add let_intros for better experience with levels about functions

2024-03-15 17:06:43 +01:00
parent 6cdbfbd9cb
commit 9bc0a3de46
6 changed files with 123 additions and 11 deletions
@@ -0,0 +1,65 @@
+import Lean.Elab.Binders
+import Lean.Elab.Tactic.Basic
+import Lean.Meta.Tactic.Intro
+
+/-!
+# `let_intros` Tactic
+
+`let_intros` is a weaker form of `intros` aimed to only introduce `let` statements,
+but not for example `∀`-binders.
+-/
+
+namespace GameServer
+
+open Lean Meta Elab Parser Tactic
+
+/--
+Copied from `Lean.Meta.getIntrosSize`.
+-/
+private partial def getLetIntrosSize : Expr → Nat
+  -- | .forallE _ _ b _ => getLetIntrosSize b + 1
+  | .letE _ _ _ b _  => getLetIntrosSize b + 1
+  | .mdata _ b       => getLetIntrosSize b
+  | e                =>
+    if let some (_, _, _, b) := e.letFun? then
+      getLetIntrosSize b + 1
+    else
+      0
+
+/--
+Copied and from `Lean.MVarId.intros`.
+-/
+def _root_.Lean.MVarId.letIntros (mvarId : MVarId) : MetaM (Array FVarId × MVarId) := do
+  let type ← mvarId.getType
+  let type ← instantiateMVars type
+  let n := getLetIntrosSize type
+  if n == 0 then
+    return (#[], mvarId)
+  else
+    -- `introNP` preserves the binder names
+    mvarId.introNP n
+
+/--
+`let_intros` introduces all `let` statements that are preceeding the proof. Concretely
+it does a subset of what `intros` does.
+
+If names are provided, it will introduce as many `let` statements as there are names.
+-/
+syntax (name := letIntros) "let_intros" : tactic
+-- (ppSpace colGt (ident <|> hole))*
+
+#check letIntros
+
+@[tactic letIntros] def evalLetIntros : Tactic := fun stx => do
+  match stx with
+  | `(tactic| let_intros) => liftMetaTactic fun mvarId => do
+    let (_, mvarId) ← mvarId.letIntros
+    return [mvarId]
+  -- | `(tactic| let_intros $ids*) => do
+  --   let fvars ← liftMetaTacticAux fun mvarId => do
+  --     let (fvars, mvarId) ← mvarId.introN ids.size (ids.map getNameOfIdent').toList
+  --     return (fvars, [mvarId])
+  --   withMainContext do
+  --     for stx in ids, fvar in fvars do
+  --       Term.addLocalVarInfo stx (mkFVar fvar)
+  | _ => throwUnsupportedSyntax