From 57ad3cce6ed76f58f9925da02a59fc2dc2b7f31c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alexei=20Eleusis=20D=C3=ADaz=20Vera?=
 <alexei.eleusis@gmail.com>
Date: Tue, 7 Mar 2017 09:26:16 -0800
Subject: [PATCH] invariant_boolean: When searching for references reassignment
 include PostfixExpression and similar, e.g. variable++.

Fixes https://github.com/dart-lang/linter/issues/337
---
 lib/src/rules/invariant_booleans.dart | 32 +++++++++++-----
 test/rules/invariant_booleans.dart    | 53 +++++++++++++++++++++++++++
 2 files changed, 76 insertions(+), 9 deletions(-)

diff --git a/lib/src/rules/invariant_booleans.dart b/lib/src/rules/invariant_booleans.dart
index ce8a29431..15a8473d0 100644
--- a/lib/src/rules/invariant_booleans.dart
+++ b/lib/src/rules/invariant_booleans.dart
@@ -216,15 +216,29 @@ AstNodePredicate _isConditionalStatementWithReturn(
 AstNodePredicate _noFurtherAssignmentInvalidatingCondition(
     Expression node, Iterable<AstNode> nodesInDFS) {
   Set<Identifier> identifiers = _findStatementIdentifiers(node.parent);
-  return (AstNode statement) =>
-      nodesInDFS
-          .skipWhile((n) => n != statement)
-          .takeWhile((n) => n != node)
-          .where((n) =>
-              n is AssignmentExpression &&
-              !identifiers.contains(n.leftHandSide))
-          .length ==
-      0;
+  return (AstNode statement) {
+    bool isMutation(AstNode n) {
+      if (n is AssignmentExpression) {
+        return !identifiers.contains(n.leftHandSide);
+      } else if (n is PostfixExpression) {
+        TokenType type = n.operator.type;
+        return (type == TokenType.PLUS_PLUS || type == TokenType.MINUS_MINUS) &&
+            !identifiers.contains(n.operand);
+      } else if (n is PrefixExpression) {
+        TokenType type = n.operator.type;
+        return (type == TokenType.PLUS_PLUS || type == TokenType.MINUS_MINUS) &&
+            !identifiers.contains(n.operand);
+      }
+
+      return false;
+    }
+
+    return nodesInDFS
+            .skipWhile((n) => n != statement)
+            .takeWhile((n) => n != node)
+            .where(isMutation)
+            .isEmpty;
+  };
 }
 
 List<Expression> _splitConjunctions(Expression expression) {
diff --git a/test/rules/invariant_booleans.dart b/test/rules/invariant_booleans.dart
index b0cf3e3f1..d521f21e8 100644
--- a/test/rules/invariant_booleans.dart
+++ b/test/rules/invariant_booleans.dart
@@ -237,3 +237,56 @@ void bug372(bool foo) {
     // doSomethingElse();
   }
 }
+
+void bug337_1(int offset, int length) {
+  if (offset >= length) {
+    return;
+  }
+
+  offset++;
+  if (offset >= length) { // OK
+  }
+}
+
+void bug337_2(int offset, int length) {
+  if (offset >= length) {
+    return;
+  }
+
+  offset--;
+  if (offset >= length) { // OK
+  }
+}
+
+void bug337_3(int offset, int length) {
+  if (offset >= length) {
+    return;
+  }
+
+  ++offset;
+  if (offset >= length) { // OK
+  }
+}
+
+void bug337_4(int offset, int length) {
+  if (offset >= length) {
+    return;
+  }
+
+  --offset;
+  if (offset >= length) { // OK
+  }
+}
+
+void test337_5() {
+  int b = 2;
+  if (b > 0) {
+    b--;
+    if (b == 0) {
+      return;
+    }
+    if (b > 0) {
+      return;
+    }
+  }
+}