Modify rule S126: report if without else in assignment in scala

rules/S126/scala/rule.adoc

@@ -7,6 +7,8 @@ The requirement for a final ``++else++`` statement is defensive programming.
 
 The ``++else++`` statement should either take appropriate action or contain a suitable comment as to why no action is taken. This is consistent with the requirement to have a final ``++case _++`` clause in a ``++match++``.
 
+In Scala, this rule also applies when an ``++if++`` statement without an ``++else++`` clause appears on the right-hand side of an assignment. Since Scala treats ``++if++`` as an expression that returns a value, omitting the ``++else++`` clause results in the assignment receiving ``++Unit++`` (represented as ``++()++``) when the condition is false, which is typically unintended and can lead to type errors or unexpected behavior.
+
 === Noncompliant code example
 
 [source,scala]
@@ -15,7 +17,13 @@ if (x == 0) {
   doSomething
 } else if (x == 1) {
   doSomethingElse
-} 
+}
+----
+[source,scala]
+----
+val result = if (x == 0) {
+  "zero"
+}  
 ----
 
 === Compliant solution
@@ -31,6 +39,15 @@ if (x == 0) {
 }
 ----
 
+[source,scala]
+----
+val result = if (x == 0) {
+  "zero"
+} else {
+  "not zero"
+}
+----
+
 === Exceptions
 
 When all branches of an ``++if++``-``++else if++`` end with ``++return++``, ``++break++`` or ``++throw++``, the code that comes after the ``++if++`` implicitly behaves as if it was in an ``++else++`` clause. This rule will therefore ignore that case.