Introduce inspection for unused main parameter #KT-26999 Fixed

compiler/frontend/src/org/jetbrains/kotlin/cfg/ControlFlowInformationProvider.kt

@@ -671,8 +671,18 @@ class ControlFlowInformationProvider private constructor(
                 val mainFunctionDetector = MainFunctionDetector(trace.bindingContext, languageVersionSettings)
                 val isMain = owner is KtNamedFunction && mainFunctionDetector.isMain(owner)
                 val functionName = functionDescriptor.name
-                if (isMain && !languageVersionSettings.supportsFeature(LanguageFeature.WarningOnMainUnusedParameter)
-                    || functionDescriptor.isOverridableOrOverrides
+                if (isMain) {
+                    when {
+                        !languageVersionSettings.supportsFeature(LanguageFeature.ExtendedMainConvention) -> {
+                            return
+                        }
+                        !languageVersionSettings.supportsFeature(LanguageFeature.WarningOnMainUnusedParameter) -> {
+                            trace.record(UNUSED_MAIN_PARAMETER, element)
+                            return
+                        }
+                    }
+                }
+                if (functionDescriptor.isOverridableOrOverrides
                     || owner.hasModifier(KtTokens.OVERRIDE_KEYWORD)
                     || OperatorNameConventions.GET_VALUE == functionName
                     || OperatorNameConventions.SET_VALUE == functionName

compiler/frontend/src/org/jetbrains/kotlin/resolve/BindingContext.java

@@ -103,6 +103,7 @@ public interface BindingContext {
     WritableSlice<KtExpression, DataFlowInfo> DATAFLOW_INFO_AFTER_CONDITION = Slices.createSimpleSlice();
     WritableSlice<VariableDescriptor, DataFlowValue> BOUND_INITIALIZER_VALUE = Slices.createSimpleSlice();
     WritableSlice<KtExpression, LeakingThisDescriptor> LEAKING_THIS = Slices.createSimpleSlice();
+    WritableSlice<KtParameter, Boolean> UNUSED_MAIN_PARAMETER = Slices.createSimpleSlice();
 
     /**
      * A qualifier corresponds to a receiver expression (if any). For 'A.B' qualifier is recorded for 'A'.