Added tests for union types with identical doc comments.

tests/baselines/reference/quickInfoOnUnionPropertiesWithIdenticalJSDocComments01.baseline

@@ -0,0 +1,76 @@
+[
+  {
+    "marker": {
+      "fileName": "/tests/cases/fourslash/quickInfoOnUnionPropertiesWithIdenticalJSDocComments01.ts",
+      "position": 746
+    },
+    "quickInfo": {
+      "kind": "property",
+      "kindModifiers": "optional",
+      "textSpan": {
+        "start": 746,
+        "length": 8
+      },
+      "displayParts": [
+        {
+          "text": "(",
+          "kind": "punctuation"
+        },
+        {
+          "text": "property",
+          "kind": "text"
+        },
+        {
+          "text": ")",
+          "kind": "punctuation"
+        },
+        {
+          "text": " ",
+          "kind": "space"
+        },
+        {
+          "text": "language",
+          "kind": "propertyName"
+        },
+        {
+          "text": "?",
+          "kind": "punctuation"
+        },
+        {
+          "text": ":",
+          "kind": "punctuation"
+        },
+        {
+          "text": " ",
+          "kind": "space"
+        },
+        {
+          "text": "string",
+          "kind": "keyword"
+        }
+      ],
+      "documentation": [
+        {
+          "text": "A language id, like `typescript`.",
+          "kind": "text"
+        },
+        {
+          "text": "\n",
+          "kind": "lineBreak"
+        },
+        {
+          "text": "A language id, like `typescript`.",
+          "kind": "text"
+        },
+        {
+          "text": "\n",
+          "kind": "lineBreak"
+        },
+        {
+          "text": "A language id, like `typescript`.",
+          "kind": "text"
+        }
+      ]
+    }
+  }
+]

tests/cases/fourslash/quickInfoOnUnionPropertiesWithIdenticalJSDocComments01.ts

@@ -0,0 +1,29 @@
+/// <reference path="fourslash.ts" />
+
+////export type DocumentFilter = {
+////    /** A language id, like `typescript`. */
+////    language: string;
+////    /** A Uri [scheme](#Uri.scheme), like `file` or `untitled`. */
+////    scheme?: string;
+////    /** A glob pattern, like `*.{ts,js}`. */
+////    pattern?: string;
+////} | {
+////    /** A language id, like `typescript`. */
+////    language?: string;
+////    /** A Uri [scheme](#Uri.scheme), like `file` or `untitled`. */
+////    scheme: string;
+////    /** A glob pattern, like `*.{ts,js}`. */
+////    pattern?: string;
+////} | {
+////    /** A language id, like `typescript`. */
+////    language?: string;
+////    /** A Uri [scheme](#Uri.scheme), like `file` or `untitled`. */
+////    scheme?: string;
+////    /** A glob pattern, like `*.{ts,js}`. */
+////    pattern: string;
+////};
+////
+////declare let x: DocumentFilter;
+////x./**/language
+
+verify.baselineQuickInfo();