Change GetParametersNoCopy to GetParametersAsSpan and use it in a few more places (#92310)

* Change GetParametersNoCopy to GetParametersAsSpan and use it  in a few more places

The internal GetParametersNoCopy avoids a defensive ParameterInfo[] copy, but it requires the callers to promise not to mutate the array. I'm changing the method to return a `ReadOnlySpan<ParameterInfo>`, which means a caller can't mutate it without using unsafe code, and enabling the compiler to flag any misuse.  I've then used it in a few more places. We might subsequently want to consider exposing it publicly.

* Update src/libraries/Common/src/System/Runtime/InteropServices/ComEventsMethod.cs

Author: stephentoub

src/coreclr/System.Private.CoreLib/src/Internal/Runtime/InteropServices/ComActivator.cs

@@ -201,7 +201,7 @@ private static void ClassRegistrationScenarioForType(ComActivationContext cxt, b
                     }
 
                     // Finally validate signature
-                    ParameterInfo[] methParams = method.GetParameters();
+                    ReadOnlySpan<ParameterInfo> methParams = method.GetParametersAsSpan();
                     if (method.ReturnType != typeof(void)
                         || methParams == null
                         || methParams.Length != 1

src/coreclr/System.Private.CoreLib/src/System/Attribute.CoreCLR.cs

@@ -227,8 +227,7 @@ private static bool InternalIsDefined(EventInfo element, Type attributeType, boo
                     }
                     else
                     {
-                        ParameterInfo[] parameters = rtMethod.GetParameters();
-                        return parameters[position]; // Point to the correct ParameterInfo of the method
+                        return rtMethod.GetParametersAsSpan()[position]; // Point to the correct ParameterInfo of the method
                     }
                 }
             }

src/coreclr/System.Private.CoreLib/src/System/Delegate.CoreCLR.cs

@@ -200,7 +200,7 @@ protected virtual MethodInfo GetMethodImpl()
                         {
                             // it's an open one, need to fetch the first arg of the instantiation
                             MethodInfo invoke = this.GetType().GetMethod("Invoke")!;
-                            declaringType = (RuntimeType)invoke.GetParameters()[0].ParameterType;
+                            declaringType = (RuntimeType)invoke.GetParametersAsSpan()[0].ParameterType;
                         }
                     }
                 }

src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/DynamicILGenerator.cs

@@ -94,7 +94,7 @@ public override void Emit(OpCode opcode, MethodInfo meth)
             }
             if (opcode.StackBehaviourPop == StackBehaviour.Varpop)
             {
-                stackchange -= meth.GetParametersNoCopy().Length;
+                stackchange -= meth.GetParametersAsSpan().Length;
             }
             // Pop the "this" parameter if the method is non-static,
             //  and the instruction is not newobj/ldtoken/ldftn.
@@ -416,7 +416,7 @@ private int GetMemberRefToken(MethodInfo methodInfo, Type[]? optionalParameterTy
             if (rtMeth == null && dm == null)
                 throw new ArgumentException(SR.Argument_MustBeRuntimeMethodInfo, nameof(methodInfo));
 
-            ParameterInfo[] paramInfo = methodInfo.GetParametersNoCopy();
+            ReadOnlySpan<ParameterInfo> paramInfo = methodInfo.GetParametersAsSpan();
             if (paramInfo != null && paramInfo.Length != 0)
             {
                 parameterTypes = new Type[paramInfo.Length];

src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/RuntimeModuleBuilder.cs

@@ -458,7 +458,7 @@ internal SignatureHelper GetMemberRefSignature(MethodBase? method, int cGenericP
             }
 
             Debug.Assert(method is RuntimeMethodInfo || method is RuntimeConstructorInfo);
-            ParameterInfo[] parameters = method.GetParametersNoCopy();
+            ReadOnlySpan<ParameterInfo> parameters = method.GetParametersAsSpan();
 
             Type[] parameterTypes = new Type[parameters.Length];
             Type[][] requiredCustomModifiers = new Type[parameterTypes.Length][];

src/coreclr/System.Private.CoreLib/src/System/Reflection/MethodBase.CoreCLR.cs

@@ -47,7 +47,7 @@ public abstract partial class MethodBase : MemberInfo
         // used by EE
         private IntPtr GetMethodDesc() { return MethodHandle.Value; }
 
