only '++' and '--' unary operators can change exports

src/compiler/emitter.ts

@@ -2445,7 +2445,8 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, Promi
             }
 
             function emitPrefixUnaryExpression(node: PrefixUnaryExpression) {
-                const exportChanged = isNameOfExportedSourceLevelDeclarationInSystemExternalModule(node.operand);
+                const exportChanged = (node.operator === SyntaxKind.PlusPlusToken || node.operator === SyntaxKind.MinusMinusToken) &&
+                    isNameOfExportedSourceLevelDeclarationInSystemExternalModule(node.operand);
 
                 if (exportChanged) {
                     // emit

tests/baselines/reference/prefixUnaryOperatorsOnExportedVariables.js

@@ -0,0 +1,58 @@
+//// [prefixUnaryOperatorsOnExportedVariables.ts]
+
+export var x = false;
+export var y = 1;
+if (!x) {
+    
+}
+
+if (+x) {
+    
+}
+
+if (-x) {
+    
+}
+
+if (~x) {
+    
+}
+
+if (void x) {
+    
+}
+
+if (typeof x) {
+    
+}
+
+if (++y) {
+    
+}
+
+//// [prefixUnaryOperatorsOnExportedVariables.js]
+System.register([], function(exports_1) {
+    "use strict";
+    var x, y;
+    return {
+        setters:[],
+        execute: function() {
+            exports_1("x", x = false);
+            exports_1("y", y = 1);
+            if (!x) {
+            }
+            if (+x) {
+            }
+            if (-x) {
+            }
+            if (~x) {
+            }
+            if (void x) {
+            }
+            if (typeof x) {
+            }
+            if (exports_1("y", ++y)) {
+            }
+        }
+    }
+});

tests/baselines/reference/prefixUnaryOperatorsOnExportedVariables.symbols

@@ -0,0 +1,42 @@
+=== tests/cases/compiler/prefixUnaryOperatorsOnExportedVariables.ts ===
+
+export var x = false;
+>x : Symbol(x, Decl(prefixUnaryOperatorsOnExportedVariables.ts, 1, 10))
+
+export var y = 1;
+>y : Symbol(y, Decl(prefixUnaryOperatorsOnExportedVariables.ts, 2, 10))
+
+if (!x) {
+>x : Symbol(x, Decl(prefixUnaryOperatorsOnExportedVariables.ts, 1, 10))
+    
+}
+
+if (+x) {
+>x : Symbol(x, Decl(prefixUnaryOperatorsOnExportedVariables.ts, 1, 10))
+    
+}
+
+if (-x) {
+>x : Symbol(x, Decl(prefixUnaryOperatorsOnExportedVariables.ts, 1, 10))
+    
+}
+
+if (~x) {
+>x : Symbol(x, Decl(prefixUnaryOperatorsOnExportedVariables.ts, 1, 10))
+    
+}
+
+if (void x) {
+>x : Symbol(x, Decl(prefixUnaryOperatorsOnExportedVariables.ts, 1, 10))
+    
+}
+
+if (typeof x) {
+>x : Symbol(x, Decl(prefixUnaryOperatorsOnExportedVariables.ts, 1, 10))
+    
+}
+
+if (++y) {
+>y : Symbol(y, Decl(prefixUnaryOperatorsOnExportedVariables.ts, 2, 10))
+    
+}

tests/baselines/reference/prefixUnaryOperatorsOnExportedVariables.types

@@ -0,0 +1,51 @@
+=== tests/cases/compiler/prefixUnaryOperatorsOnExportedVariables.ts ===
+
+export var x = false;
+>x : boolean
+>false : boolean
+
+export var y = 1;
+>y : number
+>1 : number
+
+if (!x) {
+>!x : boolean
+>x : boolean
+    
+}
+
+if (+x) {
+>+x : number
+>x : boolean
+    
+}
+
+if (-x) {
+>-x : number
+>x : boolean
+    
+}
+
+if (~x) {
+>~x : number
+>x : boolean
+    
+}
+
+if (void x) {
+>void x : undefined
+>x : boolean
+    
+}
+
+if (typeof x) {
+>typeof x : string
+>x : boolean
+    
+}
+
+if (++y) {
+>++y : number
+>y : number
+    
+}

tests/cases/compiler/prefixUnaryOperatorsOnExportedVariables.ts

@@ -0,0 +1,32 @@
+// @target: ES5
+// @module: system
+
+export var x = false;
+export var y = 1;
+if (!x) {
+    
+}
+
+if (+x) {
+    
+}
+
+if (-x) {
+    
+}
+
+if (~x) {
+    
+}
+
+if (void x) {
+    
+}
+
+if (typeof x) {
+    
+}
+
+if (++y) {
+    
+}