Revert and always use merged symbol to get members of late bound symbol

Fixes microsoft#30891

Author: sheetalkamat

src/compiler/checker.ts

@@ -6607,11 +6607,12 @@ namespace ts {
          * unique symbol type which we can then use as the name of the member. This allows users
          * to define custom symbols that can be used in the members of an object type.
          *
+         * @param parent The containing symbol for the member.
          * @param earlySymbols The early-bound symbols of the parent.
          * @param lateSymbols The late-bound symbols of the parent.
          * @param decl The member to bind.
          */
-        function lateBindMember(earlySymbols: SymbolTable | undefined, lateSymbols: SymbolTable, decl: LateBoundDeclaration) {
+        function lateBindMember(parent: Symbol, earlySymbols: SymbolTable | undefined, lateSymbols: SymbolTable, decl: LateBoundDeclaration) {
             Debug.assert(!!decl.symbol, "The member is expected to have a symbol.");
             const links = getNodeLinks(decl);
             if (!links.resolvedSymbol) {
@@ -6642,7 +6643,6 @@ namespace ts {
                     }
                     lateSymbol.nameType = type;
                     addDeclarationToLateBoundSymbol(lateSymbol, decl, symbolFlags);
-                    const parent = getSymbolOfNode(decl.parent);
                     if (lateSymbol.parent) {
                         Debug.assert(lateSymbol.parent === parent, "Existing symbol parent should match new one");
                     }
@@ -6652,15 +6652,6 @@ namespace ts {
                     return links.resolvedSymbol = lateSymbol;
                 }
             }
-            else {
-                const type = checkComputedPropertyName(decl.name);
-                if (isTypeUsableAsPropertyName(type)) {
-                    const memberName = getPropertyNameFromType(type);
-                    if (!lateSymbols.has(memberName)) {
-                        lateSymbols.set(memberName, links.resolvedSymbol);
-                    }
-                }
-            }
             return links.resolvedSymbol;
         }
 
@@ -6684,7 +6675,7 @@ namespace ts {
                     if (members) {
                         for (const member of members) {
                             if (isStatic === hasStaticModifier(member) && hasLateBindableName(member)) {
-                                lateBindMember(earlySymbols, lateSymbols, member);
+                                lateBindMember(symbol, earlySymbols, lateSymbols, member);
                             }
                         }
                     }
@@ -6718,11 +6709,12 @@ namespace ts {
                 const links = getSymbolLinks(symbol);
                 if (!links.lateSymbol && some(symbol.declarations, hasLateBindableName)) {
                     // force late binding of members/exports. This will set the late-bound symbol
+                    const parent = getMergedSymbol(symbol.parent)!;
                     if (some(symbol.declarations, hasStaticModifier)) {
-                        getExportsOfSymbol(symbol.parent!);
+                        getExportsOfSymbol(parent);
                     }
                     else {
-                        getMembersOfSymbol(symbol.parent!);
+                        getMembersOfSymbol(parent);
                     }
                 }
                 return links.lateSymbol || (links.lateSymbol = symbol);