Use var in MustBeClosedChecker suggestions

Instead of writing out a specific type, we'll just use `var`. If we already have a declaration, e.g. replacing

  Foo f = foo();

with

  try (Foo f = foo()) { ... }

we still use the existing syntax (i.e., Foo, not var).

PiperOrigin-RevId: 472498888

core/src/main/java/com/google/errorprone/bugpatterns/AbstractMustBeClosedChecker.java

@@ -356,10 +356,6 @@ protected void addFix(
 
   private Optional<TryBlock> introduceSingleStatementTry(
       ExpressionTree tree, StatementTree stmt, VisitorState state) {
-    Type type = getType(tree);
-    if (type == null) {
-      return Optional.empty();
-    }
     SuggestedFix.Builder fix = SuggestedFix.builder();
     String name = suggestName(tree);
     if (state.getPath().getParentPath().getLeaf() instanceof ExpressionStatementTree) {
@@ -371,10 +367,7 @@ private Optional<TryBlock> introduceSingleStatementTry(
         new TryBlock(
             stmt,
             fix.prefixWith(
-                stmt,
-                String.format(
-                    "try (%s %s = %s) {",
-                    qualifyType(state, fix, type), name, state.getSourceForNode(tree)))));
+                stmt, String.format("try (var %s = %s) {", name, state.getSourceForNode(tree)))));
   }
 
   private Optional<TryBlock> extractToResourceInCurrentTry(
@@ -397,10 +390,6 @@ private Optional<TryBlock> extractToResourceInCurrentTry(
 
   private Optional<TryBlock> splitVariableDeclarationAroundTry(
       ExpressionTree tree, VariableTree var, VisitorState state) {
-    Type type = getType(tree);
-    if (type == null) {
-      return Optional.empty();
-    }
     int initPos = getStartPosition(var.getInitializer());
     int afterTypePos = state.getEndPosition(var.getType());
     String name = suggestName(tree);
@@ -412,12 +401,8 @@ private Optional<TryBlock> splitVariableDeclarationAroundTry(
                     afterTypePos,
                     initPos,
                     String.format(
-                        " %s;\ntry (%s %s = %s) {\n%s =",
-                        var.getName(),
-                        qualifyType(state, fix, type),
-                        name,
-                        state.getSourceForNode(tree),
-                        var.getName()))
+                        " %s;\ntry (var %s = %s) {\n%s =",
+                        var.getName(), name, state.getSourceForNode(tree), var.getName()))
                 .replace(tree, name)));
   }
 
@@ -436,7 +421,7 @@ private Optional<TryBlock> wrapTryFinallyAroundVariableScope(
                     String.format(
                         "try (%s %s = %s) {",
                         state.getSourceForNode(decl.getType()),
-                        decl.getName().toString(),
+                        decl.getName(),
                         state.getSourceForNode(decl.getInitializer())))
                 .delete(decl)));
   }

core/src/test/java/com/google/errorprone/bugpatterns/testdata/MustBeClosedCheckerPositiveCases_expected.java

@@ -53,7 +53,7 @@ Closeable mustBeClosedAnnotatedMethod() {
 
     void sameClass() {
       // BUG: Diagnostic contains:
-      try (Closeable closeable = mustBeClosedAnnotatedMethod()) {}
+      try (var closeable = mustBeClosedAnnotatedMethod()) {}
     }
   }
 
@@ -64,14 +64,13 @@ class MustBeClosedAnnotatedConstructor extends Closeable {
 
     void sameClass() {
       // BUG: Diagnostic contains:
-      try (MustBeClosedAnnotatedConstructor mustBeClosedAnnotatedConstructor =
-          new MustBeClosedAnnotatedConstructor()) {}
+      try (var mustBeClosedAnnotatedConstructor = new MustBeClosedAnnotatedConstructor()) {}
     }
   }
 
   void positiveCase1() {
     // BUG: Diagnostic contains:
-    try (Closeable closeable = new Foo().mustBeClosedAnnotatedMethod()) {}
+    try (var closeable = new Foo().mustBeClosedAnnotatedMethod()) {}
   }
 
   void positiveCase2() {
@@ -82,22 +81,21 @@ void positiveCase2() {
   void positiveCase3() {
     try {
       // BUG: Diagnostic contains:
-      try (Closeable closeable = new Foo().mustBeClosedAnnotatedMethod()) {}
+      try (var closeable = new Foo().mustBeClosedAnnotatedMethod()) {}
     } finally {
     }
   }
 
   void positiveCase4() {
     try (Closeable c = new Foo().mustBeClosedAnnotatedMethod()) {
       // BUG: Diagnostic contains:
-      try (Closeable closeable = new Foo().mustBeClosedAnnotatedMethod()) {}
+      try (var closeable = new Foo().mustBeClosedAnnotatedMethod()) {}
     }
   }
 
   void positiveCase5() {
     // BUG: Diagnostic contains:
-    try (MustBeClosedAnnotatedConstructor mustBeClosedAnnotatedConstructor =
-        new MustBeClosedAnnotatedConstructor()) {}
+    try (var mustBeClosedAnnotatedConstructor = new MustBeClosedAnnotatedConstructor()) {}
   }
 
   @MustBeClosed
@@ -152,23 +150,23 @@ public Closeable mustBeClosedAnnotatedMethod() {
 
   void subexpression() {
     // BUG: Diagnostic contains:
-    try (Closeable closeable = new Foo().mustBeClosedAnnotatedMethod()) {
+    try (var closeable = new Foo().mustBeClosedAnnotatedMethod()) {
       closeable.method();
     }
   }
 
   void ternary(boolean condition) {
     // BUG: Diagnostic contains:
     int result;
-    try (Closeable closeable = new Foo().mustBeClosedAnnotatedMethod()) {
+    try (var closeable = new Foo().mustBeClosedAnnotatedMethod()) {
       result = condition ? closeable.method() : 0;
     }
   }
 
   int variableDeclaration() {
     // BUG: Diagnostic contains:
     int result;
-    try (Closeable closeable = new Foo().mustBeClosedAnnotatedMethod()) {
+    try (var closeable = new Foo().mustBeClosedAnnotatedMethod()) {
       result = closeable.method();
     }
     return result;
@@ -182,7 +180,7 @@ void forLoopInitialization() {
   void forLoopConditionUnfixable() {
     // TODO(b/236715080): suggested fix changes behavior.
     // BUG: Diagnostic contains:
-    try (final Closeable closeable = new Foo().mustBeClosedAnnotatedMethod()) {
+    try (final var closeable = new Foo().mustBeClosedAnnotatedMethod()) {
       for (int i = 0; i < closeable.method(); ++i) {}
     }
   }