Make a variable assignment in a ParenExpression to return the variable value (PowerShell#17174)

Author: daxian-dbw

src/System.Management.Automation/engine/ShellVariable.cs

@@ -244,6 +244,14 @@ internal void DebuggerCheckVariableWrite()
             }
         }
 
+        /// <summary>
+        /// Gets the value without triggering debugger check.
+        /// </summary>
+        internal virtual object GetValueRaw()
+        {
+            return _value;
+        }
+
         /// <summary>
         /// Gets or sets the value of the variable.
         /// </summary>
@@ -796,6 +804,11 @@ public override object Value
             }
         }
 
+        internal override object GetValueRaw()
+        {
+            return _tuple.GetValue(_tupleSlot);
+        }
+
         internal override void SetValueRaw(object newValue, bool preserveValueTypeSemantics)
         {
             if (preserveValueTypeSemantics)

src/System.Management.Automation/engine/runtime/Operations/VariableOps.cs

@@ -46,6 +46,13 @@ internal static object SetVariableValue(VariablePath variablePath, object value,
                                      : GetAttributeCollection(attributeAsts);
                 var = new PSVariable(variablePath.UnqualifiedPath, value, ScopedItemOptions.None, attributes);
 
+                if (attributes.Count > 0)
+                {
+                    // When there are any attributes, it's possible the value was converted/transformed.
+                    // Use 'GetValueRaw' here so the debugger check won't be triggered.
+                    value = var.GetValueRaw();
+                }
+
                 // Marking untrusted values for assignments in 'ConstrainedLanguage' mode is done in
                 // SessionStateScope.SetVariable.
                 sessionState.SetVariable(variablePath, var, false, origin);
@@ -81,7 +88,7 @@ internal static object SetVariableValue(VariablePath variablePath, object value,
                             null,
                             Metadata.InvalidValueFailure,
                             var.Name,
-                            ((value != null) ? value.ToString() : "$null"));
+                            (value != null) ? value.ToString() : "$null");
 
                         throw e;
                     }

test/powershell/Language/Scripting/Scripting.Followup.Tests.ps1

@@ -29,4 +29,10 @@ Describe "Scripting.Followup.Tests" -Tags "CI" {
         ## $arraylist.Clear() should be executed
         $arraylist.Count | Should -Be 0
     }
+
+    ## fix https://github.com/PowerShell/PowerShell/issues/17165
+    It "([bool] `$var = 42) should return the varaible value" {
+        ([bool]$var = 42).GetType().FullName | Should -Be "System.Boolean"
+        . { ([bool]$var = 42).GetType().FullName } | Should -Be "System.Boolean"
+    }
 }