From afe99fcaea4c3df7c68cd00529890e29c88a2961 Mon Sep 17 00:00:00 2001
From: "Mathias R. Jessen" <IISResetMe@users.noreply.github.com>
Date: Tue, 17 May 2022 18:54:26 +0200
Subject: [PATCH] SemanticChecks: Avoid repeated type resolution of `[ordered]`
 (#17328)

---
 .../engine/parser/SemanticChecks.cs           |  7 +++++
 .../Scripting/Scripting.Followup.Tests.ps1    | 27 +++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/src/System.Management.Automation/engine/parser/SemanticChecks.cs b/src/System.Management.Automation/engine/parser/SemanticChecks.cs
index b792530193..2e2dcadd64 100644
--- a/src/System.Management.Automation/engine/parser/SemanticChecks.cs
+++ b/src/System.Management.Automation/engine/parser/SemanticChecks.cs
@@ -920,6 +920,13 @@ namespace System.Management.Automation.Language
                         ParserStrings.OrderedAttributeOnlyOnHashLiteralNode,
                         convertExpressionAst.Type.TypeName.FullName);
                 }
+
+                // Currently, the type name '[ordered]' is handled specially in PowerShell.
+                // When used in a conversion expression, it's only allowed on a hashliteral node, and it's
+                // always interpreted as an initializer for a case-insensitive
+                // 'System.Collections.Specialized.OrderedDictionary' by the compiler.
+                // So, we can return early from here.
+                return AstVisitAction.Continue;
             }
 
             if (typeof(PSReference) == convertExpressionAst.Type.TypeName.GetReflectionType())
diff --git a/test/powershell/Language/Scripting/Scripting.Followup.Tests.ps1 b/test/powershell/Language/Scripting/Scripting.Followup.Tests.ps1
index 9a691fa20d..933c53de6d 100644
--- a/test/powershell/Language/Scripting/Scripting.Followup.Tests.ps1
+++ b/test/powershell/Language/Scripting/Scripting.Followup.Tests.ps1
@@ -41,4 +41,31 @@ Describe "Scripting.Followup.Tests" -Tags "CI" {
         $obj.ForEach('p', 32) | Should -BeNullOrEmpty
         $obj.p | Should -Be 32
     }
+
+    It "Test the special type name 'ordered'" {
+        class ordered {
+            [hashtable] $Member
+            ordered([hashtable] $hash) {
+                $this.Member = $hash
+            }
+        }
+
+        ## `<expr> -as\-is [ordered]` resolves 'ordered' as a normal type name.
+        $hash = @{ key = 2 }
+        $result = $hash -as [ordered]
+        $result.GetType().FullName | Should -BeExactly ([ordered].FullName)
+        $result -is [ordered] | Should -BeTrue
+        $result.Member['key'] | Should -Be 2
+        $result.Member.Count | Should -Be 1
+
+        ## `[ordered]$hash` causes parsing error.
+        $err = $null
+        $null = [System.Management.Automation.Language.Parser]::ParseInput('[ordered]$hash', [ref]$null, [ref]$err)
+        $err.Count | Should -Be 1
+        $err[0].ErrorId | Should -BeExactly 'OrderedAttributeOnlyOnHashLiteralNode'
+
+        ## `[ordered]@{ key = 1 }` creates 'OrderedDictionary'
+        $result = [ordered]@{ key = 1 }
+        $result | Should -BeOfType 'System.Collections.Specialized.OrderedDictionary'
+    }
 }