Avoid deleting properties on global varNodes [perf]

lib/serialize/output.js

@@ -492,13 +492,12 @@ module.exports = {
 		if (globalVars.length > 0) {
 			if (this.options.inline) {
 				const usedGlobalVars = globalVars.filter(({record: globalRecord, node: globalNode}) => {
-					// Can't use `recordNeedsVar()` because some globals are traced and have dependents
-					// even when they're not used
-					if (globalRecord.usageCount === 1) {
-						replaceIdentifier(globalRecord.varNode, globalNode);
-						return false;
-					}
-					return true;
+					// Can't use `recordNeedsVar()` because globals don't have dependents
+					if (globalRecord.usageCount !== 1 || !this.options.inline) return true;
+
+					// Only used once - inline
+					Object.assign(globalRecord.varNode, globalNode);
+					return false;
 				});
 				if (usedGlobalVars.length > 0) localVars.unshift(...usedGlobalVars);
 			} else {
@@ -571,8 +570,10 @@ module.exports = {
 			node = varNode;
 		} else if (isGlobal) {
 			// Global - assign to var. Globals which are only used once are inlined later.
+			// Use a fake `Identifier` node with no `name` property as `varNode`.
+			// If is inlined later, this removes the need to delete the `name` property again.
 			this.globalVars.push({record, node});
-			node = varNode;
+			node = record.varNode = {type: 'Identifier'};
 		} else if (this.recordNeedsVar(record)) {
 			// Used more than once - assign to var.
 			// Wrap unnamed functions in `(0, fn)` to prevent them getting implicitly named.
@@ -813,19 +814,6 @@ function isWrappingMethod(node, keyNode) {
 	return objKeyNode.type === keyType && objKeyNode[valueKey] === keyValue;
 }
 
-/**
- * Replace an identifier node with inline content by mutating identifier node.
- * @param {Object} node - Identifier AST node
- * @param {Object} replacementNode - Replacement AST node
- * @returns {Object} - Input node (now with all props of replacement node)
- */
-function replaceIdentifier(node, replacementNode) {
-	// Identifiers only have 2 properties - `type` and `name`.
-	// `node.type` will be overwritten so no need to delete it.
-	if (!Object.hasOwn(replacementNode, 'name')) delete node.name;
-	return Object.assign(node, replacementNode);
-}
-
 /**
  * Replace a node in place.
  * @param {Object} node - Babel node