chore: replace partially redundant calls to FnBody.split with .body (#9568)

src/Lean/Compiler/IR/Borrow.lean

@@ -78,8 +78,7 @@ partial def visitFnBody (fnid : FunId) : FnBody → StateM ParamMap Unit
   | FnBody.case _ _ _ alts => alts.forM fun alt => visitFnBody fnid alt.body
   | e => do
     unless e.isTerminal do
-      let (_, b) := e.split
-      visitFnBody fnid b
+      visitFnBody fnid e.body
 
 def visitDecls (env : Environment) (decls : Array Decl) : StateM ParamMap Unit :=
   decls.forM fun decl => match decl with

src/Lean/Compiler/IR/ResetReuse.lean

@@ -216,8 +216,7 @@ partial def collectResets (e : FnBody) : N Unit := do
   | .jdecl _ _ v b => collectResets v; collectResets b
   | .vdecl _ _ (.reset _ x) b => modify fun s => s.insert x; collectResets b
   | e => unless e.isTerminal do
-    let (_, b) := e.split
-    collectResets b
+    collectResets e.body
 
 end ResetReuse
 open ResetReuse

src/Lean/Compiler/IR/Sorry.lean

@@ -45,8 +45,7 @@ partial def visitFnBody (b : FnBody) : ExceptT Name M Unit := do
   | .case _ _ _ alts => alts.forM fun alt => visitFnBody alt.body
   | _ =>
     unless b.isTerminal do
-      let (_, b) := b.split
-      visitFnBody b
+      visitFnBody b.body
 
 def visitDecl (d : Decl) : M Unit := do
   match d with