Add test to preserve behaviour

 It's important to have ambiguity in these cases to introduce overload
 resolution by suspend-modifier without breaking changes in future

 Relates to #KT-23610

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

@@ -23222,6 +23222,11 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirOldFronte
             runTest("compiler/testData/diagnostics/tests/suspendConversion/chainedFunSuspendConversionForSimpleExpression.kt");
         }
 
+        @TestMetadata("overloadResolutionBySuspendModifier.kt")
+        public void testOverloadResolutionBySuspendModifier() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/suspendConversion/overloadResolutionBySuspendModifier.kt");
+        }
+
         @TestMetadata("severalConversionsInOneCall.kt")
         public void testSeveralConversionsInOneCall() throws Exception {
             runTest("compiler/testData/diagnostics/tests/suspendConversion/severalConversionsInOneCall.kt");

compiler/testData/diagnostics/tests/suspendConversion/overloadResolutionBySuspendModifier.fir.kt

+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+fun foo(x: () -> Int) {}
+fun foo(x: suspend () -> Int) {}
+
+fun usualCall(): Int = 42
+suspend fun suspendCall(): Int = 42
+
+// it's important to have ambiguity in these cases to introduce overload resolution by suspend modifier in future
+fun test1() {
+    <!AMBIGUITY!>foo<!> { usualCall() }
+    <!AMBIGUITY!>foo<!> { suspendCall() }
+}
+
+// candidate without suspend conversions is more specific
+fun test2(f: () -> Int, g: suspend () -> Int) {
+    foo(f)
+    foo(g)
+}
\ No newline at end of file

compiler/testData/diagnostics/tests/suspendConversion/overloadResolutionBySuspendModifier.kt

+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+fun foo(x: () -> Int) {}
+fun foo(x: suspend () -> Int) {}
+
+fun usualCall(): Int = 42
+suspend fun suspendCall(): Int = 42
+
+// it's important to have ambiguity in these cases to introduce overload resolution by suspend modifier in future
+fun test1() {
+    <!OVERLOAD_RESOLUTION_AMBIGUITY!>foo<!> { usualCall() }
+    <!OVERLOAD_RESOLUTION_AMBIGUITY!>foo<!> { <!ILLEGAL_SUSPEND_FUNCTION_CALL!>suspendCall<!>() }
+}
+
+// candidate without suspend conversions is more specific
+fun test2(f: () -> Int, g: suspend () -> Int) {
+    foo(f)
+    foo(g)
+}
\ No newline at end of file

compiler/testData/diagnostics/tests/suspendConversion/overloadResolutionBySuspendModifier.txt

+package
+
+public fun foo(/*0*/ x: () -> kotlin.Int): kotlin.Unit
+public fun foo(/*0*/ x: suspend () -> kotlin.Int): kotlin.Unit
+public suspend fun suspendCall(): kotlin.Int
+public fun test1(): kotlin.Unit
+public fun test2(/*0*/ f: () -> kotlin.Int, /*1*/ g: suspend () -> kotlin.Int): kotlin.Unit
+public fun usualCall(): kotlin.Int

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -23304,6 +23304,11 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTestWithFirVali
                 runTest("compiler/testData/diagnostics/tests/suspendConversion/chainedFunSuspendConversionForSimpleExpression.kt");
             }
 
+            @TestMetadata("overloadResolutionBySuspendModifier.kt")
+            public void testOverloadResolutionBySuspendModifier() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/suspendConversion/overloadResolutionBySuspendModifier.kt");
+            }
+
             @TestMetadata("severalConversionsInOneCall.kt")
             public void testSeveralConversionsInOneCall() throws Exception {
                 runTest("compiler/testData/diagnostics/tests/suspendConversion/severalConversionsInOneCall.kt");

compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java

@@ -23224,6 +23224,11 @@ public class DiagnosticsUsingJavacTestGenerated extends AbstractDiagnosticsUsing
                 runTest("compiler/testData/diagnostics/tests/suspendConversion/chainedFunSuspendConversionForSimpleExpression.kt");
             }
 
+            @TestMetadata("overloadResolutionBySuspendModifier.kt")
+            public void testOverloadResolutionBySuspendModifier() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/suspendConversion/overloadResolutionBySuspendModifier.kt");
+            }
+
             @TestMetadata("severalConversionsInOneCall.kt")
             public void testSeveralConversionsInOneCall() throws Exception {
                 runTest("compiler/testData/diagnostics/tests/suspendConversion/severalConversionsInOneCall.kt");