`replaceEquality`🔗

Definition

Replace an equality in a goal or hypothesis with a transformed expression, using a provided transformation function.

def

replaceEquality (goal : Lean.MVarId) (fvarId : Option Lean.FVarId)
  (transform : Lean.Expr → Lean.MetaM (Lean.Expr × Lean.Expr)) :
  Lean.Elab.Tactic.TacticM Lean.MVarId
replaceEquality (goal : Lean.MVarId)
  (fvarId : Option Lean.FVarId)
  (transform :
    Lean.Expr →
      Lean.MetaM
        (Lean.Expr × Lean.Expr)) :
  Lean.Elab.Tactic.TacticM Lean.MVarId

Code

def replaceEquality (goal : MVarId) (fvarId : Option FVarId)
    (transform : Expr → MetaM (Expr × Expr)) : TacticM MVarId := do
  goal.withContext do
    let expr ← match fvarId with
        | some fid => do
          let decl ← fid.getDecl
          pure decl.type
        | none => goal.getType
    let (lift_expr, eq_proof) ← transform expr
    match fvarId with
    | some fid => do
      let mvarId ← getMainGoal
      let h_proof ← mkEqMP eq_proof (mkFVar fid)
      let userName := (← fid.getDecl).userName
      let mvarId ← mvarId.assert userName lift_expr h_proof
      let mvarId ← mvarId.tryClear fid
      let (_, mvarId) ← mvarId.intro1P
      pure mvarId
    | none => do
      let mvarId ← getMainGoal
      mvarId.replaceTargetEq lift_expr eq_proof

Actions: Source · Open Issue

Meaning last changed in v4.34.0-rc2-1-g439785b (2026-08-23).

Self-contained, with its dependencies inlined and proofs replaced by sorry: download the raw file · open it in the Lean web editor.

Dependency graph

Nothing to draw. Its statement rests on no other declaration in this project, and names nothing from a package left unaudited — so the graph is this declaration alone. That is the answer, not a missing picture.

Audit surface: 0 project declarations, 57 external constants

✓ Proved: no sorry anywhere in its closure

This is the tool's own reading of one build's recorded axioms, and it is not robust against an author who wants it to pass. Checking meant to be relied on should go through Comparator, which replays the proof through the kernel from an export against an explicit list of permitted axioms.

replaceEquality🔗

`replaceEquality`🔗