[FIR] KT-56212 Fix compilation exception caused by type parameter chain

- `FirTypeResolverImpl.resolveSymbol` cannot simply assert that a type
  parameter only has a single qualifier, because code may be fed to the
  compiler where a type parameter is the start of a type chain (see for
  example the added `typeParameterChainInReturnType` test).
- The fix assumes that any multi-qualifier type parameter trivially
  resolves to `null`, because such a chained type cannot exist.

^KT-56212 fixed
^KTIJ-24083 fixed

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosisCompilerTestFE10TestdataTestGenerated.java

@@ -33086,6 +33086,18 @@ public class DiagnosisCompilerTestFE10TestdataTestGenerated extends AbstractDiag
                 runTest("compiler/testData/diagnostics/tests/typeParameters/typeMismatchErrorHasExpectedGenericTypeArgumentInsteadOfTypeParameter.kt");
             }
 
+            @Test
+            @TestMetadata("typeParameterChainInReceiver.kt")
+            public void testTypeParameterChainInReceiver() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/typeParameters/typeParameterChainInReceiver.kt");
+            }
+
+            @Test
+            @TestMetadata("typeParameterChainInReturnType.kt")
+            public void testTypeParameterChainInReturnType() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/typeParameters/typeParameterChainInReturnType.kt");
+            }
+
             @Test
             @TestMetadata("upperBoundCannotBeArray.kt")
             public void testUpperBoundCannotBeArray() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsTestGenerated.java

@@ -33182,6 +33182,18 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                 runTest("compiler/testData/diagnostics/tests/typeParameters/typeMismatchErrorHasExpectedGenericTypeArgumentInsteadOfTypeParameter.kt");
             }
 
+            @Test
+            @TestMetadata("typeParameterChainInReceiver.kt")
+            public void testTypeParameterChainInReceiver() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/typeParameters/typeParameterChainInReceiver.kt");
+            }
+
+            @Test
+            @TestMetadata("typeParameterChainInReturnType.kt")
+            public void testTypeParameterChainInReturnType() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/typeParameters/typeParameterChainInReturnType.kt");
+            }
+
             @Test
             @TestMetadata("upperBoundCannotBeArray.kt")
             public void testUpperBoundCannotBeArray() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsWithLightTreeTestGenerated.java

@@ -33086,6 +33086,18 @@ public class FirOldFrontendDiagnosticsWithLightTreeTestGenerated extends Abstrac
                 runTest("compiler/testData/diagnostics/tests/typeParameters/typeMismatchErrorHasExpectedGenericTypeArgumentInsteadOfTypeParameter.kt");
             }
 
+            @Test
+            @TestMetadata("typeParameterChainInReceiver.kt")
+            public void testTypeParameterChainInReceiver() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/typeParameters/typeParameterChainInReceiver.kt");
+            }
+
+            @Test
+            @TestMetadata("typeParameterChainInReturnType.kt")
+            public void testTypeParameterChainInReturnType() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/typeParameters/typeParameterChainInReturnType.kt");
+            }
+
             @Test
             @TestMetadata("upperBoundCannotBeArray.kt")
             public void testUpperBoundCannotBeArray() throws Exception {

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/providers/impl/FirTypeResolverImpl.kt

@@ -73,10 +73,7 @@ class FirTypeResolverImpl(private val session: FirSession) : FirTypeResolver() {
                         ?: qualifierResolver.resolveEnumEntrySymbol(qualifier, symbol.classId)
                 }
             }
-            is FirTypeParameterSymbol -> {
-                assert(qualifier.size == 1)
-                symbol
-            }
+            is FirTypeParameterSymbol -> symbol.takeIf { qualifier.size == 1 }
             else -> error("!")
         }
     }

compiler/testData/diagnostics/tests/typeParameters/typeParameterChainInReceiver.fir.kt

@@ -0,0 +1,2 @@
+// ISSUE: KT-56212
+fun <F> <!UNRESOLVED_REFERENCE!>F.X<!>.f(): Boolean = false

compiler/testData/diagnostics/tests/typeParameters/typeParameterChainInReceiver.kt

@@ -0,0 +1,2 @@
+// ISSUE: KT-56212
+fun <F> F.<!UNRESOLVED_REFERENCE!>X<!>.f(): Boolean = false

compiler/testData/diagnostics/tests/typeParameters/typeParameterChainInReceiver.txt

@@ -0,0 +1,3 @@
+package
+
+public fun </*0*/ F> [Error type: Unresolved type for F.X].f(): kotlin.Boolean

compiler/testData/diagnostics/tests/typeParameters/typeParameterChainInReturnType.fir.kt

@@ -0,0 +1,2 @@
+// ISSUE: KT-56212
+fun <F> foo(): <!UNRESOLVED_REFERENCE!>F.X<!> = TODO()

compiler/testData/diagnostics/tests/typeParameters/typeParameterChainInReturnType.kt

@@ -0,0 +1,2 @@
+// ISSUE: KT-56212
+fun <F> foo(): F.<!UNRESOLVED_REFERENCE!>X<!> = TODO()

compiler/testData/diagnostics/tests/typeParameters/typeParameterChainInReturnType.txt

@@ -0,0 +1,3 @@
+package
+
+public fun </*0*/ F> foo(): [Error type: Unresolved type for F.X]

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java

@@ -33182,6 +33182,18 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/typeParameters/typeMismatchErrorHasExpectedGenericTypeArgumentInsteadOfTypeParameter.kt");
             }
 
+            @Test
+            @TestMetadata("typeParameterChainInReceiver.kt")
+            public void testTypeParameterChainInReceiver() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/typeParameters/typeParameterChainInReceiver.kt");
+            }
+
+            @Test
+            @TestMetadata("typeParameterChainInReturnType.kt")
+            public void testTypeParameterChainInReturnType() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/typeParameters/typeParameterChainInReturnType.kt");
+            }
+
             @Test
             @TestMetadata("upperBoundCannotBeArray.kt")
             public void testUpperBoundCannotBeArray() throws Exception {