don't parse lines starting with @ as KDoc tags if they're inside a Markdown code fence

#KT-11789 Fixed

compiler/tests/org/jetbrains/kotlin/kdoc/AbstractKDocLexerTest.kt

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2010-2016 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.kdoc
+
+import com.intellij.lang.TokenWrapper
+import com.intellij.lexer.Lexer
+import com.intellij.openapi.util.text.StringUtil
+import junit.framework.TestCase
+import org.jetbrains.kotlin.kdoc.lexer.KDocLexer
+import org.jetbrains.kotlin.test.testFramework.KtUsefulTestCase
+import java.io.File
+
+abstract class AbstractKDocLexerTest : TestCase() {
+    protected fun doTest(fileName: String) {
+        val text = File(fileName).readText()
+        val lexerResult = printTokens(text, 0, KDocLexer())
+        KtUsefulTestCase.assertSameLinesWithFile(fileName.replaceAfterLast(".", "txt"), lexerResult)
+    }
+
+    fun printTokens(text: CharSequence, start: Int, lexer: Lexer): String {
+        lexer.start(text, start, text.length)
+        var result = ""
+        while (true) {
+            val tokenType = lexer.tokenType ?: break
+            val tokenText = getTokenText(lexer)
+            val tokenTypeName = tokenType.toString()
+            val line = "$tokenTypeName ('$tokenText')\n"
+            result += line
+            lexer.advance()
+        }
+        return result
+    }
+
+    private fun getTokenText(lexer: Lexer): String {
+        val tokenType = lexer.tokenType
+        if (tokenType is TokenWrapper) {
+            return tokenType.value
+        }
+
+        var text = lexer.bufferSequence.subSequence(lexer.tokenStart, lexer.tokenEnd).toString()
+        text = StringUtil.replace(text, "\n", "\\n")
+        return text
+    }
+}