Nat (do
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let x ← pure 1
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discard <| pure 2
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let y := 3
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return x + y))
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