Mark deprecated items as deprecated in completion lists

Author: fwcd

server/src/main/kotlin/org/javacs/kt/completion/Completions.kt

@@ -3,6 +3,7 @@ package org.javacs.kt.completion
 import com.google.common.cache.CacheBuilder
 import org.eclipse.lsp4j.CompletionItem
 import org.eclipse.lsp4j.CompletionItemKind
+import org.eclipse.lsp4j.CompletionItemTag
 import org.eclipse.lsp4j.CompletionList
 import org.javacs.kt.CompiledFile
 import org.javacs.kt.LOG
@@ -13,6 +14,7 @@ import org.javacs.kt.util.noResult
 import org.javacs.kt.util.stringDistance
 import org.javacs.kt.util.toPath
 import org.javacs.kt.util.onEachIndexed
+import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.container.get
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.js.resolve.diagnostics.findPsi
@@ -109,6 +111,10 @@ private fun completionItem(d: DeclarationDescriptor, surroundingElement: KtEleme
         result.filterText = name
     }
 
+    if (KotlinBuiltIns.isDeprecated(d)) {
+        result.tags = listOf(CompletionItemTag.Deprecated)
+    }
+
     val matchCall = callPattern.matchEntire(result.insertText)
     if (file.lineAfter(surroundingElement.endOffset).startsWith("(") && matchCall != null) {
         result.insertText = matchCall.groups[1]!!.value