FIR: Add operator test

compiler/fir/resolve/testData/resolve/expresssions/access.kt

@@ -11,6 +11,14 @@ class Bar {
     val x = ""
 
     fun Foo.abc() = x
+
+    fun bar(): Bar = this
+
+    operator fun String.plus(bar: Bar): String {
+        return ""
+    }
+
+    fun Foo.check() = abc() + bar()
 }
 
 fun Foo.ext() = x

compiler/fir/resolve/testData/resolve/expresssions/access.txt

@@ -24,6 +24,18 @@ FILE: access.kt
             return@@@abc R|/Foo.x|
         }
 
+        public final function bar(): R|Bar| {
+            return@@@bar this#
+        }
+
+        public final operator function plus R|kotlin/String|.(bar: R|Bar|): R|kotlin/String| {
+            return@@@plus String()
+        }
+
+        public final function check R|Foo|.(): R|kotlin/String| {
+            return@@@check R|/Bar.plus|(R|/Foo.abc|(), R|/Bar.bar|())
+        }
+
     }
     public final function ext R|Foo|.(): R|kotlin/Int| {
         return@@@ext R|/Foo.x|

compiler/fir/resolve/testData/resolve/references/simple.txt

@@ -2,6 +2,6 @@ FILE: simple.kt
     public final function foo(): R|kotlin/Int| {
         return@@@foo Int(1)
     }
-    public final function bar(): <implicit> {
+    public final function bar(): R|kotlin/Int| {
         return@@@bar R|/foo|()
     }