Turn buildCfg into a method

Signed-off-by: Danila Fedorin <danila.fedorin@gmail.com>

lean/Spa/Language/Graphs.lean

@@ -167,10 +167,10 @@ export GGraph (comp link loop skipto singleton wrap loop_inputs loop_outputs)
 end Graph
 
 open Graph in
-def buildCfg : Stmt → Graph
+def Stmt.cfg : Stmt → Graph
   | .basic bs => singleton [bs]
-  | .andThen s₁ s₂ => buildCfg s₁ ⤳ buildCfg s₂
-  | .ifElse _ s₁ s₂ => buildCfg s₁ ∙ buildCfg s₂
-  | .whileLoop _ s => loop (buildCfg s)
+  | .andThen s₁ s₂ => s₁.cfg ⤳  s₂.cfg
+  | .ifElse _ s₁ s₂ => s₁.cfg ∙ s₂.cfg
+  | .whileLoop _ s => loop s.cfg
 
 end Spa

lean/Spa/Language/Properties.lean

@@ -174,8 +174,8 @@ theorem EndToEndTrace.wrap {g : Graph} {ρ₁ ρ₂ : Env}
     (etr : EndToEndTrace g ρ₁ ρ₂) : EndToEndTrace (Graph.wrap g) ρ₁ ρ₂ :=
   (EndToEndTrace.singleton_nil ρ₁).concat (etr.concat (EndToEndTrace.singleton_nil ρ₂))
 
-theorem buildCfg_sufficient {s : Stmt} {ρ₁ ρ₂ : Env}
-    (h : EvalStmt ρ₁ s ρ₂) : EndToEndTrace (buildCfg s) ρ₁ ρ₂ := by
+theorem Stmt.cfg_sufficient {s : Stmt} {ρ₁ ρ₂ : Env}
+    (h : EvalStmt ρ₁ s ρ₂) : EndToEndTrace s.cfg ρ₁ ρ₂ := by
   induction h with
   | basic ρ₁ ρ₂ bs hbs =>
     exact EndToEndTrace.singleton (EvalBasicStmts.cons hbs EvalBasicStmts.nil)