simplify

src/Features/Core/Portable/EmbeddedLanguages/RegularExpressions/RegexLexer.cs

@@ -101,7 +101,7 @@ private ImmutableArray<RegexTrivia> ScanLeadingTrivia(bool allowTrivia, RegexOpt
                 return ImmutableArray<RegexTrivia>.Empty;
             }
 
-            var result = ArrayBuilder<RegexTrivia>.GetInstance();
+            using var _ = ArrayBuilder<RegexTrivia>.GetInstance(out var result);
 
             while (Position < Text.Length)
             {
@@ -122,7 +122,7 @@ private ImmutableArray<RegexTrivia> ScanLeadingTrivia(bool allowTrivia, RegexOpt
                 break;
             }
 
-            return result.ToImmutableAndFree();
+            return result.ToImmutable();
         }
 
         public RegexTrivia? ScanComment(RegexOptions options)

src/Features/Core/Portable/EmbeddedLanguages/RegularExpressions/RegexParser.cs

@@ -171,11 +171,11 @@ private RegexTree ParseTree()
             var root = new RegexCompilationUnit(expression, _currentToken);
 
             var seenDiagnostics = new HashSet<EmbeddedDiagnostic>();
-            var diagnostics = ArrayBuilder<EmbeddedDiagnostic>.GetInstance();
+            using var _ = ArrayBuilder<EmbeddedDiagnostic>.GetInstance(out var diagnostics);
             CollectDiagnostics(root, seenDiagnostics, diagnostics);
 
             return new RegexTree(
-                _lexer.Text, root, diagnostics.ToImmutableAndFree(),
+                _lexer.Text, root, diagnostics.ToImmutable(),
                 _captureNamesToSpan, _captureNumbersToSpan);
         }
 
@@ -259,7 +259,7 @@ private RegexExpressionNode ParseAlternatingSequencesWorker(bool consumeClosePar
 
         private RegexSequenceNode ParseSequence(bool consumeCloseParen)
         {
-            using var _ = ArrayBuilder<RegexExpressionNode>.GetInstance(out var builder);
+            using var _1 = ArrayBuilder<RegexExpressionNode>.GetInstance(out var builder);
             while (ShouldConsumeSequenceElement(consumeCloseParen))
             {
                 var last = builder.Count == 0 ? null : builder.Last();
@@ -269,10 +269,10 @@ private RegexSequenceNode ParseSequence(bool consumeCloseParen)
             // We wil commonly get tons of text nodes in a row.  For example, the
             // regex `abc` will be three text nodes in a row.  To help save on memory
             // try to merge that into one single text node.
-            var sequence = ArrayBuilder<RegexExpressionNode>.GetInstance();
+            using var _2 = ArrayBuilder<RegexExpressionNode>.GetInstance(out var sequence);
             MergeTextNodes(builder, sequence);
 
-            return new RegexSequenceNode(sequence.ToImmutableAndFree());
+            return new RegexSequenceNode(sequence.ToImmutable());
         }
 
         private static void MergeTextNodes(ArrayBuilder<RegexExpressionNode> list, ArrayBuilder<RegexExpressionNode> final)
@@ -1255,7 +1255,7 @@ private RegexBaseCharacterClassNode ParseCharacterClass()
             // We wil commonly get tons of text nodes in a row.  For example, the
             // regex `[abc]` will be three text nodes in a row.  To help save on memory
             // try to merge that into one single text node.
-            var contents = ArrayBuilder<RegexExpressionNode>.GetInstance();
+            using var _ = ArrayBuilder<RegexExpressionNode>.GetInstance(out var contents);
             MergeTextNodes(builder, contents);
 
             if (closeBracketToken.IsMissing)
@@ -1265,7 +1265,7 @@ private RegexBaseCharacterClassNode ParseCharacterClass()
                     GetTokenStartPositionSpan(_currentToken)));
             }
 
-            var components = new RegexSequenceNode(contents.ToImmutableAndFree());
+            var components = new RegexSequenceNode(contents.ToImmutable());
             return caretToken.IsMissing
                 ? (RegexBaseCharacterClassNode)new RegexCharacterClassNode(openBracketToken, components, closeBracketToken)
                 : new RegexNegatedCharacterClassNode(openBracketToken, caretToken, components, closeBracketToken);