feat: Bindings for the `have` tactic

Pantograph.lean

@@ -114,12 +114,15 @@ def execute (command: Protocol.Command): MainM Lean.Json := do
     match state.goalStates.find? args.stateId with
     | .none => return .error $ errorIndex s!"Invalid state index {args.stateId}"
     | .some goalState => do
-      let nextGoalState?: Except _ GoalState ← match args.tactic?, args.expr? with
-        | .some tactic, .none => do
+      let nextGoalState?: Except _ GoalState ← match args.tactic?, args.expr?, args.have? with
+        | .some tactic, .none, .none => do
           pure ( Except.ok (← goalTactic goalState args.goalId tactic))
-        | .none, .some expr => do
-          pure ( Except.ok (← goalTryAssign goalState args.goalId expr))
-        | _, _ => pure (Except.error <| errorI "arguments" "Exactly one of {tactic, expr} must be supplied")
+        | .none, .some expr, .none => do
+          pure ( Except.ok (← goalAssign goalState args.goalId expr))
+        | .none, .none, .some type => do
+          let binderName := args.binderName?.getD ""
+          pure ( Except.ok (← goalHave goalState args.goalId binderName type))
+        | _, _, _ => pure (Except.error <| errorI "arguments" "Exactly one of {tactic, expr, have} must be supplied")
       match nextGoalState? with
       | .error error => return .error error
       | .ok (.success nextGoalState) =>

Pantograph/Goal.lean

@@ -1,3 +1,8 @@
+/-
+Functions for handling metavariables
+
+All the functions starting with `try` resume their inner monadic state.
+-/
 import Pantograph.Protocol
 import Lean
 

Pantograph/Library.lean

@@ -162,10 +162,14 @@ def goalStartExpr (expr: String): Lean.CoreM (Protocol.CR GoalState) :=
 def goalTactic (state: GoalState) (goalId: Nat) (tactic: String): Lean.CoreM TacticResult :=
   runTermElabM <| GoalState.tryTactic state goalId tactic
 
-@[export pantograph_goal_try_assign_m]
-def goalTryAssign (state: GoalState) (goalId: Nat) (expr: String): Lean.CoreM TacticResult :=
+@[export pantograph_goal_assign_m]
+def goalAssign (state: GoalState) (goalId: Nat) (expr: String): Lean.CoreM TacticResult :=
   runTermElabM <| GoalState.tryAssign state goalId expr
 
+@[export pantograph_goal_have_m]
+def goalHave (state: GoalState) (goalId: Nat) (binderName: String) (type: String): Lean.CoreM TacticResult :=
+  runTermElabM <| GoalState.tryHave state goalId binderName type
+
 @[export pantograph_goal_continue]
 def goalContinue (target: GoalState) (branch: GoalState): Except String GoalState :=
   target.continue branch

Pantograph/Protocol.lean

@@ -201,6 +201,11 @@ structure GoalTactic where
   -- One of the fields here must be filled
   tactic?: Option String := .none
   expr?: Option String := .none
+  have?: Option String := .none
+
+  -- In case of the `have` tactic, the new free variable name
+  binderName?: Option String := .none
+
   deriving Lean.FromJson
 structure GoalTacticResult where
   -- The next goal state id. Existence of this field shows success