check if the expr type is unit for match expressions, too.

Author: dawedawe

src/Compiler/Checking/TailCallChecks.fs

@@ -47,8 +47,16 @@ type TailCall =
     static member YesFromVal (g: TcGlobals) (v: Val) = TailCall.Yes(TailCall.IsVoidRet g v)
 
     static member YesFromExpr (g: TcGlobals) (expr: Expr) =
+        let yesFromTType (t: TType) =
+            if isUnitTy g t then
+                TailCall.Yes TailCallReturnType.MustReturnVoid
+            else
+                TailCall.Yes TailCallReturnType.NonVoid
+
         match expr with
         | ValUseAtApp(valRef, _) -> TailCall.Yes(TailCall.IsVoidRet g valRef.Deref)
+        | Expr.Const(constType = constType) -> yesFromTType constType
+        | Expr.Match(exprType = exprType) -> yesFromTType exprType
         | _ -> TailCall.Yes TailCallReturnType.NonVoid
 
     member x.AtExprLambda =