Reduce allocations from string.Split in PatternMatcher constructor

src/Features/Core/Shared/Utilities/PatternMatcher.cs

@@ -165,9 +165,19 @@ public PatternMatcher(string pattern, CultureInfo culture, bool verbatimIdentifi
             _compareInfo = culture.CompareInfo;
 
             _fullPatternSegment = new Segment(pattern, verbatimIdentifierPrefixIsWordCharacter);
+
+            if (pattern.IndexOf('.') < 0)
+            {
+                // PERF: Avoid string.Split allocations when the pattern doesn't contain a dot.
+                _dotSeparatedSegments = pattern.Length > 0 ? new Segment[1] { _fullPatternSegment } : SpecializedCollections.EmptyArray<Segment>();
+            }
+            else
+            {
                 _dotSeparatedSegments = pattern.Split(s_dotCharacterArray, StringSplitOptions.RemoveEmptyEntries)
                                                 .Select(text => new Segment(text.Trim(), verbatimIdentifierPrefixIsWordCharacter))
                                                 .ToArray();
+            }
+
             _invalidPattern = _dotSeparatedSegments.Length == 0 || _dotSeparatedSegments.Any(s => s.IsInvalid);
         }