Hints(,tests): add conditionless reduction

Author: knocte

src/FSharpLint.Core/fsharplint.json

@@ -411,6 +411,7 @@
             "false <> a ===> a",
             "if a then true else false ===> a",
             "if a then false else true ===> not a",
+            "if x then y else y ===> y",
             "not (not x) ===> x",
 
             "(fst x, snd x) ===> x",

tests/FSharpLint.Core.Tests/Rules/Hints/HintMatcher.fs

@@ -964,3 +964,21 @@ let x y =
         this.SetConfig(["(List.singleton x) @ y ===> x :: y"])
         this.Parse(source)
         Assert.AreEqual(expected, this.ApplyQuickFix source)
+
+    [<Test>]
+    member this.``Result same regardless of condition can remove conditional block``() =
+        let source = """
+if (someCondition a b) then
+    res
+else
+    res
+"""
+
+        let expected = """
+res
+"""
+
+        this.SetConfig(["if x then y else y ===> y"])
+        this.Parse(source)
+        Assert.AreEqual(expected, this.ApplyQuickFix source)
+