Disallow @Var on effectively final variables

PiperOrigin-RevId: 348082885
google · Dec 17, 2020 · b61a7df · b61a7df
1 parent a9e478a
commit b61a7df
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diff --git a/core/src/main/java/com/google/errorprone/bugpatterns/VarChecker.java b/core/src/main/java/com/google/errorprone/bugpatterns/VarChecker.java
@@ -17,6 +17,7 @@
 package com.google.errorprone.bugpatterns;
 
 import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.util.ASTHelpers.getAnnotationWithSimpleName;
 import static com.google.errorprone.util.ASTHelpers.isConsideredFinal;
 
 import com.google.errorprone.BugPattern;
@@ -32,6 +33,7 @@
 import com.sun.source.tree.Tree;
 import com.sun.source.tree.VariableTree;
 import com.sun.source.util.TreePath;
+import com.sun.tools.javac.code.Flags;
 import com.sun.tools.javac.code.Source;
 import com.sun.tools.javac.code.Symbol;
 import com.sun.tools.javac.tree.JCTree;
@@ -57,6 +59,14 @@ public Description matchVariable(VariableTree tree, VisitorState state) {
       return Description.NO_MATCH;
     }
     if (ASTHelpers.hasAnnotation(sym, Var.class, state)) {
+      if ((sym.flags() & Flags.EFFECTIVELY_FINAL) != 0) {
+        return buildDescription(tree)
+            .setMessage("@Var variable is never modified")
+            .addFix(
+                SuggestedFix.delete(
+                    getAnnotationWithSimpleName(tree.getModifiers().getAnnotations(), "Var")))
+            .build();
+      }
       return Description.NO_MATCH;
     }
     if (!ASTHelpers.getGeneratedBy(state).isEmpty()) {

diff --git a/core/src/test/java/com/google/errorprone/bugpatterns/VarCheckerTest.java b/core/src/test/java/com/google/errorprone/bugpatterns/VarCheckerTest.java
@@ -371,4 +371,22 @@ public void notSuppressedByUnrelatedSuppressWarningsAnnotation() {
             "}")
         .doTest();
   }
+
+  @Test
+  public void effectivelyFinal() {
+    compilationHelper
+        .addSourceLines(
+            "Test.java",
+            "import com.google.errorprone.annotations.Var;",
+            "class Test {",
+            "  int f(",
+            "      // BUG: Diagnostic contains: @Var variable is never modified",
+            "      @Var int x,",
+            "      @Var int y) {",
+            "    y++;",
+            "    return x + y;",
+            "  }",
+            "}")
+        .doTest();
+  }
 }