K2: fix an exception during function resolve #KT-59649 Fixed

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

@@ -530,6 +530,12 @@ public class DiagnosticCompilerTestFirTestdataTestGenerated extends AbstractDiag
             runTest("compiler/fir/analysis-tests/testData/resolve/propertyFromJavaPlusAssign.kt");
         }
 
+        @Test
+        @TestMetadata("propertyGetterWithoutType.kt")
+        public void testPropertyGetterWithoutType() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/resolve/propertyGetterWithoutType.kt");
+        }
+
         @Test
         @TestMetadata("qualifierWithCompanion.kt")
         public void testQualifierWithCompanion() throws Exception {

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

@@ -530,6 +530,12 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFirTestDataTestGenerated
             runTest("compiler/fir/analysis-tests/testData/resolve/propertyFromJavaPlusAssign.kt");
         }
 
+        @Test
+        @TestMetadata("propertyGetterWithoutType.kt")
+        public void testPropertyGetterWithoutType() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/resolve/propertyGetterWithoutType.kt");
+        }
+
         @Test
         @TestMetadata("qualifierWithCompanion.kt")
         public void testQualifierWithCompanion() throws Exception {

compiler/fir/analysis-tests/legacy-fir-tests/tests-gen/org/jetbrains/kotlin/fir/LazyBodyIsNotTouchedTestGenerated.java

@@ -449,6 +449,11 @@ public class LazyBodyIsNotTouchedTestGenerated extends AbstractLazyBodyIsNotTouc
         runTest("compiler/fir/analysis-tests/testData/resolve/propertyFromJavaPlusAssign.kt");
     }
 
+    @TestMetadata("propertyGetterWithoutType.kt")
+    public void testPropertyGetterWithoutType() throws Exception {
+        runTest("compiler/fir/analysis-tests/testData/resolve/propertyGetterWithoutType.kt");
+    }
+
     @TestMetadata("qualifierWithCompanion.kt")
     public void testQualifierWithCompanion() throws Exception {
         runTest("compiler/fir/analysis-tests/testData/resolve/qualifierWithCompanion.kt");

compiler/fir/analysis-tests/testData/resolve/propertyGetterWithoutType.fir.txt

@@ -0,0 +1,9 @@
+FILE: propertyGetterWithoutType.kt
+    public final val prop: <ERROR TYPE REF: empty body>
+        public get(): <ERROR TYPE REF: empty body> {
+            local final fun smth(s: R|kotlin/String|): R|kotlin/Int| {
+                ^smth Int(1)
+            }
+
+            ^ R|<local>/smth|(String(awd))
+        }

compiler/fir/analysis-tests/testData/resolve/propertyGetterWithoutType.kt

@@ -0,0 +1,6 @@
+// ISSUE: KT-59649
+val prop
+    get() {
+        fun smth(s: String) = 1
+        return smth("awd")
+    }

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

@@ -530,6 +530,12 @@ public class FirLightTreeDiagnosticsTestGenerated extends AbstractFirLightTreeDi
             runTest("compiler/fir/analysis-tests/testData/resolve/propertyFromJavaPlusAssign.kt");
         }
 
+        @Test
+        @TestMetadata("propertyGetterWithoutType.kt")
+        public void testPropertyGetterWithoutType() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/resolve/propertyGetterWithoutType.kt");
+        }
+
         @Test
         @TestMetadata("qualifierWithCompanion.kt")
         public void testQualifierWithCompanion() throws Exception {

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

@@ -530,6 +530,12 @@ public class FirPsiDiagnosticTestGenerated extends AbstractFirPsiDiagnosticTest
             runTest("compiler/fir/analysis-tests/testData/resolve/propertyFromJavaPlusAssign.kt");
         }
 
+        @Test
+        @TestMetadata("propertyGetterWithoutType.kt")
+        public void testPropertyGetterWithoutType() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/resolve/propertyGetterWithoutType.kt");
+        }
+
         @Test
         @TestMetadata("qualifierWithCompanion.kt")
         public void testQualifierWithCompanion() throws Exception {

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/FirDeclarationsResolveTransformer.kt

@@ -656,7 +656,7 @@ open class FirDeclarationsResolveTransformer(
         val body = result.body
         if (result.returnTypeRef is FirImplicitTypeRef) {
             val simpleFunction = function as? FirSimpleFunction
-            val returnExpression = (body?.statements?.single() as? FirReturnExpression)?.result
+            val returnExpression = (body?.statements?.singleOrNull() as? FirReturnExpression)?.result
             val returnTypeRef = if (returnExpression?.typeRef is FirResolvedTypeRef) {
                 returnExpression.resultType.approximateDeclarationType(
                     session,