feat(frontend): Dissect syntax tree

Pantograph/Frontend/InfoTree.lean

@@ -10,7 +10,7 @@ namespace Lean.Elab
 private def elaboratorToString : Name → String
   | .anonymous => ""
   | n => s!"⟨{n}⟩ "
-private def indent (s : String) : String := "\n".intercalate $ s.splitOn "\n" |>.map ("\t" ++ .)
+private def indent (s : String) : String := "\n".intercalate $ s.splitOn "\n" |>.map ("  " ++ .)
 
 /-- The `Syntax` for a `Lean.Elab.Info`, if there is one. -/
 protected def Info.stx? : Info → Option Syntax

Tomograph.lean

@@ -1,5 +1,29 @@
+import Pantograph.Frontend
 
+open Lean
+
+namespace Pantograph
+
+def fail (s : String) : IO Unit := do
+  IO.eprintln s
+
+def dissect (args: List String): IO Unit := do
+  let fileName :: _args := args | fail s!"Must supply a file name"
+  let file ← IO.FS.readFile fileName
+  let (context, state) ← do Frontend.createContextStateFromFile file fileName (env? := .none) {}
+  let frontendM: Elab.Frontend.FrontendM _ :=
+    Frontend.mapCompilationSteps λ step => do
+      for tree in step.trees do
+        IO.println s!"{← tree.toString}"
+  let (_, _) ← frontendM.run context |>.run state
+  return ()
+
+end Pantograph
+
+open Pantograph
 
 def main (args : List String) : IO Unit := do
   let command :: args := args | IO.eprintln "Must supply a command"
-  IO.println s!"{command}"
+  match command with
+  | "dissect" => dissect args
+  | _ => IO.eprintln s!"Unknown command {command}"