Not searching for functions with conventional names.

Reasons:
1. They kind of implement interface.
2. They are too expensive to search.

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

@@ -41,6 +41,8 @@ import org.jetbrains.kotlin.asJava.toLightClass
 import org.jetbrains.kotlin.idea.search.usagesSearch.FunctionUsagesSearchHelper
 import com.intellij.psi.search.PsiSearchHelper
 import com.intellij.psi.search.PsiSearchHelper.SearchCostResult.*
+import org.jetbrains.kotlin.idea.search.usagesSearch.getOperationSymbolsToSearch
+import org.jetbrains.kotlin.idea.search.usagesSearch.INVOKE_OPERATION_NAME
 
 public class UnusedSymbolInspection : AbstractKotlinInspection() {
     private val javaInspection = UnusedDeclarationInspection()
@@ -68,6 +70,7 @@ public class UnusedSymbolInspection : AbstractKotlinInspection() {
 
                 if (function.hasModifier(JetTokens.OVERRIDE_KEYWORD)) return
                 if (isEntryPoint(function)) return
+                if (isConventionalName(function)) return
                 if (hasNonTrivialUsages(function)) return
 
                 holder.registerProblem(
@@ -105,6 +108,11 @@ public class UnusedSymbolInspection : AbstractKotlinInspection() {
         return hasTextUsages
     }
 
+    private fun isConventionalName(namedDeclaration: JetNamedDeclaration): Boolean {
+        val name = namedDeclaration.getNameAsName()
+        return name.getOperationSymbolsToSearch().isNotEmpty() || name == INVOKE_OPERATION_NAME
+    }
+
     private fun hasNonTrivialUsages(declaration: JetNamedDeclaration): Boolean {
         val psiSearchHelper = PsiSearchHelper.SERVICE.getInstance(declaration.getProject())
 

idea/testData/inspections/unusedSymbol/function/conventionalNames.kt

@@ -0,0 +1,34 @@
+// all these are unused, but have conventional names, so they won't be marked as unused
+
+fun inc() {
+}
+
+fun dec() {
+}
+
+fun component1() {
+}
+
+fun component100() {
+}
+
+fun equals() {
+}
+
+fun invoke() {
+}
+
+fun iterator() {
+}
+
+fun compareTo() {
+}
+
+fun get() {
+}
+
+fun set() {
+}
+
+fun plusAssign() {
+}