Better handling of if/else and empty blocks

Fix a crash due to empy block.
Empty else blocks are removed.

Fixes https://github.com/laurentlb/Shader_Minifier/issues/3

src/main.fs

@@ -79,13 +79,17 @@ let minify file =
   code
 
 let run files =
+  let fail (exn:exn) s =
+        printfn "%s" s;
+        printfn "%s" exn.StackTrace
+        1
   try
     let codes = Array.map minify files
     CGen.print (Array.zip files codes)
     0
   with
-    | Failure s as exn -> printfn "%s" s; 1 //; printfn "%s" exn.StackTrace
-    | exn -> printfn "Error: %s" exn.Message; 1 //; printfn "%s" exn.StackTrace
+    | Failure s as exn -> fail exn s
+    | exn -> fail exn exn.Message
 
 let printHeader () =
   printfn "Shader Minifier %s (c) Laurent Le Brun 2012" Ast.version

src/rewriter.fs

@@ -176,7 +176,9 @@ let instr = function
       if not Ast.noSequence && canOptimize then
         let li = List.choose (function Expr e -> Some e | _ -> None) b
         match returnExp with
-         | None -> Expr (List.reduce (fun acc x -> FunCall(Var ",", [acc;x])) li)
+         | None ->
+            if li = [] then Block []
+            else Expr (List.reduce (fun acc x -> FunCall(Var ",", [acc;x])) li)
          | Some e ->
            let expr = List.reduce (fun acc x -> FunCall(Var ",", [acc;x])) (li@[e])
            Keyword("return", Some expr)
@@ -188,6 +190,7 @@ let instr = function
   | If(Var "true", e1, e2) -> e1
   | If(Var "false", e1, Some e2) -> e2
   | If(Var "false", e1, None) -> Block []
+  | If(c, b, Some (Block [])) -> If(c, b, None)
   | Verbatim s -> Verbatim (stripSpaces s)
   | e -> e
 

tests/unit/empty_block.frag

@@ -2,5 +2,13 @@ void f() {
   if (1) {
     return 2;
   } else {;}
+
+  if (x) {
+     ;
+  } else {}
+
+  if (y); else;
+
+  more_semicolons;;;
   return 3;
 }