publish exported postfix operators as 'E("", ++x) - 1' and 'E("", --x) + 1'

src/compiler/emitter.ts

@@ -1963,18 +1963,24 @@ var __param = this.__param || function(index, decorator) { return function (targ
             function emitPostfixUnaryExpression(node: PostfixUnaryExpression) {
                 const exportChanged = isNameOfExportedSourceLevelDeclarationInSystemExternalModule(node.operand);
                 if (exportChanged) {
-                    write(`${exportFunctionForFile}("`);
+                    // emit 'x++' as '(export('x', ++x) - 1)' and 'x--' as '(export('x', --x) + 1)'
+                    write(`(${exportFunctionForFile}("`);
                     emitNodeWithoutSourceMap(node.operand);
                     write(`", `);
+
+                    write(tokenToString(node.operator));
+                    emit(node.operand);
+
+                    if (node.operator === SyntaxKind.PlusPlusToken) {
+                        write(") - 1)");
+                    }
+                    else {
+                        write(") + 1)");
+                    }
                 }
-
-                emit(node.operand);
-                write(tokenToString(node.operator));
-
-                if (exportChanged) {
-                    write("), ");
-                    emitNodeWithoutSourceMap(node.operand);
-                    write(node.operator === SyntaxKind.PlusPlusToken ? " - 1" : " + 1");
+                else {
+                    emit(node.operand);
+                    write(tokenToString(node.operator));
                 }
             }
 

tests/baselines/reference/systemModule8.js

@@ -14,6 +14,8 @@ x |= 1;
 x &= 1;
 for (x = 5;;x++) {}
 for (x = 8;;x--) {}
+for (x = 15;;++x) {}
+for (x = 18;;--x) {}
 
 for (let x = 50;;) {}
 function foo() {
@@ -35,8 +37,8 @@ System.register([], function(exports_1) {
         execute: function() {
             exports_1("x", x);
             exports_1("x", x = 1);
-            exports_1("x", x++), x - 1;
-            exports_1("x", x--), x + 1;
+            (exports_1("x", ++x) - 1);
+            (exports_1("x", --x) + 1);
             exports_1("x", ++x);
             exports_1("x", --x);
             exports_1("x", x += 1);
@@ -45,8 +47,10 @@ System.register([], function(exports_1) {
             exports_1("x", x /= 1);
             exports_1("x", x |= 1);
             exports_1("x", x &= 1);
-            for (exports_1("x", x = 5);; exports_1("x", x++), x - 1) { }
-            for (exports_1("x", x = 8);; exports_1("x", x--), x + 1) { }
+            for (exports_1("x", x = 5);; (exports_1("x", ++x) - 1)) { }
+            for (exports_1("x", x = 8);; (exports_1("x", --x) + 1)) { }
+            for (exports_1("x", x = 15);; exports_1("x", ++x)) { }
+            for (exports_1("x", x = 18);; exports_1("x", --x)) { }
             for (x_1 = 50;;) { }
             exports_1("y", y = ([1])[0]);
             _a = { a: true, b: { c: "123" } }, exports_1("z0", z0 = _a.a), exports_1("z1", z1 = _a.b.c);

tests/baselines/reference/systemModule8.types

@@ -59,6 +59,18 @@ for (x = 8;;x--) {}
 >x-- : number
 >x : any
 
+for (x = 15;;++x) {}
+>x = 15 : number
+>x : any
+>++x : number
+>x : any
+
+for (x = 18;;--x) {}
+>x = 18 : number
+>x : any
+>--x : number
+>x : any
+
 for (let x = 50;;) {}
 >x : number
 

tests/cases/compiler/systemModule8.ts

@@ -14,6 +14,8 @@ x |= 1;
 x &= 1;
 for (x = 5;;x++) {}
 for (x = 8;;x--) {}
+for (x = 15;;++x) {}
+for (x = 18;;--x) {}
 
 for (let x = 50;;) {}
 function foo() {