Extend CanBeNonNullable rule to check function params

detekt-gradle-plugin/src/main/kotlin/io/gitlab/arturbosch/detekt/invoke/DetektInvoker.kt

@@ -66,8 +66,7 @@ internal class DefaultCliInvoker(
         }
     }
 
-    private fun isBuildFailure(msg: String?) =
-        msg != null && "Build failed with" in msg && "issues" in msg
+    private fun isBuildFailure(msg: String) = "Build failed with" in msg && "issues" in msg
 }
 
 private class DryRunInvoker(private val logger: Logger) : DetektInvoker {

detekt-rules-errorprone/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/bugs/UselessPostfixExpression.kt

@@ -78,24 +78,26 @@ class UselessPostfixExpression(config: Config = Config.empty) : Rule(config) {
             report(postfixExpression)
         }
 
-        getPostfixExpressionChildren(expression.returnedExpression)
-            ?.forEach { report(it) }
+        expression.returnedExpression
+            ?.let(this::getPostfixExpressionChildren)
+            ?.forEach(this::report)
     }
 
     override fun visitBinaryExpression(expression: KtBinaryExpression) {
         val postfixExpression = expression.right?.asPostFixExpression()
         val leftIdentifierText = expression.left?.text
-        checkPostfixExpression(postfixExpression, leftIdentifierText)
-        getPostfixExpressionChildren(expression.right)
+        postfixExpression?.let { checkPostfixExpression(it, leftIdentifierText) }
+        expression.right
+            ?.let(this::getPostfixExpressionChildren)
             ?.forEach { checkPostfixExpression(it, leftIdentifierText) }
     }
 
     private fun KtExpression.asPostFixExpression() = if (this is KtPostfixExpression &&
         (operationToken === PLUSPLUS || operationToken === MINUSMINUS)
     ) this else null
 
-    private fun checkPostfixExpression(postfixExpression: KtPostfixExpression?, leftIdentifierText: String?) {
-        if (postfixExpression != null && leftIdentifierText == postfixExpression.firstChild?.text) {
+    private fun checkPostfixExpression(postfixExpression: KtPostfixExpression, leftIdentifierText: String?) {
+        if (leftIdentifierText == postfixExpression.firstChild?.text) {
             report(postfixExpression)
         }
     }
@@ -118,7 +120,7 @@ class UselessPostfixExpression(config: Config = Config.empty) : Rule(config) {
         )
     }
 
-    private fun getPostfixExpressionChildren(expression: KtExpression?) =
-        expression?.getChildrenOfType<KtPostfixExpression>()
-            ?.filter { it.operationToken === PLUSPLUS || it.operationToken === MINUSMINUS }
+    private fun getPostfixExpressionChildren(expression: KtExpression) =
+        expression.getChildrenOfType<KtPostfixExpression>()
+            .filter { it.operationToken === PLUSPLUS || it.operationToken === MINUSMINUS }
 }

detekt-rules-performance/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/performance/ArrayPrimitive.kt

@@ -65,15 +65,14 @@ class ArrayPrimitive(config: Config = Config.empty) : Rule(config) {
     override fun visitNamedDeclaration(declaration: KtNamedDeclaration) {
         super.visitNamedDeclaration(declaration)
         if (declaration is KtCallableDeclaration) {
-            reportArrayPrimitives(declaration.typeReference)
-            reportArrayPrimitives(declaration.receiverTypeReference)
+            declaration.typeReference?.let(this::reportArrayPrimitives)
+            declaration.receiverTypeReference?.let(this::reportArrayPrimitives)
         }
     }
 
-    private fun reportArrayPrimitives(typeReference: KtTypeReference?) {
-        typeReference
-            ?.collectDescendantsOfType<KtTypeReference> { isArrayPrimitive(it) }
-            ?.forEach { report(CodeSmell(issue, Entity.from(it), issue.description)) }
+    private fun reportArrayPrimitives(typeReference: KtTypeReference) {
+        typeReference.collectDescendantsOfType<KtTypeReference> { isArrayPrimitive(it) }
+            .forEach { report(CodeSmell(issue, Entity.from(it), issue.description)) }
     }
 
     private fun isArrayPrimitive(descriptor: CallableDescriptor): Boolean {