fix quickinfo of narrowed private filed (microsoft#43356)

* fix quickinfo of narrowed private filed

* add test case.

* adapt review.

Author: ShuiRuTian

src/compiler/checker.ts

@@ -23733,7 +23733,7 @@ namespace ts {
             // an dotted name expression, and if the location is not an assignment target, obtain the type
             // of the expression (which will reflect control flow analysis). If the expression indeed
             // resolved to the given symbol, return the narrowed type.
-            if (location.kind === SyntaxKind.Identifier) {
+            if (location.kind === SyntaxKind.Identifier || location.kind === SyntaxKind.PrivateIdentifier) {
                 if (isRightSideOfQualifiedNameOrPropertyAccess(location)) {
                     location = location.parent;
                 }

tests/cases/fourslash/quickInfoOnNarrowedType.ts

@@ -18,13 +18,26 @@
 ////   /*6*/s;
 ////}
 
+////class Foo {
+////    #privateProperty: string[] | null;
+////    constructor() {
+////        this.#privateProperty = null;
+////    }
+////    testMethod() {
+////        if (this.#privateProperty === null)
+////            return;
+////        this./*7*/#privateProperty;
+////    }
+////}
+
 verify.quickInfos({
     1: "(parameter) strOrNum: string | number",
     2: "(parameter) strOrNum: number",
     3: "(parameter) strOrNum: string",
     4: "let s: string | undefined",
     5: "let s: string | undefined",
     6: "let s: string",
+    7: "(property) Foo.#privateProperty: string[]"
 });
 
 verify.completions(
@@ -33,4 +46,5 @@ verify.completions(
     { marker: "3", includes: { name: "strOrNum", text: "(parameter) strOrNum: string" } },
     { marker: ["4", "5"], includes: { name: "s", text: "let s: string | undefined" } },
     { marker: "6", includes: { name: "s", text: "let s: string" } },
+    { marker: "7", includes: { name: "#privateProperty", text: "(property) Foo.#privateProperty: string[]" } }
 );