Handle nullable ValidateRange parameter types

Co-authored-by: bergmeister <9250262+bergmeister@users.noreply.github.com>

Author: Copilot

Rules/AvoidValidateRangeTypeMismatch.cs

@@ -68,6 +68,8 @@ public IEnumerable<DiagnosticRecord> AnalyzeScript(Ast ast, string fileName)
                     parameterType = parameterType.GetElementType();
                 }
 
+                parameterType = Nullable.GetUnderlyingType(parameterType) ?? parameterType;
+
                 if (!FloatingPointAndDecimalTypes.Contains(parameterType))
                 {
                     continue;

Tests/Rules/AvoidValidateRangeTypeMismatch.tests.ps1

@@ -44,6 +44,9 @@ namespace Contoso
             'function Test { param([double][ValidateRange(1, 2)]$Value) }'
             'function Test { param([single][ValidateRange(-1, 2)]$Value) }'
             'function Test { param([decimal][ValidateRange(1, 2)]$Value) }'
+            'function Test { param([Nullable[double]][ValidateRange(1, 2)]$Value) }'
+            'function Test { param([Nullable[single]][ValidateRange(1, 2)]$Value) }'
+            'function Test { param([Nullable[decimal]][ValidateRange(1, 2)]$Value) }'
             'function Test { param([double[]][ValidateRange(1, 2)]$Values) }'
             'function Test { param([double][System.Management.Automation.ValidateRangeAttribute(1, 2)]$Value) }'
             'function Test { param([double][ValidateRange([int]0.0, [int]100.0)]$Value) }'