(PowerShellGH-811) Fix folding for regions with same end token

Previously the token matching was broken;
```
foreach ($1 in $2) {     <----- STARTS MATCH HERE (1)

    $x = @{  <-----   STARTS MATCH HERE (2)
        'abc' = 'def'
    }        <----- ENDS   MATCH HERE (1) (2)
}
```

This was caused by two or more different token pairs sharing the same end token.
This commit modifies the token pair matching to take an array of Start Tokens
instead of a single.  This has the added benefit of performance increase too.

This commit also adds tests for this scenario.

src/PowerShellEditorServices/Language/TokenOperations.cs

@@ -3,6 +3,7 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 //
 
+using System;
 using System.Collections.Generic;
 using System.Management.Automation.Language;
 using System.Text.RegularExpressions;
@@ -28,24 +29,17 @@ internal static FoldingReference[] FoldableRegions(
         {
             List<FoldingReference> foldableRegions = new List<FoldingReference>();
 
-            // Find matching braces { -> }
-            foldableRegions.AddRange(
-                MatchTokenElements(tokens, TokenKind.LCurly, TokenKind.RCurly, RegionKindNone)
-            );
-
-            // Find matching braces ( -> )
-            foldableRegions.AddRange(
-                MatchTokenElements(tokens, TokenKind.LParen, TokenKind.RParen, RegionKindNone)
-            );
-
-            // Find matching arrays @( -> )
+            // Find matching braces  { -> }
+            // Find matching hashes @{ -> }
             foldableRegions.AddRange(
-                MatchTokenElements(tokens, TokenKind.AtParen, TokenKind.RParen, RegionKindNone)
+                MatchTokenElements(tokens, new TokenKind[] { TokenKind.LCurly, TokenKind.AtCurly }, TokenKind.RCurly, RegionKindNone)
             );
 
-            // Find matching hashes @{ -> }
+            // Find matching parentheses     ( -> )
+            // Find matching array literals @( -> )
+            // Find matching subexpressions $( -> )
             foldableRegions.AddRange(
-                MatchTokenElements(tokens, TokenKind.AtCurly, TokenKind.RParen, RegionKindNone)
+                MatchTokenElements(tokens, new TokenKind[] { TokenKind.LParen, TokenKind.AtParen, TokenKind.DollarParen }, TokenKind.RParen, RegionKindNone)
             );
 
             // Find contiguous here strings @' -> '@
@@ -146,19 +140,19 @@ static private FoldingReference CreateFoldingReference(
         }
 
         /// <summary>
-        /// Given an array of tokens, find matching regions which start and end with a different TokenKind
+        /// Given an array of tokens, find matching regions which start (array of tokens) and end with a different TokenKind
         /// </summary>
         static private List<FoldingReference> MatchTokenElements(
             Token[] tokens,
-            TokenKind startTokenKind,
+            TokenKind[] startTokenKind,
             TokenKind endTokenKind,
             string matchKind)
         {
             List<FoldingReference> result = new List<FoldingReference>();
             Stack<Token> tokenStack = new Stack<Token>();
             foreach (Token token in tokens)
             {
-                if (token.Kind == startTokenKind) {
+                if (Array.IndexOf(startTokenKind, token.Kind) != -1) {
                     tokenStack.Push(token);
                 }
                 if ((tokenStack.Count > 0) && (token.Kind == endTokenKind)) {

test/PowerShellEditorServices.Test/Language/TokenOperationsTests.cs

@@ -217,5 +217,33 @@ public void LaguageServiceFindsFoldablRegionsWithDuplicateRegions() {
             FoldingReference[] result = GetRegions(testString);
             AssertFoldingReferenceArrays(expectedFolds, result);
         }
+
+        // This tests that token matching { -> }, @{ -> } and
+        // ( -> ), @( -> ) and $( -> ) does not confuse the folder
+        [Fact]
+        public void LaguageServiceFindsFoldablRegionsWithSameEndToken() {
+            string testString =
+@"foreach ($1 in $2) {
+
+    $x = @{
+        'abc' = 'def'
+    }
+}
+
+$y = $(
+    $arr = @('1', '2'); Write-Host ($arr)
+)
+";
+            FoldingReference[] expectedFolds = {
+                CreateFoldingReference(0, 19, 4, 1, null),
+                CreateFoldingReference(2,  9, 3, 5, null),
+                CreateFoldingReference(7,  5, 8, 1, null)
+            };
+
+            FoldingReference[] result = GetRegions(testString);
+
+            AssertFoldingReferenceArrays(expectedFolds, result);
+        }
+
     }
 }