Check evaluation order

Author: forki

src/fsharp/FSharp.Compiler.Unittests/SeqFusion.fs

@@ -31,12 +31,12 @@ type SeqFusionTestsModule() =
     member this.FusisonOfTwoMapsKeepsSideEffectOrder() =
         let list = List<string>()
         let data = ["hello"; "world"; "!"]
-        let result = Seq.map (fun x -> x * 3) (Seq.map (fun y -> list.Add y; y.Length) data)
+        let result = Seq.map (fun x -> list.Add(x.ToString()); x * 3) (Seq.map (fun y -> list.Add y; y.Length) data)
 
         // seq is not evaluated yet
         Assert.areEqual 0 list.Count
 
         // evaluate it
         Assert.areEqual [15; 15; 3] (Seq.toList result)
 
-        Assert.areEqual data (Seq.toList list)
+        Assert.areEqual  ["hello"; "5"; "world"; "5"; "!"; "1"] (Seq.toList list)

src/fsharp/Optimizer.fs

@@ -2619,9 +2619,9 @@ and OptimizeApplication cenv env (f0,f0ty,tyargs,args,m) =
     | _ -> 
         match expr' with
         // Rewrite Seq.map f (Seq.map g) xs into Seq.map (fun x -> f(g x)) xs
-        | Expr.App(Expr.Val(valRef,_,_) as outerSeqMap,ttype1,[_;t12],
+        | Expr.App(Expr.Val(valRef,_,_) as outerSeqMap,ttype1,[_;fOutType],
                     [(Expr.Lambda(_,None,None,_,_,m1,fRetType) as f)
-                     Expr.App(Expr.Val(valRef2,_,_),_,[t21;_],
+                     Expr.App(Expr.Val(valRef2,_,_),_,[gInType;_],
                                 [Expr.Lambda(_,None,None,gVals,g,_,gRetType)
                                  rest],_)],m2) when
             valRefEq cenv.g valRef cenv.g.seq_map_vref &&
@@ -2630,7 +2630,7 @@ and OptimizeApplication cenv env (f0,f0ty,tyargs,args,m) =
             let newApp = Expr.App(f,TType_fun(gRetType, fRetType),[],[g],m2)
 
             let reduced =
-               Expr.App(outerSeqMap,ttype1,[t21;t12],
+               Expr.App(outerSeqMap,ttype1,[gInType;fOutType],
                          [Expr.Lambda (newUnique(), None, None, gVals, newApp, m1, gRetType)
                           rest],m2)