FIR: Do not create incorrect synthetic property

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

@@ -29880,6 +29880,12 @@ public class DiagnosisCompilerTestFE10TestdataTestGenerated extends AbstractDiag
                     runTest("compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/nonAsciiSecondChar.kt");
                 }
 
+                @Test
+                @TestMetadata("nonValidFirstChar.kt")
+                public void testNonValidFirstChar() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/nonValidFirstChar.kt");
+                }
+
                 @Test
                 @TestMetadata("OnlyAscii.kt")
                 public void testOnlyAscii() throws Exception {

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

@@ -29880,6 +29880,12 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                     runTest("compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/nonAsciiSecondChar.kt");
                 }
 
+                @Test
+                @TestMetadata("nonValidFirstChar.kt")
+                public void testNonValidFirstChar() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/nonValidFirstChar.kt");
+                }
+
                 @Test
                 @TestMetadata("OnlyAscii.kt")
                 public void testOnlyAscii() throws Exception {

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

@@ -29880,6 +29880,12 @@ public class FirOldFrontendDiagnosticsWithLightTreeTestGenerated extends Abstrac
                     runTest("compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/nonAsciiSecondChar.kt");
                 }
 
+                @Test
+                @TestMetadata("nonValidFirstChar.kt")
+                public void testNonValidFirstChar() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/nonValidFirstChar.kt");
+                }
+
                 @Test
                 @TestMetadata("OnlyAscii.kt")
                 public void testOnlyAscii() throws Exception {

compiler/frontend.java/src/org/jetbrains/kotlin/synthetic/JavaSyntheticPropertiesScope.kt

@@ -146,17 +146,11 @@ class JavaSyntheticPropertiesScope(
         name: Name,
         ownerClass: ClassDescriptor
     ): SyntheticPropertyHolder {
-        if (name.isSpecial) return SyntheticPropertyHolder.EMPTY
+        val possibleGetMethodNames = possibleGetMethodNames(name)
-
+        if (possibleGetMethodNames.isEmpty()) return SyntheticPropertyHolder.EMPTY
-        val identifier = name.identifier
-        if (identifier.isEmpty()) return SyntheticPropertyHolder.EMPTY
-
-        val firstChar = identifier[0]
-        if (!firstChar.isJavaIdentifierStart() || firstChar in 'A'..'Z') return SyntheticPropertyHolder.EMPTY
 
         val memberScope = ownerClass.unsubstitutedMemberScope
 
-        val possibleGetMethodNames = possibleGetMethodNames(name)
         val getMethod = possibleGetMethodNames
             .flatMap { memberScope.getContributedFunctions(it, NoLookupLocation.FROM_SYNTHETIC_SCOPE) }
             .singleOrNull {

compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/nonValidFirstChar.kt

@@ -0,0 +1,14 @@
+// FIR_IDENTICAL
+// SKIP_TXT
+// FILE: A.java
+public class A {
+    public String get1() {
+        return "";
+    }
+}
+
+// FILE: main.kt
+fun foo(a: A) {
+    a.<!UNRESOLVED_REFERENCE!>`1`<!>
+    a.get1()
+}

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

@@ -29976,6 +29976,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                     runTest("compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/nonAsciiSecondChar.kt");
                 }
 
+                @Test
+                @TestMetadata("nonValidFirstChar.kt")
+                public void testNonValidFirstChar() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/syntheticExtensions/javaProperties/nonValidFirstChar.kt");
+                }
+
                 @Test
                 @TestMetadata("OnlyAscii.kt")
                 public void testOnlyAscii() throws Exception {

core/compiler.common.jvm/src/org/jetbrains/kotlin/load/java/propertiesConventionUtil.kt

@@ -65,8 +65,15 @@ fun getPropertyNamesCandidatesByAccessorName(name: Name): List<Name> {
 }
 
 fun possibleGetMethodNames(propertyName: Name): List<Name> {
-    val result = ArrayList<Name>(3)
+    if (propertyName.isSpecial) return emptyList()
+
     val identifier = propertyName.identifier
+    if (identifier.isEmpty()) return emptyList()
+
+    val firstChar = identifier[0]
+    if (!firstChar.isJavaIdentifierStart() || firstChar in 'A'..'Z') return emptyList()
+
+    val result = ArrayList<Name>(3)
 
     if (JvmAbi.startsWithIsPrefix(identifier)) {
         result.add(propertyName)