Fix calculation for slot containing offset

Fixes issue dotnet#605 Add logic to not return zero-length nodes, since they never contain their offset.
mattwar · Feb 20, 2015 · 3799cae · 3799cae
1 parent 7b474cb
commit 3799cae
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Showing 2 changed files with 51 additions and 1 deletion.
diff --git a/src/Compilers/CSharp/Portable/Syntax/InternalSyntax/SyntaxList.WithLotsOfChildren.cs b/src/Compilers/CSharp/Portable/Syntax/InternalSyntax/SyntaxList.WithLotsOfChildren.cs
@@ -53,7 +53,19 @@ public override int FindSlotIndexContainingOffset(int offset)
             {
                 Debug.Assert(offset >= 0 && offset < FullWidth);
                 int idx = _childOffsets.BinarySearch(offset);
-                return idx >= 0 ? idx : (~idx - 1);
+
+                if (idx < 0)
+                {
+                    idx = (~idx - 1);
+                }
+
+                // skip zero-length nodes (they won't ever contain the offset)
+                while (idx < _childOffsets.Length - 1 && _childOffsets[idx] == _childOffsets[idx + 1])
+                {
+                    idx++;
+                }
+
+                return idx;
             }
 
             private static int[] CalculateOffsets(ArrayElement<CSharpSyntaxNode>[] children)

diff --git a/src/Compilers/CSharp/Test/Syntax/Syntax/SyntaxNodeTests.cs b/src/Compilers/CSharp/Test/Syntax/Syntax/SyntaxNodeTests.cs
@@ -481,6 +481,44 @@ public void TestFindToken()
             Assert.Equal(SyntaxKind.IfKeyword, token.Kind());
         }
 
+        [Fact]
+        public void TestFindTokenInLargeList()
+        {
+            var identifier = SyntaxFactory.Identifier("x");
+            var missingIdentifier = SyntaxFactory.MissingToken(SyntaxKind.IdentifierToken);
+            var name = SyntaxFactory.IdentifierName(identifier);
+            var missingName = SyntaxFactory.IdentifierName(missingIdentifier);
+            var comma = SyntaxFactory.Token(SyntaxKind.CommaToken);
+            var missingComma = SyntaxFactory.MissingToken(SyntaxKind.CommaToken);
+            var argument = SyntaxFactory.Argument(name);
+            var missingArgument = SyntaxFactory.Argument(missingName);
+
+            // make a large list that has lots of zero-length nodes (that shouldn't be found)
+            var nodesAndTokens = SyntaxFactory.NodeOrTokenList(
+                missingArgument, missingComma,
+                missingArgument, missingComma,
+                missingArgument, missingComma,
+                missingArgument, missingComma,
+                missingArgument, missingComma,
+                missingArgument, missingComma,
+                missingArgument, missingComma,
+                missingArgument, missingComma,
+                argument);
+
+            var argumentList = SyntaxFactory.ArgumentList(SyntaxFactory.SeparatedList<ArgumentSyntax>(SyntaxFactory.NodeOrTokenList(nodesAndTokens)));
+            var invocation = SyntaxFactory.InvocationExpression(name, argumentList);
+            CheckFindToken(invocation);
+        }
+
+        private void CheckFindToken(SyntaxNode node)
+        {
+            for (int i = node.FullSpan.End - 1; i >= 0; i--)
+            {
+                var token = node.FindToken(i);
+                Assert.Equal(true, token.FullSpan.Contains(i));
+            }
+        }
+
         [WorkItem(755236, "DevDiv")]
         [Fact]
         public void TestFindNode()