Add better handling of functional types in rendered output

core/src/main/kotlin/model/Documentable.kt

@@ -340,12 +340,13 @@ data class DTypeParameter(
     constructor(
         dri: DRI,
         name: String,
+        presentableName: String?,
         documentation: SourceSetDependent<DocumentationNode>,
         expectPresentInSet: DokkaSourceSet?,
         bounds: List<Bound>,
         sourceSets: Set<DokkaSourceSet>,
         extra: PropertyContainer<DTypeParameter> = PropertyContainer.empty()
-    ) : this(Invariance(TypeParameter(dri, name)), documentation, expectPresentInSet, bounds, sourceSets, extra)
+    ) : this(Invariance(TypeParameter(dri, name, presentableName)), documentation, expectPresentInSet, bounds, sourceSets, extra)
 
     override val dri: DRI by variantTypeParameter.inner::dri
     override val name: String by variantTypeParameter.inner::name
@@ -376,13 +377,28 @@ data class DTypeAlias(
 
 sealed class Projection
 sealed class Bound : Projection()
-data class TypeParameter(val dri: DRI, val name: String) : Bound()
+data class TypeParameter(val dri: DRI, val name: String, val presentableName: String? = null) : Bound()
 object Star : Projection()
-data class TypeConstructor(
-    val dri: DRI,
-    val projections: List<Projection>,
-    val modifier: FunctionModifiers = FunctionModifiers.NONE
-) : Bound()
+
+sealed class TypeConstructor : Bound() {
+    abstract val dri: DRI
+    abstract val projections: List<Projection>
+    abstract val presentableName: String?
+}
+
+data class GenericTypeConstructor(
+    override val dri: DRI,
+    override val projections: List<Projection>,
+    override val presentableName: String? = null
+) : TypeConstructor()
+
+data class FunctionalTypeConstructor(
+    override val dri: DRI,
+    override val projections: List<Projection>,
+    val isExtensionFunction: Boolean = false,
+    val isSuspendable: Boolean = false,
+    override val presentableName: String? = null
+) : TypeConstructor()
 
 data class Nullable(val inner: Bound) : Bound()
 
@@ -406,14 +422,10 @@ object JavaObject : Bound()
 object Dynamic : Bound()
 data class UnresolvedBound(val name: String) : Bound()
 
-enum class FunctionModifiers {
-    NONE, FUNCTION, EXTENSION
-}
-
 fun Variance<TypeParameter>.withDri(dri: DRI) = when(this) {
-    is Contravariance -> Contravariance(TypeParameter(dri, inner.name))
-    is Covariance -> Covariance(TypeParameter(dri, inner.name))
-    is Invariance -> Invariance(TypeParameter(dri, inner.name))
+    is Contravariance -> Contravariance(TypeParameter(dri, inner.name, inner.presentableName))
+    is Covariance -> Covariance(TypeParameter(dri, inner.name, inner.presentableName))
+    is Invariance -> Invariance(TypeParameter(dri, inner.name, inner.presentableName))
 }
 
 private fun String.shorten(maxLength: Int) = lineSequence().first().let {

plugins/base/src/main/kotlin/signatures/KotlinSignatureProvider.kt

@@ -323,14 +323,15 @@ class KotlinSignatureProvider(ctcc: CommentsToContentConverter, logger: DokkaLog
         when (p) {
             is TypeParameter -> link(p.name, p.dri)
 
-            is TypeConstructor -> if (p.function)
+            is FunctionalTypeConstructor ->
                 +funType(mainDRI.single(), mainSourcesetData, p)
-            else
+
+            is GenericTypeConstructor ->
                 group(styles = emptySet()) {
                     val linkText = if (showFullyQualifiedName && p.dri.packageName != null) {
                         "${p.dri.packageName}.${p.dri.classNames.orEmpty()}"
                     } else p.dri.classNames.orEmpty()
-
+                    if (p.presentableName != null) text(p.presentableName + ": ")
                     link(linkText, p.dri)
                     list(p.projections, prefix = "<", suffix = ">") {
                         signatureForProjection(it, showFullyQualifiedName)
@@ -357,14 +358,18 @@ class KotlinSignatureProvider(ctcc: CommentsToContentConverter, logger: DokkaLog
             is UnresolvedBound -> text(p.name)
         }
 
