Prohibit having duplicate parameter names in functional types

#KT-15804 Fixed

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java

@@ -79,6 +79,7 @@ public interface Errors {
             DiagnosticFactory1.create(ERROR, FOR_REDECLARATION);
     DiagnosticFactory1<PsiElement, String> PACKAGE_OR_CLASSIFIER_REDECLARATION =
             DiagnosticFactory1.create(ERROR, FOR_REDECLARATION);
+    DiagnosticFactory0<KtParameter> DUPLICATE_PARAMETER_NAME_IN_FUNCTION_TYPE = DiagnosticFactory0.create(ERROR, DECLARATION_NAME);
 
     DiagnosticFactory1<KtDeclaration, CallableMemberDescriptor> EXTENSION_SHADOWED_BY_MEMBER =
             DiagnosticFactory1.create(WARNING, FOR_REDECLARATION);

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java

@@ -114,6 +114,7 @@ public class DefaultErrorMessages {
 
         MAP.put(REDECLARATION, "Conflicting declarations: {0}", commaSeparated(COMPACT_WITH_MODIFIERS));
         MAP.put(PACKAGE_OR_CLASSIFIER_REDECLARATION, "Redeclaration: {0}", STRING);
+        MAP.put(DUPLICATE_PARAMETER_NAME_IN_FUNCTION_TYPE, "Duplicate parameter name in function type");
 
         MAP.put(NAME_SHADOWING, "Name shadowed: {0}", STRING);
         MAP.put(ACCESSOR_PARAMETER_NAME_SHADOWING, "Accessor parameter name 'field' is shadowed by backing field variable");

compiler/frontend/src/org/jetbrains/kotlin/resolve/TypeResolver.kt

@@ -48,6 +48,7 @@ import org.jetbrains.kotlin.resolve.scopes.LexicalScopeKind
 import org.jetbrains.kotlin.resolve.scopes.MemberScope
 import org.jetbrains.kotlin.resolve.scopes.utils.findFirstFromMeAndParent
 import org.jetbrains.kotlin.resolve.source.KotlinSourceElement
+import org.jetbrains.kotlin.resolve.source.getPsi
 import org.jetbrains.kotlin.resolve.source.toSourceElement
 import org.jetbrains.kotlin.storage.LockBasedStorageManager
 import org.jetbrains.kotlin.types.*
@@ -55,6 +56,7 @@ import org.jetbrains.kotlin.types.Variance.*
 import org.jetbrains.kotlin.types.typeUtil.containsTypeAliasParameters
 import org.jetbrains.kotlin.types.typeUtil.containsTypeAliases
 import org.jetbrains.kotlin.types.typeUtil.isArrayOfNothing
+import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
 class TypeResolver(
         private val annotationResolver: AnnotationResolver,
@@ -231,6 +233,7 @@ class TypeResolver(
                 val receiverType = if (receiverTypeRef == null) null else resolveType(c.noBareTypes(), receiverTypeRef)
 
                 val parameterDescriptors = resolveParametersOfFunctionType(type.parameters)
+                checkParametersOfFunctionType(parameterDescriptors)
 
                 val returnTypeRef = type.returnTypeReference
                 val returnType = if (returnTypeRef != null) resolveType(c.noBareTypes(), returnTypeRef)
@@ -245,6 +248,17 @@ class TypeResolver(
                 ))
             }
 
+            private fun checkParametersOfFunctionType(parameterDescriptors: List<VariableDescriptor>) {
+                val parametersByName = parameterDescriptors.filter { !it.name.isSpecial }.groupBy { it.name }
+                for (parametersGroup in parametersByName.values) {
+                    if (parametersGroup.size < 2) continue
+                    for (parameter in parametersGroup) {
+                        val ktParameter = parameter.source.getPsi()?.safeAs<KtParameter>() ?: continue
+                        c.trace.report(DUPLICATE_PARAMETER_NAME_IN_FUNCTION_TYPE.on(ktParameter))
+                    }
+                }
+            }
+
             private fun resolveParametersOfFunctionType(parameters: List<KtParameter>): List<VariableDescriptor> {
                 class ParameterOfFunctionTypeDescriptor(
                         containingDeclaration: DeclarationDescriptor,

compiler/testData/diagnostics/tests/redeclarations/DuplicateParameterNamesInFunctionType.kt

@@ -0,0 +1,7 @@
+fun test0(f: (String, String) -> Unit) {
+    f("", "")
+}
+
+fun test1(f: (<!DUPLICATE_PARAMETER_NAME_IN_FUNCTION_TYPE!>a<!>: Int, <!DUPLICATE_PARAMETER_NAME_IN_FUNCTION_TYPE!>a<!>: Int) -> Unit) {
+    f(1, 1)
+}

compiler/testData/diagnostics/tests/redeclarations/DuplicateParameterNamesInFunctionType.txt

@@ -0,0 +1,4 @@
+package
+
+public fun test0(/*0*/ f: (kotlin.String, kotlin.String) -> kotlin.Unit): kotlin.Unit
+public fun test1(/*0*/ f: (a: kotlin.Int, a: kotlin.Int) -> kotlin.Unit): kotlin.Unit

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -16099,6 +16099,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("DuplicateParameterNamesInFunctionType.kt")
+            public void testDuplicateParameterNamesInFunctionType() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/DuplicateParameterNamesInFunctionType.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("EnumName.kt")
             public void testEnumName() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/EnumName.kt");