Improve inspection message for NullableBooleanElvisInspection

Also report as "should" or "can" depending on severity
So #KT-19006 Fixed

idea/src/META-INF/plugin.xml

@@ -2305,7 +2305,7 @@
     />
 
     <localInspection implementationClass="org.jetbrains.kotlin.idea.inspections.NullableBooleanElvisInspection"
-                     displayName="Equality check can be used instead of elvis"
+                     displayName="Equality check can be used instead of elvis for nullable boolean check"
                      groupPath="Kotlin"
                      groupName="Style issues"
                      enabledByDefault="true"

idea/src/org/jetbrains/kotlin/idea/inspections/NullableBooleanElvisInspection.kt

@@ -50,11 +50,13 @@ class NullableBooleanElvisInspection : AbstractKotlinInspection(), CleanupLocalI
                             is KtWhileExpressionBase -> parentIfOrWhile.condition
                             else -> null
                         }
-                        val highlightType =
+                        val (highlightType, verb) = if (condition != null && condition in expression.parentsWithSelf)
-                                if (condition != null && condition in expression.parentsWithSelf) GENERIC_ERROR_OR_WARNING else INFORMATION
+                            GENERIC_ERROR_OR_WARNING to "should"
+                        else
+                            INFORMATION to "can"
 
                         holder.registerProblem(expression,
-                                               "Equality check can be used instead of elvis",
+                                               "Equality check $verb be used instead of elvis for nullable boolean check",
                                                highlightType,
                                                ReplaceWithEqualityCheckFix())
                     }

idea/testData/inspections/nullableBooleanElvis/inspectionData/expected.xml

@@ -4,48 +4,48 @@
         <line>4</line>
         <module>light_idea_test_case</module>
         <entry_point TYPE="file" FQNAME="test.kt"/>
-        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Equality check can be used instead of elvis</problem_class>
+        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Equality check can be used instead of elvis for nullable boolean check</problem_class>
-        <description>Equality check can be used instead of elvis</description>
+        <description>Equality check should be used instead of elvis for nullable boolean check</description>
     </problem>
     <problem>
         <file>test.kt</file>
         <line>7</line>
         <module>light_idea_test_case</module>
         <entry_point TYPE="file" FQNAME="test.kt"/>
-        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Equality check can be used instead of elvis</problem_class>
+        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Equality check can be used instead of elvis for nullable boolean check</problem_class>
-        <description>Equality check can be used instead of elvis</description>
+        <description>Equality check should be used instead of elvis for nullable boolean check</description>
     </problem>
     <problem>
         <file>test.kt</file>
         <line>10</line>
         <module>light_idea_test_case</module>
         <entry_point TYPE="file" FQNAME="test.kt"/>
-        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Equality check can be used instead of elvis</problem_class>
+        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Equality check can be used instead of elvis for nullable boolean check</problem_class>
-        <description>Equality check can be used instead of elvis</description>
+        <description>Equality check should be used instead of elvis for nullable boolean check</description>
     </problem>
     <problem>
         <file>test.kt</file>
         <line>10</line>
         <module>light_idea_test_case</module>
         <entry_point TYPE="file" FQNAME="test.kt"/>
-        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Equality check can be used instead of elvis</problem_class>
+        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Equality check can be used instead of elvis for nullable boolean check</problem_class>
-        <description>Equality check can be used instead of elvis</description>
+        <description>Equality check should be used instead of elvis for nullable boolean check</description>
     </problem>
     <problem>
         <file>test.kt</file>
         <line>13</line>
         <module>light_idea_test_case</module>
         <entry_point TYPE="file" FQNAME="test.kt"/>
-        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Equality check can be used instead of elvis</problem_class>
+        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Equality check can be used instead of elvis for nullable boolean check</problem_class>
-        <description>Equality check can be used instead of elvis</description>
+        <description>Equality check can be used instead of elvis for nullable boolean check</description>
     </problem>
     <problem>
         <file>test.kt</file>
         <line>14</line>
         <module>light_idea_test_case</module>
         <entry_point TYPE="file" FQNAME="test.kt"/>
-        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Equality check can be used instead of elvis</problem_class>
+        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Equality check can be used instead of elvis for nullable boolean check</problem_class>
-        <description>Equality check can be used instead of elvis</description>
+        <description>Equality check can be used instead of elvis for nullable boolean check</description>
     </problem>
 
 </problems>