-    private fun funType(dri: DRI, sourceSets: Set<DokkaSourceSet>, type: TypeConstructor) =
+    private fun funType(dri: DRI, sourceSets: Set<DokkaSourceSet>, type: FunctionalTypeConstructor) =
         contentBuilder.contentFor(dri, sourceSets, ContentKind.Main) {
-            if (type.extension) {
+
+            if (type.presentableName != null) text(type.presentableName + ": ")
+            if (type.isSuspendable) text("suspend ")
+
+            if (type.isExtensionFunction) {
                 signatureForProjection(type.projections.first())
                 text(".")
             }
 
-            val args = if (type.extension)
+            val args = if (type.isExtensionFunction)
                 type.projections.drop(1)
             else
                 type.projections
@@ -379,16 +384,11 @@ class KotlinSignatureProvider(ctcc: CommentsToContentConverter, logger: DokkaLog
         }
 }
 
-private fun PrimitiveJavaType.translateToKotlin() = TypeConstructor(
+private fun PrimitiveJavaType.translateToKotlin() = GenericTypeConstructor(
     dri = dri,
-    projections = emptyList()
+    projections = emptyList(),
+    presentableName = null
 )
 
 private val DTypeParameter.nontrivialBounds: List<Bound>
     get() = bounds.filterNot { it is Nullable && it.inner.driOrNull == DriOfAny  }
-
-val TypeConstructor.function
-    get() = modifier == FunctionModifiers.FUNCTION || modifier == FunctionModifiers.EXTENSION
-
-val TypeConstructor.extension
-    get() = modifier == FunctionModifiers.EXTENSION

plugins/base/src/main/kotlin/translators/descriptors/DefaultDescriptorToDocumentableTranslator.kt

@@ -17,8 +17,11 @@ import org.jetbrains.dokka.model.properties.PropertyContainer
 import org.jetbrains.dokka.plugability.DokkaContext
 import org.jetbrains.dokka.transformers.sources.SourceToDocumentableTranslator
 import org.jetbrains.dokka.utilities.DokkaLogger
+import org.jetbrains.kotlin.builtins.functions.FunctionClassDescriptor
+import org.jetbrains.kotlin.builtins.isBuiltinExtensionFunctionalType
 import org.jetbrains.kotlin.builtins.isExtensionFunctionType
 import org.jetbrains.kotlin.builtins.isFunctionType
+import org.jetbrains.kotlin.builtins.isSuspendFunctionTypeOrSubtype
 import org.jetbrains.kotlin.codegen.isJvmStaticInObjectOrClassOrInterface
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.descriptors.ClassKind
@@ -586,7 +589,7 @@ private class DokkaDescriptorVisitor(
     private fun ClassDescriptor.resolveClassDescriptionData(): ClassInfo {
 
         fun toTypeConstructor(kt: KotlinType) =
-            TypeConstructor(
+            GenericTypeConstructor(
                 DRI.from(kt.constructor.declarationDescriptor as DeclarationDescriptor),
                 kt.arguments.map { it.toProjection() })
 
@@ -621,7 +624,7 @@ private class DokkaDescriptorVisitor(
     private fun TypeParameterDescriptor.toVariantTypeParameter() =
         DTypeParameter(
             variantTypeParameter(
-                TypeParameter(DRI.from(this), name.identifier)
+                TypeParameter(DRI.from(this), name.identifier, annotations.getPresentableName())
             ),
             resolveDescriptorData(),
             null,
@@ -630,6 +633,10 @@ private class DokkaDescriptorVisitor(
             extra = PropertyContainer.withAll(additionalExtras().toSourceSetDependent().toAdditionalModifiers())
         )
 
