Do not approximate DefinitelyNotNullType in public declarations

Because since 1.6 they become normal denotable types

^KT-26245 Fixed

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

@@ -9179,12 +9179,24 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                 KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/diagnostics/tests/explicitDefinitelyNotNull"), Pattern.compile("^(.+)\\.kt$"), Pattern.compile("^(.+)\\.fir\\.kts?$"), true);
             }
 
+            @Test
+            @TestMetadata("approximation.kt")
+            public void testApproximation() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/explicitDefinitelyNotNull/approximation.kt");
+            }
+
             @Test
             @TestMetadata("disabledFeature.kt")
             public void testDisabledFeature() throws Exception {
                 runTest("compiler/testData/diagnostics/tests/explicitDefinitelyNotNull/disabledFeature.kt");
             }
 
+            @Test
+            @TestMetadata("inference.kt")
+            public void testInference() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/explicitDefinitelyNotNull/inference.kt");
+            }
+
             @Test
             @TestMetadata("notApplicable.kt")
             public void testNotApplicable() throws Exception {

compiler/resolution.common/src/org/jetbrains/kotlin/types/AbstractTypeApproximator.kt

@@ -365,7 +365,7 @@ abstract class AbstractTypeApproximator(
             return typeWithErasedNullability
         }
 
-        return if (conf.definitelyNotNullType) {
+        return if (conf.definitelyNotNullType || languageVersionSettings.supportsFeature(LanguageFeature.DefinitelyNotNullTypeParameters)) {
             approximatedOriginalType?.makeDefinitelyNotNullOrNotNull()
         } else {
             if (toSuper)

compiler/testData/diagnostics/tests/explicitDefinitelyNotNull/approximation.fir.kt

@@ -0,0 +1,14 @@
+// !LANGUAGE: +DefinitelyNotNullTypeParameters
+
+fun <T> foo(x: T, y: T!!) = x!!
+
+fun main() {
+    foo<String>("", "").length
+    <!INAPPLICABLE_CANDIDATE!>foo<!><String>("", null).length
+    foo<String?>(null, "").length
+    foo<String?>(null, null).length
+
+    foo("", "").length
+    foo("", null).length
+    foo(null, "").length
+}

compiler/testData/diagnostics/tests/explicitDefinitelyNotNull/approximation.kt

@@ -0,0 +1,14 @@
+// !LANGUAGE: +DefinitelyNotNullTypeParameters
+
+fun <T> foo(x: T, y: T!!) = x!!
+
+fun main() {
+    foo<String>("", "").length
+    foo<String>("", <!NULL_FOR_NONNULL_TYPE!>null<!>).length
+    foo<String?>(null, "").length
+    foo<String?>(null, <!NULL_FOR_NONNULL_TYPE!>null<!>).length
+
+    foo("", "").length
+    foo("", <!NULL_FOR_NONNULL_TYPE!>null<!>).length
+    foo(null, "").length
+}

compiler/testData/diagnostics/tests/explicitDefinitelyNotNull/approximation.txt

@@ -0,0 +1,4 @@
+package
+
+public fun </*0*/ T> foo(/*0*/ x: T, /*1*/ y: T!!): T!!
+public fun main(): kotlin.Unit

compiler/testData/diagnostics/tests/explicitDefinitelyNotNull/inference.fir.kt

@@ -0,0 +1,33 @@
+// !LANGUAGE: +DefinitelyNotNullTypeParameters
+
+fun <T> toDefNotNull(s: T): T!! = s!!
+
+fun <K> removeQuestionMark(x: K?): K = x!!
+
+fun Any.foo() {}
+
+fun <E> expectNN(e: E!!) {}
+
+fun <F> main(x: F, y: F, z: F, w: F, m: F) {
+    val y1 = toDefNotNull(x) // K instead of K!!
+    val y2: F!! = toDefNotNull(x) // K instead of K!!
+    val x1 = removeQuestionMark(x) // T or T!!
+    val x2: F!! = removeQuestionMark(x) // T or T!!
+
+    val z1 = x!!
+    val z2: F!! = y!!
+    val w1 = if (z != null) z else return
+    val w2: F!! = if (w != null) w else return
+
+    y1.<!INAPPLICABLE_CANDIDATE!>foo<!>()
+    y2.<!INAPPLICABLE_CANDIDATE!>foo<!>()
+    x1.foo()
+    x2.<!INAPPLICABLE_CANDIDATE!>foo<!>()
+    z1.foo()
+    z2.<!INAPPLICABLE_CANDIDATE!>foo<!>()
+    w1.foo()
+    w2.<!INAPPLICABLE_CANDIDATE!>foo<!>()
+
+    expectNN(m)
+    expectNN(m!!)
+}

compiler/testData/diagnostics/tests/explicitDefinitelyNotNull/inference.kt

@@ -0,0 +1,33 @@
+// !LANGUAGE: +DefinitelyNotNullTypeParameters
+
+fun <T> toDefNotNull(s: T): T!! = s!!
+
+fun <K> removeQuestionMark(x: K?): K = x!!
+
+fun Any.foo() {}
+
+fun <E> expectNN(e: E!!) {}
+
+fun <F> main(x: F, y: F, z: F, w: F, m: F) {
+    val y1 = toDefNotNull(x) // K instead of K!!
+    val y2: F!! = toDefNotNull(x) // K instead of K!!
+    val x1 = removeQuestionMark(x) // T or T!!
+    val x2: F!! = removeQuestionMark(x) // T or T!!
+
+    val z1 = x!!
+    val z2: F!! = y!!
+    val w1 = if (z != null) <!DEBUG_INFO_SMARTCAST!>z<!> else return
+    val w2: F!! = if (w != null) <!DEBUG_INFO_SMARTCAST!>w<!> else return
+
+    y1.foo()
+    y2.foo()
+    x1.foo()
+    x2.foo()
+    z1.foo()
+    z2.foo()
+    w1.foo()
+    w2.foo()
+
+    expectNN(<!TYPE_MISMATCH!>m<!>)
+    expectNN(m!!)
+}

compiler/testData/diagnostics/tests/explicitDefinitelyNotNull/inference.txt

@@ -0,0 +1,7 @@
+package
+
+public fun </*0*/ E> expectNN(/*0*/ e: E!!): kotlin.Unit
+public fun </*0*/ F> main(/*0*/ x: F, /*1*/ y: F, /*2*/ z: F, /*3*/ w: F, /*4*/ m: F): kotlin.Unit
+public fun </*0*/ K> removeQuestionMark(/*0*/ x: K?): K
+public fun </*0*/ T> toDefNotNull(/*0*/ s: T): T!!
+public fun kotlin.Any.foo(): kotlin.Unit

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

@@ -9185,12 +9185,24 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/diagnostics/tests/explicitDefinitelyNotNull"), Pattern.compile("^(.*)\\.kts?$"), Pattern.compile("^(.+)\\.fir\\.kts?$"), true);
             }
 
+            @Test
+            @TestMetadata("approximation.kt")
+            public void testApproximation() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/explicitDefinitelyNotNull/approximation.kt");
+            }
+
             @Test
             @TestMetadata("disabledFeature.kt")
             public void testDisabledFeature() throws Exception {
                 runTest("compiler/testData/diagnostics/tests/explicitDefinitelyNotNull/disabledFeature.kt");
             }
 
+            @Test
+            @TestMetadata("inference.kt")
+            public void testInference() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/explicitDefinitelyNotNull/inference.kt");
+            }
+
             @Test
             @TestMetadata("notApplicable.kt")
             public void testNotApplicable() throws Exception {