Use more correct check for the constructor symbol

- add test for extension function receiver

idea/idea-completion/testData/basic/common/primitiveCompletion/implicitReceiverFromExtensionMethod.kt

@@ -0,0 +1,14 @@
+class A {
+    fun aaa() {}
+    val aa = 10
+}
+
+fun A.aaaExt() {}
+
+fun A.test() {
+    <caret>
+}
+
+// EXIST: aaa
+// EXIST: aa
+// EXIST: aaaExt

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/JSBasicCompletionTestGenerated.java

@@ -2277,6 +2277,11 @@ public class JSBasicCompletionTestGenerated extends AbstractJSBasicCompletionTes
                 runTest("idea/idea-completion/testData/basic/common/primitiveCompletion/implicitReceiverCompletion.kt");
             }
 
+            @TestMetadata("implicitReceiverFromExtensionMethod.kt")
+            public void testImplicitReceiverFromExtensionMethod() throws Exception {
+                runTest("idea/idea-completion/testData/basic/common/primitiveCompletion/implicitReceiverFromExtensionMethod.kt");
+            }
+
             @TestMetadata("localVariablesAndFunctions.kt")
             public void testLocalVariablesAndFunctions() throws Exception {
                 runTest("idea/idea-completion/testData/basic/common/primitiveCompletion/localVariablesAndFunctions.kt");

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/JvmBasicCompletionTestGenerated.java

@@ -2277,6 +2277,11 @@ public class JvmBasicCompletionTestGenerated extends AbstractJvmBasicCompletionT
                 runTest("idea/idea-completion/testData/basic/common/primitiveCompletion/implicitReceiverCompletion.kt");
             }
 
+            @TestMetadata("implicitReceiverFromExtensionMethod.kt")
+            public void testImplicitReceiverFromExtensionMethod() throws Exception {
+                runTest("idea/idea-completion/testData/basic/common/primitiveCompletion/implicitReceiverFromExtensionMethod.kt");
+            }
+
             @TestMetadata("localVariablesAndFunctions.kt")
             public void testLocalVariablesAndFunctions() throws Exception {
                 runTest("idea/idea-completion/testData/basic/common/primitiveCompletion/localVariablesAndFunctions.kt");

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/completion/KotlinFirCompletionContributor.kt

@@ -10,11 +10,13 @@ import com.intellij.codeInsight.lookup.LookupElementBuilder
 import com.intellij.patterns.PlatformPatterns
 import com.intellij.util.ProcessingContext
 import org.jetbrains.kotlin.fir.declarations.FirFile
+import org.jetbrains.kotlin.fir.declarations.FirTypeParametersOwner
 import org.jetbrains.kotlin.fir.expressions.FirQualifiedAccessExpression
 import org.jetbrains.kotlin.fir.resolve.ScopeSession
 import org.jetbrains.kotlin.fir.resolve.scope
 import org.jetbrains.kotlin.fir.scopes.FirScope
 import org.jetbrains.kotlin.fir.symbols.impl.FirCallableSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirConstructorSymbol
 import org.jetbrains.kotlin.fir.typeContext
 import org.jetbrains.kotlin.fir.types.ConeKotlinType
 import org.jetbrains.kotlin.fir.types.coneTypeUnsafe
@@ -87,8 +89,8 @@ private object KotlinFirCompletionProvider : CompletionProvider<CompletionParame
         }
 
         for (symbol in symbols) {
+            if (symbol is FirConstructorSymbol) continue
             val symbolName = symbol.callableId.callableName
-            if (symbolName.isConstructor) continue
 
             result.addElement(LookupElementBuilder.create(symbolName.toString()))
         }
@@ -98,8 +100,6 @@ private object KotlinFirCompletionProvider : CompletionProvider<CompletionParame
 
 private val FirCallableSymbol<*>.isExtension get() = fir.receiverTypeRef != null
 
-private val Name.isConstructor get() = this == Name.special("<init>")
-
 private fun FirScope.collectCallableSymbols(): MutableList<FirCallableSymbol<*>> {
     val allCallableSymbols = mutableListOf<FirCallableSymbol<*>>()
     fun symbolsCollector(symbol: FirCallableSymbol<*>) {