+    private fun org.jetbrains.kotlin.descriptors.annotations.Annotations.getPresentableName(): String? =
+        map { it.toAnnotation() }.singleOrNull { it.dri.classNames == "ParameterName" }?.params?.get("name")
+            .safeAs<StringValue>()?.value?.drop(1)?.dropLast(1) // Dropping enclosing doublequotes because we don't want to have it in our custom signature serializer
+
     private fun KotlinType.toBound(): Bound = when (this) {
         is DynamicType -> Dynamic
         is AbbreviatedType -> TypeAliased(
@@ -639,14 +646,20 @@ private class DokkaDescriptorVisitor(
         else -> when (val ctor = constructor.declarationDescriptor) {
             is TypeParameterDescriptor -> TypeParameter(
                 dri = DRI.from(ctor),
-                name = ctor.name.asString()
+                name = ctor.name.asString(),
+                presentableName = annotations.getPresentableName()
+            )
+            is FunctionClassDescriptor -> FunctionalTypeConstructor(
+                DRI.from(ctor),
+                arguments.map { it.toProjection() },
+                isExtensionFunction = isExtensionFunctionType || isBuiltinExtensionFunctionalType,
+                isSuspendable = isSuspendFunctionTypeOrSubtype,
+                presentableName = annotations.getPresentableName()
             )
-            else -> TypeConstructor(
+            else -> GenericTypeConstructor(
                 DRI.from(ctor!!), // TODO: remove '!!'
                 arguments.map { it.toProjection() },
-                if (isExtensionFunctionType) FunctionModifiers.EXTENSION
-                else if (isFunctionType) FunctionModifiers.FUNCTION
-                else FunctionModifiers.NONE
+                annotations.getPresentableName()
             )
         }.let {
             if (isMarkedNullable) Nullable(it) else it

plugins/base/src/main/kotlin/translators/psi/DefaultPsiToDocumentableTranslator.kt

@@ -22,9 +22,11 @@ import org.jetbrains.dokka.plugability.DokkaContext
 import org.jetbrains.dokka.transformers.sources.SourceToDocumentableTranslator
 import org.jetbrains.dokka.utilities.DokkaLogger
 import org.jetbrains.kotlin.asJava.elements.KtLightAbstractAnnotation
+import org.jetbrains.kotlin.builtins.functions.FunctionClassDescriptor
 import org.jetbrains.kotlin.cli.common.CLIConfigurationKeys
 import org.jetbrains.kotlin.cli.jvm.config.JavaSourceRoot
 import org.jetbrains.kotlin.descriptors.Visibilities
+import org.jetbrains.kotlin.idea.caches.resolve.util.getJavaClassDescriptor
 import org.jetbrains.kotlin.idea.refactoring.fqName.getKotlinFqName
 import org.jetbrains.kotlin.load.java.JvmAbi
 import org.jetbrains.kotlin.load.java.propertyNameByGetMethodName
@@ -139,7 +141,7 @@ class DefaultPsiToDocumentableTranslator(
                             psiClass.isInterface -> DRI.from(psiClass) to JavaClassKindTypes.INTERFACE
                             else -> DRI.from(psiClass) to JavaClassKindTypes.CLASS
                         }
-                        TypeConstructor(
+                        GenericTypeConstructor(
                             dri,
                             psi.parameters.map(::getProjection)
                         ) to javaClassKind
@@ -370,11 +372,19 @@ class DefaultPsiToDocumentableTranslator(
                                     dri = DRI.from(resolved),
                                     name = resolved.name.orEmpty()
                                 )
-                            else ->
-                                TypeConstructor(DRI.from(resolved), type.parameters.map { getProjection(it) })
+                            Regex("kotlin\\.jvm\\.functions\\.Function.*").matches(resolved.qualifiedName ?: "") ||
+                                    Regex("java\\.util\\.function\\.Function.*").matches(
+                                        resolved.qualifiedName ?: ""
+                                    ) -> FunctionalTypeConstructor(
+                                DRI.from(resolved),
+                                type.parameters.map { getProjection(it) }
+                            )
+                            else -> GenericTypeConstructor(
+                                DRI.from(resolved),
+                                type.parameters.map { getProjection(it) })
                         }
                     }
-                    is PsiArrayType -> TypeConstructor(
+                    is PsiArrayType -> GenericTypeConstructor(
                         DRI("kotlin", "Array"),
                         listOf(getProjection(type.componentType))
                     )
@@ -411,6 +421,7 @@ class DefaultPsiToDocumentableTranslator(
                 DTypeParameter(
                     dri.copy(target = dri.target.nextTarget()),
                     type.name.orEmpty(),
+                    null,
                     javadocParser.parseDocumentation(type).toSourceSetDependent(),
                     null,
                     mapBounds(type.bounds),