Remove two-way mapping from const enums

internal/bundler_tests/snapshots/snapshots_ts.txt

@@ -1739,9 +1739,9 @@ console.log("success");
 TestTSPrintNonFiniteNumberInsideWith
 ---------- /out.js ----------
 var Foo = /* @__PURE__ */ ((Foo2) => {
-  Foo2[Foo2["NAN"] = NaN] = "NAN";
-  Foo2[Foo2["POS_INF"] = Infinity] = "POS_INF";
-  Foo2[Foo2["NEG_INF"] = -Infinity] = "NEG_INF";
+  Foo2["NAN"] = NaN;
+  Foo2["POS_INF"] = Infinity;
+  Foo2["NEG_INF"] = -Infinity;
   return Foo2;
 })(Foo || {});
 //! It's ok to use "NaN" and "Infinity" here

internal/js_ast/js_ast.go

@@ -1030,6 +1030,7 @@ type SEnum struct {
 	Values   []EnumValue
 	Name     ast.LocRef
 	Arg      ast.Ref
+	IsConst  bool
 	IsExport bool
 }
 

internal/js_parser/js_parser.go

@@ -7095,7 +7095,7 @@ func (p *parser) parseStmt(opts parseStmtOpts) js_ast.Stmt {
 		if !p.options.ts.Parse {
 			p.lexer.Unexpected()
 		}
-		return p.parseTypeScriptEnumStmt(loc, opts)
+		return p.parseTypeScriptEnumStmt(loc, opts, false)
 
 	case js_lexer.TAt:
 		// Parse decorators before class statements, which are potentially exported
@@ -7176,7 +7176,7 @@ func (p *parser) parseStmt(opts parseStmtOpts) js_ast.Stmt {
 		p.lexer.Next()
 
 		if p.options.ts.Parse && p.lexer.Token == js_lexer.TEnum {
-			return p.parseTypeScriptEnumStmt(loc, opts)
+			return p.parseTypeScriptEnumStmt(loc, opts, true)
 		}
 
 		decls := p.parseAndDeclareDecls(ast.SymbolConst, opts)
@@ -10940,8 +10940,8 @@ func (p *parser) visitAndAppendStmt(stmts []js_ast.Stmt, stmt js_ast.Stmt) []js_
 			}
 			p.recordUsage(s.Arg)
 
-			// String-valued enums do not form a two-way map
-			if hasStringValue {
+			// Const-based and string-valued enums do not form a two-way map
+			if hasStringValue || s.IsConst {
 				valueExprs = append(valueExprs, assignTarget)
 			} else {
 				// "Enum[assignTarget] = 'Name'"
@@ -10969,7 +10969,7 @@ func (p *parser) visitAndAppendStmt(stmts []js_ast.Stmt, stmt js_ast.Stmt) []js_
 
 		// Wrap this enum definition in a closure
 		stmts = p.generateClosureForTypeScriptEnum(
-			stmts, stmt.Loc, s.IsExport, s.Name.Loc, s.Name.Ref, s.Arg, valueExprs, allValuesArePure)
+			stmts, stmt.Loc, s.IsConst, s.IsExport, s.Name.Loc, s.Name.Ref, s.Arg, valueExprs, allValuesArePure)
 		return stmts
 
 	case *js_ast.SNamespace:

internal/js_parser/ts_parser.go

@@ -1270,7 +1270,7 @@ func (p *parser) skipTypeScriptTypeStmt(opts parseStmtOpts) {
 	p.lexer.ExpectOrInsertSemicolon()
 }
 
-func (p *parser) parseTypeScriptEnumStmt(loc logger.Loc, opts parseStmtOpts) js_ast.Stmt {
+func (p *parser) parseTypeScriptEnumStmt(loc logger.Loc, opts parseStmtOpts, isConst bool) js_ast.Stmt {
 	p.lexer.Expect(js_lexer.TEnum)
 	nameLoc := p.lexer.Loc()
 	nameText := p.lexer.Identifier.String
@@ -1445,6 +1445,7 @@ func (p *parser) parseTypeScriptEnumStmt(loc logger.Loc, opts parseStmtOpts) js_
 		Name:     name,
 		Arg:      tsNamespace.ArgRef,
 		Values:   values,
+		IsConst:  isConst,
 		IsExport: opts.isExport,
 	}}
 }
@@ -1865,7 +1866,7 @@ func (p *parser) generateClosureForTypeScriptNamespaceOrEnum(
 }
 
 func (p *parser) generateClosureForTypeScriptEnum(
-	stmts []js_ast.Stmt, stmtLoc logger.Loc, isExport bool, nameLoc logger.Loc,
+	stmts []js_ast.Stmt, stmtLoc logger.Loc, isConst bool, isExport bool, nameLoc logger.Loc,
 	nameRef ast.Ref, argRef ast.Ref, exprsInsideClosure []js_ast.Expr,
 	allValuesArePure bool,
 ) []js_ast.Stmt {

internal/js_parser/ts_parser_test.go

@@ -1640,10 +1640,17 @@ bar = 0 /* FOO */;
 	expectPrintedTS(t, "(() => { const enum Foo { A } () => Foo.A })", `() => {
   let Foo;
   ((Foo) => {
-    Foo[Foo["A"] = 0] = "A";
+    Foo["A"] = 0;
   })(Foo || (Foo = {}));
   () => 0 /* A */;
 };
+`)
+
+	expectPrintedTS(t, "const enum Foo { A, B }", `var Foo = /* @__PURE__ */ ((Foo) => {
+  Foo["A"] = 0;
+  Foo["B"] = 1;
+  return Foo;
+})(Foo || {});
 `)
 }