FIR mangler: fix alias-based type handling #KT-42770 Fixed

compiler/fir/fir2ir/jvm-backend/src/org/jetbrains/kotlin/fir/backend/jvm/FirJvmMangleComputer.kt

@@ -14,8 +14,10 @@ import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.render
 import org.jetbrains.kotlin.fir.resolve.firSymbolProvider
+import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
 import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirClassSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirTypeAliasSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.fir.visitors.FirVisitor
@@ -199,6 +201,10 @@ open class FirJvmMangleComputer(
         when (type) {
             is ConeLookupTagBasedType -> {
                 when (val symbol = type.lookupTag.toSymbol(session)) {
+                    is FirTypeAliasSymbol -> {
+                        mangleType(tBuilder, type.fullyExpandedType(session))
+                        return
+                    }
                     is FirClassSymbol -> symbol.fir.accept(copy(MangleMode.FQNAME), false)
                     is FirTypeParameterSymbol -> tBuilder.mangleTypeParameterReference(symbol.fir)
                 }

compiler/fir/fir2ir/tests/org/jetbrains/kotlin/fir/Fir2IrTextTestGenerated.java

@@ -1772,6 +1772,11 @@ public class Fir2IrTextTestGenerated extends AbstractFir2IrTextTest {
             runTest("compiler/testData/ir/irText/firProblems/putIfAbsent.kt");
         }
 
+        @TestMetadata("SignatureClash.kt")
+        public void testSignatureClash() throws Exception {
+            runTest("compiler/testData/ir/irText/firProblems/SignatureClash.kt");
+        }
+
         @TestMetadata("V8ArrayToList.kt")
         public void testV8ArrayToList() throws Exception {
             runTest("compiler/testData/ir/irText/firProblems/V8ArrayToList.kt");