-        internal virtual ParameterInfo[] GetParametersNoCopy() { return GetParameters(); }
+        internal virtual ReadOnlySpan<ParameterInfo> GetParametersAsSpan() { return GetParameters(); }
         #endregion
     }
 }

src/coreclr/System.Private.CoreLib/src/System/Reflection/RuntimeConstructorInfo.CoreCLR.cs

@@ -180,20 +180,11 @@ public override IList<CustomAttributeData> GetCustomAttributesData()
         // This seems to always returns System.Void.
         internal override Type GetReturnType() { return Signature.ReturnType; }
 
-        internal override ParameterInfo[] GetParametersNoCopy() =>
+        internal override ReadOnlySpan<ParameterInfo> GetParametersAsSpan() =>
             m_parameters ??= RuntimeParameterInfo.GetParameters(this, this, Signature);
 
-        public override ParameterInfo[] GetParameters()
-        {
-            ParameterInfo[] parameters = GetParametersNoCopy();
-
-            if (parameters.Length == 0)
-                return parameters;
-
-            ParameterInfo[] ret = new ParameterInfo[parameters.Length];
-            Array.Copy(parameters, ret, parameters.Length);
-            return ret;
-        }
+        public override ParameterInfo[] GetParameters() =>
+            GetParametersAsSpan().ToArray();
 
         public override MethodImplAttributes GetMethodImplementationFlags()
         {

src/coreclr/System.Private.CoreLib/src/System/Reflection/RuntimeCustomAttributeData.cs

@@ -278,7 +278,7 @@ private RuntimeCustomAttributeData(RuntimeModule scope, MetadataToken caCtorToke
                 m_ctor = (RuntimeConstructorInfo)scope.ResolveMethod(caCtorToken, attributeType.GenericTypeArguments, null)!.MethodHandle.GetMethodInfo();
             }
 
-            ParameterInfo[] parameters = m_ctor.GetParametersNoCopy();
+            ReadOnlySpan<ParameterInfo> parameters = m_ctor.GetParametersAsSpan();
             if (parameters.Length != 0)
             {
                 m_ctorParams = new CustomAttributeCtorParameter[parameters.Length];
@@ -412,7 +412,7 @@ private void Init(object pca)
             // Ensure there is only a single constructor for 'pca', so it is safe to suppress IL2075
             ConstructorInfo[] allCtors = type.GetConstructors(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
             Debug.Assert(allCtors.Length == 1);
-            Debug.Assert(allCtors[0].GetParameters().Length == 0);
+            Debug.Assert(allCtors[0].GetParametersAsSpan().Length == 0);
 #endif
 
             m_ctor = type.GetConstructors(BindingFlags.Public | BindingFlags.Instance)[0];

src/coreclr/System.Private.CoreLib/src/System/Reflection/RuntimeEventInfo.cs

@@ -63,10 +63,14 @@ o is RuntimeEventInfo m &&
         #region Object Overrides
         public override string ToString()
         {
-            if (m_addMethod == null || m_addMethod.GetParametersNoCopy().Length == 0)
+            ReadOnlySpan<ParameterInfo> parameters;
+            if (m_addMethod == null ||
+                (parameters = m_addMethod.GetParametersAsSpan()).Length == 0)
+            {
                 throw new InvalidOperationException(SR.InvalidOperation_NoPublicAddMethod);
+            }
 
-            return m_addMethod.GetParametersNoCopy()[0].ParameterType.FormatTypeName() + " " + Name;
+            return parameters[0].ParameterType.FormatTypeName() + " " + Name;
         }
 
         public override bool Equals(object? obj) =>

src/coreclr/System.Private.CoreLib/src/System/Reflection/RuntimeMethodInfo.CoreCLR.cs

@@ -240,7 +240,7 @@ public override Type? ReflectedType
         #endregion
 
         #region MethodBase Overrides
-        internal override ParameterInfo[] GetParametersNoCopy() =>
+        internal override ReadOnlySpan<ParameterInfo> GetParametersAsSpan() =>
             FetchNonReturnParameters();
 
         public override ParameterInfo[] GetParameters()