From 7ee554fa6480d90e650cc234d0a4a63dbce1dbf2 Mon Sep 17 00:00:00 2001
From: ghm <ghm@google.com>
Date: Tue, 26 Nov 2024 09:57:09 -0800
Subject: [PATCH] Use a single-letter name for primitives so there's a hope of
 it compiling.

PiperOrigin-RevId: 700375854
---
 .../PatternMatchingInstanceof.java            | 13 +++++++-
 .../PatternMatchingInstanceofTest.java        | 30 +++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/com/google/errorprone/bugpatterns/PatternMatchingInstanceof.java b/core/src/main/java/com/google/errorprone/bugpatterns/PatternMatchingInstanceof.java
index f58f3ea7bbb..63fddff29ae 100644
--- a/core/src/main/java/com/google/errorprone/bugpatterns/PatternMatchingInstanceof.java
+++ b/core/src/main/java/com/google/errorprone/bugpatterns/PatternMatchingInstanceof.java
@@ -23,6 +23,7 @@
 import static com.google.errorprone.util.ASTHelpers.getType;
 import static com.google.errorprone.util.SourceVersion.supportsPatternMatchingInstanceof;
 
+import com.google.common.base.Ascii;
 import com.google.common.collect.ImmutableSet;
 import com.google.errorprone.BugPattern;
 import com.google.errorprone.VisitorState;
@@ -41,6 +42,7 @@
 import com.sun.source.util.TreePathScanner;
 import com.sun.tools.javac.code.Symbol.VarSymbol;
 import com.sun.tools.javac.code.Type;
+import com.sun.tools.javac.code.TypeTag;
 import org.jspecify.annotations.Nullable;
 
 /** A BugPattern; see the summary. */
@@ -66,7 +68,16 @@ public Description matchInstanceOf(InstanceOfTree instanceOfTree, VisitorState s
         if (!allCasts.isEmpty()) {
           // This is a gamble as to an appropriate name. We could make sure it doesn't clash with
           // anything in scope, but that's effort.
-          var name = lowerFirstLetter(targetType.tsym.getSimpleName().toString());
+          String name;
+          var unboxed = state.getTypes().unboxedType(targetType);
+          if (targetType.isPrimitive() || (unboxed != null && unboxed.getTag() != TypeTag.NONE)) {
+            name =
+                String.valueOf(
+                    Ascii.toLowerCase(targetType.tsym.getSimpleName().toString().charAt(0)));
+          } else {
+            name = lowerFirstLetter(targetType.tsym.getSimpleName().toString());
+          }
+
           return describeMatch(
               instanceOfTree,
               SuggestedFix.builder()
diff --git a/core/src/test/java/com/google/errorprone/bugpatterns/PatternMatchingInstanceofTest.java b/core/src/test/java/com/google/errorprone/bugpatterns/PatternMatchingInstanceofTest.java
index 422d7e30f34..63068b1b7e4 100644
--- a/core/src/test/java/com/google/errorprone/bugpatterns/PatternMatchingInstanceofTest.java
+++ b/core/src/test/java/com/google/errorprone/bugpatterns/PatternMatchingInstanceofTest.java
@@ -212,6 +212,36 @@ void test(Object o) {
         .doTest();
   }
 
+  @Test
+  public void primitiveType_shortNameChosen() {
+    helper
+        .addInputLines(
+            "Test.java",
+            """
+            class Test {
+              void test(Object o) {
+                if (o instanceof Long) {
+                  test((Long) o);
+                  test(((Long) o).hashCode());
+                }
+              }
+            }
+            """)
+        .addOutputLines(
+            "Test.java",
+            """
+            class Test {
+              void test(Object o) {
+                if (o instanceof Long l) {
+                  test(l);
+                  test(l.hashCode());
+                }
+              }
+            }
+            """)
+        .doTest();
+  }
+
   @Test
   public void genericWithUpperBoundedWildcard() {
     helper