[microsoftGH-43213] Fix duplicate comments printed in quick info section (microsoft#43240)

* Concat on unique values

* more changes

* only push values to array if unique

* address review comments

* Fix lint

* removw foeachunique

Author: hahmadia

src/services/services.ts

@@ -581,11 +581,17 @@ namespace ts {
 
         let doc = JsDoc.getJsDocCommentsFromDeclarations(declarations);
         if (checker && (doc.length === 0 || declarations.some(hasJSDocInheritDocTag))) {
-            forEachUnique(declarations, declaration => {
-                const inheritedDocs = findBaseOfDeclaration(checker, declaration, symbol => symbol.getDocumentationComment(checker));
+            const seenSymbols = new Set<Symbol>();
+            for (const declaration of declarations) {
+                const inheritedDocs = findBaseOfDeclaration(checker, declaration, symbol => {
+                    if (!seenSymbols.has(symbol)) {
+                        seenSymbols.add(symbol);
+                        return symbol.getDocumentationComment(checker);
+                    }
+                });
                 // TODO: GH#16312 Return a ReadonlyArray, avoid copying inheritedDocs
                 if (inheritedDocs) doc = doc.length === 0 ? inheritedDocs.slice() : inheritedDocs.concat(lineBreakPart(), doc);
-            });
+            }
         }
         return doc;
     }

tests/cases/fourslash/server/quickinfoWrongComment.ts

@@ -0,0 +1,18 @@
+/// <reference path="../fourslash.ts"/>
+
+//// interface I {
+////     /** The colour */
+////     readonly colour: string
+//// }
+//// interface A extends I {
+////     readonly colour: "red" | "green";
+//// }
+//// interface B extends I {
+////     readonly colour: "yellow" | "green";
+//// }
+//// type F = A | B
+//// const f: F = { colour: "green" }
+//// f.colour/*1*/
+
+goTo.marker("1")
+verify.quickInfoIs("(property) colour: \"red\" | \"green\" | \"yellow\"", "The colour")