Completion: don't propose the same name for arguments of lambda (KT-9792)

#KT-9792 Fixed

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/LambdaSignatureTemplates.kt

@@ -154,6 +154,7 @@ object LambdaSignatureTemplates {
             template.addTextSegment("{ ")
         }
 
+        val noNameParameterCount = mutableMapOf<KotlinType, Int>()
         for ((i, parameterType) in parameterTypes.withIndex()) {
             if (i > 0) {
                 template.addTextSegment(", ")
@@ -168,7 +169,10 @@ object LambdaSignatureTemplates {
                 }
             }
             else {
-                val nameSuggestions = nameSuggestions(parameterType)
+                val count = (noNameParameterCount[parameterType] ?: 0) + 1
+                noNameParameterCount[parameterType] = count
+                val suffix = if (count == 1) null else "$count"
+                val nameSuggestions = nameSuggestions(parameterType, suffix)
                 object : Expression() {
                     override fun calculateResult(context: ExpressionContext?) = TextResult(nameSuggestions[0])
                     override fun calculateQuickResult(context: ExpressionContext?): Result? = null
@@ -193,7 +197,11 @@ object LambdaSignatureTemplates {
         return template
     }
 
-    private fun nameSuggestions(parameterType: KotlinType) = KotlinNameSuggester.suggestNamesByType(parameterType, { true }, "p")
+    private fun nameSuggestions(parameterType: KotlinType, suffix: String? = null): List<String> {
+        val suggestions = KotlinNameSuggester.suggestNamesByType(parameterType, { true }, "p")
+        return if (suffix != null) suggestions.map { "$it$suffix" } else suggestions
+    }
+    
     private fun nameSuggestion(parameterType: KotlinType) = nameSuggestions(parameterType)[0]
 
     private fun functionParameterTypes(functionType: KotlinType): List<KotlinType> {

idea/idea-completion/testData/handlers/basic/highOrderFunctions/SameTypeParameters.kt

@@ -0,0 +1,9 @@
+fun foo(f: (Int, Int, Int) -> Unit) {
+}
+
+fun main() {
+    foo<caret>
+}
+
+// ELEMENT: foo
+// TAIL_TEXT: " { Int, Int, Int -> ... } (f: (Int, Int, Int) -> Unit) (<root>)"

idea/idea-completion/testData/handlers/basic/highOrderFunctions/SameTypeParameters.kt.after

@@ -0,0 +1,9 @@
+fun foo(f: (Int, Int, Int) -> Unit) {
+}
+
+fun main() {
+    foo { i, i2, i3 -> <caret> }
+}
+
+// ELEMENT: foo
+// TAIL_TEXT: " { Int, Int, Int -> ... } (f: (Int, Int, Int) -> Unit) (<root>)"

idea/idea-completion/testData/handlers/basic/highOrderFunctions/SameTypeParameters2.kt

@@ -0,0 +1,9 @@
+fun bar(f: (Int, String, Int, String) -> Unit) {
+}
+
+fun main() {
+    bar<caret>
+}
+
+// ELEMENT: bar
+// TAIL_TEXT: " { Int, String, Int, String -> ... } (f: (Int, String, Int, String) -> Unit) (<root>)"

idea/idea-completion/testData/handlers/basic/highOrderFunctions/SameTypeParameters2.kt.after

@@ -0,0 +1,9 @@
+fun bar(f: (Int, String, Int, String) -> Unit) {
+}
+
+fun main() {
+    bar { i, s, i2, s2 -> <caret> }
+}
+
+// ELEMENT: bar
+// TAIL_TEXT: " { Int, String, Int, String -> ... } (f: (Int, String, Int, String) -> Unit) (<root>)"

idea/idea-completion/testData/handlers/basic/highOrderFunctions/SameTypeParameters3.kt

@@ -0,0 +1,9 @@
+fun baz(f: (a: Int, b: String, Int, String, Int, String) -> Unit) {
+}
+
+fun main() {
+    baz<caret>
+}
+
+// ELEMENT: baz
+// TAIL_TEXT: " { a, b, Int, String, Int, String -> ... } (f: (Int, String, Int, String, Int, String) -> Unit) (<root>)"

idea/idea-completion/testData/handlers/basic/highOrderFunctions/SameTypeParameters3.kt.after

@@ -0,0 +1,9 @@
+fun baz(f: (a: Int, b: String, Int, String, Int, String) -> Unit) {
+}
+
+fun main() {
+    baz { a, b, i, s, i2, s2 -> <caret> }
+}
+
+// ELEMENT: baz
+// TAIL_TEXT: " { a, b, Int, String, Int, String -> ... } (f: (Int, String, Int, String, Int, String) -> Unit) (<root>)"

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/handlers/BasicCompletionHandlerTestGenerated.java

@@ -410,6 +410,21 @@ public class BasicCompletionHandlerTestGenerated extends AbstractBasicCompletion
             runTest("idea/idea-completion/testData/handlers/basic/highOrderFunctions/ReplaceByLambdaTemplateNoClosingParenth.kt");
         }
 
+        @TestMetadata("SameTypeParameters.kt")
+        public void testSameTypeParameters() throws Exception {
+            runTest("idea/idea-completion/testData/handlers/basic/highOrderFunctions/SameTypeParameters.kt");
+        }
+
+        @TestMetadata("SameTypeParameters2.kt")
+        public void testSameTypeParameters2() throws Exception {
+            runTest("idea/idea-completion/testData/handlers/basic/highOrderFunctions/SameTypeParameters2.kt");
+        }
+
+        @TestMetadata("SameTypeParameters3.kt")
+        public void testSameTypeParameters3() throws Exception {
+            runTest("idea/idea-completion/testData/handlers/basic/highOrderFunctions/SameTypeParameters3.kt");
+        }
+
         @TestMetadata("WithArgsEmptyLambdaAfter.kt")
         public void testWithArgsEmptyLambdaAfter() throws Exception {
             runTest("idea/idea-completion/testData/handlers/basic/highOrderFunctions/WithArgsEmptyLambdaAfter.kt");