From 780ebde69cd890c070a05f7b80a81249f30ec58c Mon Sep 17 00:00:00 2001
From: Rikki Gibson <rigibson@microsoft.com>
Date: Tue, 14 May 2024 16:06:13 -0700
Subject: [PATCH] fix

---
 .../Symbols/Source/SourceComplexParameterSymbol.cs     |  3 +--
 .../Symbols/Source/SourcePropertyAccessorSymbol.cs     |  9 ++++++++-
 .../SynthesizedAccessorValueParameterSymbol.cs         | 10 ++++------
 3 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceComplexParameterSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceComplexParameterSymbol.cs
index 1f182b73abc9b..e8a8c612f1210 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceComplexParameterSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceComplexParameterSymbol.cs
@@ -506,7 +506,7 @@ protected SourceParameterSymbol? PartialDefinitionPart
             }
         }
 
-        internal override SyntaxList<AttributeListSyntax> AttributeDeclarationList
+        internal sealed override SyntaxList<AttributeListSyntax> AttributeDeclarationList
         {
             get
             {
@@ -520,7 +520,6 @@ internal override SyntaxList<AttributeListSyntax> AttributeDeclarationList
         /// </summary>
         internal virtual OneOrMany<SyntaxList<AttributeListSyntax>> GetAttributeDeclarations()
         {
-            // TODO2: should this be non-virtual and subtypes override 'AttributeDeclarationList' instead?
             Debug.Assert(PartialImplementationPart is null);
             if (PartialDefinitionPart is { } definitionPart)
             {
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertyAccessorSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertyAccessorSymbol.cs
index acf4d7ab312d3..7460e057701c0 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertyAccessorSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertyAccessorSymbol.cs
@@ -631,12 +631,19 @@ public sealed override ImmutableArray<MethodSymbol> ExplicitInterfaceImplementat
 
         internal sealed override OneOrMany<SyntaxList<AttributeListSyntax>> GetAttributeDeclarations()
         {
-            Debug.Assert(PartialDefinitionPart is null);
             if (PartialImplementationPart is { } implementation)
             {
                 return OneOrMany.Create(AttributeDeclarationList, ((SourcePropertyAccessorSymbol)implementation).AttributeDeclarationList);
             }
 
+            // If we are asking this question on a partial implementation symbol,
+            // it must be from a context which prefers to order implementation attributes before definition attributes.
+            // For example, the 'value' parameter of a set accessor.
+            if (PartialDefinitionPart is { } definition)
+            {
+                return OneOrMany.Create(AttributeDeclarationList, ((SourcePropertyAccessorSymbol)definition).AttributeDeclarationList);
+            }
+
             return OneOrMany.Create(AttributeDeclarationList);
         }
 
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedAccessorValueParameterSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedAccessorValueParameterSymbol.cs
index bfe1cb85ababc..7252c0fee9068 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedAccessorValueParameterSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedAccessorValueParameterSymbol.cs
@@ -70,13 +70,11 @@ protected override IAttributeTargetSymbol AttributeOwner
             get { return (SourceMemberMethodSymbol)this.ContainingSymbol; }
         }
 
-        internal sealed override SyntaxList<AttributeListSyntax> AttributeDeclarationList
+        internal override OneOrMany<SyntaxList<AttributeListSyntax>> GetAttributeDeclarations()
         {
-            get
-            {
-                var accessor = (SourcePropertyAccessorSymbol)this.ContainingSymbol;
-                return accessor.AttributeDeclarationList;
-            }
+            // Bind the attributes on the accessor's attribute syntax list with "param" target specifier.
+            var accessor = (SourceMemberMethodSymbol)this.ContainingSymbol;
+            return accessor.GetAttributeDeclarations();
         }
 
         internal override void AddSynthesizedAttributes(PEModuleBuilder moduleBuilder, ref ArrayBuilder<SynthesizedAttributeData> attributes)