Support definitely non-nullable types (#2520)

* Support definitely non-nullable types

[Definitely non-nullable types](https://github.com/Kotlin/KEEP/blob/c72601cf35c1e95a541bb4b230edb474a6d1d1a8/proposals/definitely-non-nullable-types.md) are enabled since Kotlin 1.7

3 files changed, 61 insertions, 0 deletions

diff --git a/plugins/kotlin-as-java/src/main/kotlin/converters/KotlinToJavaConverter.kt b/plugins/kotlin-as-java/src/main/kotlin/converters/KotlinToJavaConverter.kt
index 8ff35781..4a21aeae 100644
--- a/plugins/kotlin-as-java/src/main/kotlin/converters/KotlinToJavaConverter.kt
+++ b/plugins/kotlin-as-java/src/main/kotlin/converters/KotlinToJavaConverter.kt
@@ -305,6 +305,7 @@ private fun Bound.asJava(): Bound = when (this) {
         inner = inner.asJava()
     )
     is Nullable -> copy(inner.asJava())
+    is DefinitelyNonNullable -> copy(inner.asJava())
     is PrimitiveJavaType -> this
     is Void -> this
     is JavaObject -> this
diff --git a/plugins/kotlin-as-java/src/main/kotlin/signatures/JavaSignatureProvider.kt b/plugins/kotlin-as-java/src/main/kotlin/signatures/JavaSignatureProvider.kt
index 2b56a2bf..50dbc1cb 100644
--- a/plugins/kotlin-as-java/src/main/kotlin/signatures/JavaSignatureProvider.kt
+++ b/plugins/kotlin-as-java/src/main/kotlin/signatures/JavaSignatureProvider.kt
@@ -196,6 +196,7 @@ class JavaSignatureProvider internal constructor(ctcc: CommentsToContentConverte
         is Star -> operator("?")
 
         is Nullable -> signatureForProjection(p.inner)
+        is DefinitelyNonNullable -> signatureForProjection(p.inner)
 
         is JavaObject, is Dynamic -> link("Object", DRI("java.lang", "Object"))
         is Void -> text("void")
diff --git a/plugins/kotlin-as-java/src/test/kotlin/KotlinAsJavaSignatureTest.kt b/plugins/kotlin-as-java/src/test/kotlin/KotlinAsJavaSignatureTest.kt
new file mode 100644
index 00000000..5f755ff3
--- /dev/null
+++ b/plugins/kotlin-as-java/src/test/kotlin/KotlinAsJavaSignatureTest.kt
@@ -0,0 +1,59 @@
+package kotlinAsJavaPlugin
+
+import org.jetbrains.dokka.DokkaConfiguration
+import org.jetbrains.dokka.base.testApi.testRunner.BaseAbstractTest
+import org.jetbrains.dokka.jdk
+import org.junit.jupiter.api.Test
+import signatures.firstSignature
+import signatures.renderedContent
+import utils.*
+
+class KotlinAsJavaSignatureTest : BaseAbstractTest() {
+
+    private val configuration = dokkaConfiguration {
+        sourceSets {
+            sourceSet {
+                sourceRoots = listOf("src/")
+                externalDocumentationLinks = listOf(
+                    DokkaConfiguration.ExternalDocumentationLink.jdk(8),
+                    stdlibExternalDocumentationLink
+                )
+            }
+        }
+    }
+
+    @Suppress("SameParameterValue")
+    private fun source(signature: String) =
+        """
+            |/src/main/kotlin/kotlinAsJavaPlugin/Test.kt
+            |package kotlinAsJavaPlugin
+            |
+            | $signature
+            """.trimIndent()
+
+    @Test
+    fun `fun with definitely non-nullable types as java`() {
+        val source = source("fun <T> elvisLike(x: T, y: T & Any): T & Any = x ?: y")
+        val writerPlugin = TestOutputWriterPlugin()
+
+        testInline(
+            source,
+            configuration,
+            pluginOverrides = listOf(writerPlugin)
+        ) {
+            renderingStage = { _, _ ->
+                val signature = writerPlugin.writer.renderedContent("root/kotlinAsJavaPlugin/-test-kt/elvis-like.html").firstSignature()
+                signature.match(
+                    "public final static ", Span("T"), A("elvisLike"),
+                    "<T extends ", A("Any"), ">(",
+                    Span(
+                        Span(Span(), " x, "),
+                        Span(Span(), " y")
+                    ),
+                    ")", Span(),
+                    ignoreSpanWithTokenStyle = true
+                )
+            }
+        }
+    }
+}
\ No newline at end of file