fix(ast): Prevent post-increment ops on declared variables

miraleung · miraleung · commit f0efce14f212 · 2021-04-06T22:03:07.000-07:00
diff --git a/src/main/java/com/google/api/generator/engine/ast/UnaryOperationExpr.java b/src/main/java/com/google/api/generator/engine/ast/UnaryOperationExpr.java
@@ -73,15 +73,18 @@ private UnaryOperationExpr build() {
       TypeNode exprType = unaryOperationExpr.expr().type();
       OperatorKind operator = unaryOperationExpr.operatorKind();
 
-      // TODO: (summerji) Add Decl Check for variable.
       // Add final keyword checking for post/prefix ++, -- when needed.
       if (operator.equals(OperatorKind.UNARY_POST_INCREMENT)
           && unaryOperationExpr.expr() instanceof VariableExpr) {
+        VariableExpr varExpr = (VariableExpr) unaryOperationExpr.expr();
         Preconditions.checkState(
-            !((VariableExpr) unaryOperationExpr.expr()).isFinal(),
+            !varExpr.isFinal(),
+            String.format("Cannot increment the final variable '%s'.", varExpr.variable().name()));
+
+        Preconditions.checkState(
+            !varExpr.isDecl(),
             String.format(
-                "Cannot assign a value to final variable '%s'.",
-                ((VariableExpr) unaryOperationExpr.expr()).variable().name()));
+                "Cannot increment the declaration of variable %s", varExpr.variable().name()));
       }
 
       final String errorMsg =
diff --git a/src/test/java/com/google/api/generator/engine/ast/UnaryOperationExprTest.java b/src/test/java/com/google/api/generator/engine/ast/UnaryOperationExprTest.java
@@ -95,8 +95,19 @@ public void invalidPostIncrement_referenceType() {
 
   @Test
   public void invalidPostIncrement_finalVariable() {
-    Variable var = Variable.builder().setName("i").setType(TypeNode.INT).build();
-    VariableExpr variableExpr = VariableExpr.builder().setIsFinal(true).setVariable(var).build();
+    Variable variable = Variable.builder().setName("i").setType(TypeNode.INT).build();
+    VariableExpr variableExpr =
+        VariableExpr.builder().setIsFinal(true).setVariable(variable).build();
+    assertThrows(
+        IllegalStateException.class,
+        () -> UnaryOperationExpr.postfixIncrementWithExpr(variableExpr));
+  }
+
+  @Test
+  public void invalidPostIncrement_declaredVariable() {
+    Variable variable = Variable.builder().setName("i").setType(TypeNode.INT).build();
+    VariableExpr variableExpr =
+        VariableExpr.builder().setIsDecl(true).setVariable(variable).build();
     assertThrows(
         IllegalStateException.class,
         () -> UnaryOperationExpr.postfixIncrementWithExpr(variableExpr));
