From 5ccbb97ae3f575732b0a3ba3e9a61b2317c57005 Mon Sep 17 00:00:00 2001
From: MartinGC94 <42123497+MartinGC94@users.noreply.github.com>
Date: Mon, 25 Jul 2022 20:15:19 +0200
Subject: [PATCH] Fix type inference for `ICollection` (#17752)

---
 .../engine/parser/TypeInferenceVisitor.cs                   | 3 ++-
 test/powershell/engine/Api/TypeInference.Tests.ps1          | 6 ++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/System.Management.Automation/engine/parser/TypeInferenceVisitor.cs b/src/System.Management.Automation/engine/parser/TypeInferenceVisitor.cs
index 363ce3536d..3ace7fb3a0 100644
--- a/src/System.Management.Automation/engine/parser/TypeInferenceVisitor.cs
+++ b/src/System.Management.Automation/engine/parser/TypeInferenceVisitor.cs
@@ -2443,9 +2443,10 @@ namespace System.Management.Automation
             foreach (var m in type.GetMethods(BindingFlags.Public | BindingFlags.Instance))
             {
                 var name = m.Name;
+                // Equals without string allocation
                 if (name.Length == propertyName.Length + 4
                     && name.StartsWith("get_")
-                    && propertyName.IndexOf(name, 4, StringComparison.Ordinal) == 4)
+                    && name.IndexOf(propertyName, 4, StringComparison.Ordinal) == 4)
                 {
                     res.Add(m);
                 }
diff --git a/test/powershell/engine/Api/TypeInference.Tests.ps1 b/test/powershell/engine/Api/TypeInference.Tests.ps1
index b5f2f64567..fbcc784570 100644
--- a/test/powershell/engine/Api/TypeInference.Tests.ps1
+++ b/test/powershell/engine/Api/TypeInference.Tests.ps1
@@ -1251,6 +1251,12 @@ Describe "Type inference Tests" -tags "CI" {
         $res.Count | Should -Be 1
         $res.Name | Should -Be 'System.Int32[]'
     }
+
+    It 'Infers type of index item in an ICollection' -Skip:(!$IsWindows) {
+        $res = [AstTypeInference]::InferTypeOf( { (Get-Acl -Path C:\).Access[0] }.Ast)
+        $res.Count | Should -Be 1
+        $res.Name | Should -Be 'System.Security.AccessControl.AuthorizationRule'
+    }
 }
 
 Describe "AstTypeInference tests" -Tags CI {