Fix one of the classic blunders in UnnecessaryStringBuilder

`VariableTree#getType` doesn't have a position for variables with inferred types. PiperOrigin-RevId: 540607208
google · Jun 15, 2023 · 12b90df · 12b90df
1 parent a86e28b
commit 12b90df
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Showing 2 changed files with 30 additions and 6 deletions.
diff --git a/core/src/main/java/com/google/errorprone/bugpatterns/UnnecessaryStringBuilder.java b/core/src/main/java/com/google/errorprone/bugpatterns/UnnecessaryStringBuilder.java
@@ -47,6 +47,7 @@
 import com.sun.source.util.TreePathScanner;
 import com.sun.tools.javac.code.Symbol;
 import com.sun.tools.javac.code.Type;
+import com.sun.tools.javac.util.Position;
 import java.util.ArrayList;
 import java.util.List;
 import javax.lang.model.element.ElementKind;
@@ -124,12 +125,13 @@ public Description matchNewClass(NewClassTree tree, VisitorState state) {
     if (leaf instanceof VariableTree) {
       VariableTree variableTree = (VariableTree) leaf;
       if (isRewritableVariable(variableTree, state)) {
-        return describeMatch(
-            variableTree,
-            SuggestedFix.builder()
-                .replace(variableTree.getType(), "String")
-                .replace(variableTree.getInitializer(), replacement(state, parts))
-                .build());
+        SuggestedFix.Builder fix = SuggestedFix.builder();
+        if (state.getEndPosition(variableTree.getType()) != Position.NOPOS) {
+          // If the variable is declared with `var`, there's no declaration type to change
+          fix.replace(variableTree.getType(), "String");
+        }
+        fix.replace(variableTree.getInitializer(), replacement(state, parts));
+        return describeMatch(variableTree, fix.build());
       }
     }
     return NO_MATCH;

diff --git a/core/src/test/java/com/google/errorprone/bugpatterns/UnnecessaryStringBuilderTest.java b/core/src/test/java/com/google/errorprone/bugpatterns/UnnecessaryStringBuilderTest.java
@@ -142,4 +142,26 @@ public void needsParens() {
             "}")
         .doTest();
   }
+
+  @Test
+  public void varType() {
+    refactoringHelper
+        .addInputLines(
+            "Test.java",
+            "abstract class Test {",
+            "  void f() {",
+            "    var sb = new StringBuilder().append(\"hello\");",
+            "    System.err.println(sb);",
+            "  }",
+            "}")
+        .addOutputLines(
+            "Test.java",
+            "abstract class Test {",
+            "  void f() {",
+            "    var sb = \"hello\";",
+            "    System.err.println(sb);",
+            "  }",
+            "}")
+        .doTest();
+  }
 }