Reuse type nodes from optional parameters even when not written as a union with undefined (#48605)

* Reuse type nodes from optional parameters and properties even when not written as a union with `undefined`

* Remove newly unneeded NodeBuilderFlag

* Update public API

* Update baselines from main

src/compiler/checker.ts

@@ -5915,9 +5915,6 @@ namespace ts {
                 if (parameterDeclaration && isRequiredInitializedParameter(parameterDeclaration)) {
                     parameterType = getOptionalType(parameterType);
                 }
-                if ((context.flags & NodeBuilderFlags.NoUndefinedOptionalParameterType) && parameterDeclaration && !isJSDocParameterTag(parameterDeclaration) && isOptionalUninitializedParameter(parameterDeclaration)) {
-                    parameterType = getTypeWithFacts(parameterType, TypeFacts.NEUndefined);
-                }
                 const parameterTypeNode = serializeTypeForDeclaration(context, parameterType, parameterSymbol, context.enclosingDeclaration, privateSymbolVisitor, bundledImports);
 
                 const modifiers = !(context.flags & NodeBuilderFlags.OmitParameterModifiers) && preserveModifierFlags && parameterDeclaration && parameterDeclaration.modifiers ? parameterDeclaration.modifiers.map(factory.cloneNode) : undefined;
@@ -6544,7 +6541,7 @@ namespace ts {
                     if (declWithExistingAnnotation && !isFunctionLikeDeclaration(declWithExistingAnnotation) && !isGetAccessorDeclaration(declWithExistingAnnotation)) {
                         // try to reuse the existing annotation
                         const existing = getEffectiveTypeAnnotationNode(declWithExistingAnnotation)!;
-                        if (getTypeFromTypeNode(existing) === type && existingTypeNodeIsNotReferenceOrIsReferenceWithCompatibleTypeArgumentCount(existing, type)) {
+                        if (typeNodeIsEquivalentToType(existing, declWithExistingAnnotation, type) && existingTypeNodeIsNotReferenceOrIsReferenceWithCompatibleTypeArgumentCount(existing, type)) {
                             const result = serializeExistingTypeNode(context, existing, includePrivateSymbol, bundled);
                             if (result) {
                                 return result;
@@ -6562,6 +6559,17 @@ namespace ts {
                 return result;
             }
 
+            function typeNodeIsEquivalentToType(typeNode: TypeNode, annotatedDeclaration: Declaration, type: Type) {
+                const typeFromTypeNode = getTypeFromTypeNode(typeNode);
+                if (typeFromTypeNode === type) {
+                    return true;
+                }
+                if (isParameter(annotatedDeclaration) && annotatedDeclaration.questionToken) {
+                    return getTypeWithFacts(type, TypeFacts.NEUndefined) === typeFromTypeNode;
+                }
+                return false;
+            }
+
             function serializeReturnTypeForSignature(context: NodeBuilderContext, type: Type, signature: Signature, includePrivateSymbol?: (s: Symbol) => void, bundled?: boolean) {
                 if (!isErrorType(type) && context.enclosingDeclaration) {
                     const annotation = signature.declaration && getEffectiveReturnTypeNode(signature.declaration);
@@ -42579,12 +42587,6 @@ namespace ts {
                 hasSyntacticModifier(parameter, ModifierFlags.ParameterPropertyModifier);
         }
 
-        function isOptionalUninitializedParameter(parameter: ParameterDeclaration) {
-            return !!strictNullChecks &&
-                isOptionalParameter(parameter) &&
-                !parameter.initializer;
-        }
-
         function isExpandoFunctionDeclaration(node: Declaration): boolean {
             const declaration = getParseTreeNode(node, isFunctionDeclaration);
             if (!declaration) {

src/compiler/types.ts

@@ -4490,7 +4490,6 @@ namespace ts {
         UseAliasDefinedOutsideCurrentScope      = 1 << 14,  // Allow non-visible aliases
         UseSingleQuotesForStringLiteralType     = 1 << 28,  // Use single quotes for string literal type
         NoTypeReduction                         = 1 << 29,  // Don't call getReducedType
-        NoUndefinedOptionalParameterType        = 1 << 30,  // Do not add undefined to optional parameter type
 
         // Error handling
         AllowThisInObjectLiteral                = 1 << 15,

src/compiler/utilities.ts

@@ -7654,4 +7654,8 @@ namespace ts {
 
         return state > States.NodeModules ? { topLevelNodeModulesIndex, topLevelPackageNameIndex, packageRootIndex, fileNameIndex } : undefined;
     }
+
+    export function getParameterTypeNode(parameter: ParameterDeclaration | JSDocParameterTag) {
+        return parameter.kind === SyntaxKind.JSDocParameterTag ? parameter.typeExpression?.type : parameter.type;
+    }
 }

src/services/codefixes/helpers.ts

@@ -194,7 +194,6 @@ namespace ts.codefix {
         const scriptTarget = getEmitScriptTarget(program.getCompilerOptions());
         const flags =
             NodeBuilderFlags.NoTruncation
-            | NodeBuilderFlags.NoUndefinedOptionalParameterType
             | NodeBuilderFlags.SuppressAnyReturnType
             | NodeBuilderFlags.AllowEmptyTuple
             | (quotePreference === QuotePreference.Single ? NodeBuilderFlags.UseSingleQuotesForStringLiteralType : NodeBuilderFlags.None);