fix dotnet/fsharp#583

Author: dsyme

src/fsharp/PostInferenceChecks.fs

@@ -600,7 +600,8 @@ and CheckExprInContext (cenv:cenv) (env:env) expr (context:ByrefCallContext) =
         let ty = tryMkForallTy tps rty in 
         CheckLambdas None cenv env false topValInfo false expr m ty
 
-    | Expr.TyChoose(_,e1,_)  -> 
+    | Expr.TyChoose(tps,e1,_)  -> 
+        let env = BindTypars cenv.g env tps 
         CheckExpr cenv env e1 
 
     | Expr.Match(_,_,dtree,targets,m,ty) -> 

tests/service/ExprTests.fs

@@ -169,12 +169,12 @@ let testILCall2 = System.Console.WriteLine(176)
 
 // Test recursive values in a module
 let rec recValNeverUsedAtRuntime = recFuncIgnoresFirstArg (fun _ -> recValNeverUsedAtRuntime) 1
-and recFuncIgnoresFirstArg (g:int->int) v = v
+and recFuncIgnoresFirstArg g v = v
 
 let testFun4() = 
     // Test recursive values in expression position
     let rec recValNeverUsedAtRuntime = recFuncIgnoresFirstArg (fun _ -> recValNeverUsedAtRuntime) 1
-    and recFuncIgnoresFirstArg (g:int->int) v = v
+    and recFuncIgnoresFirstArg g v = v
 
     recValNeverUsedAtRuntime