Fix crash when converting primary constructor to normal constructor

src/Features/CSharp/Portable/ConvertPrimaryToRegularConstructor/ConvertPrimaryToRegularConstructorCodeRefactoringProvider.cs

@@ -349,6 +349,9 @@ void AddConstructorDeclaration()
 
         async Task RewritePrimaryConstructorParameterReferencesAsync()
         {
+            using var _ = PooledHashSet<EqualsValueClauseSyntax>.GetInstance(out var removedInitializers);
+            removedInitializers.AddRange(initializedFieldsAndProperties.Select(t => t.initializer));
+
             foreach (var (parameter, references) in parameterReferences)
             {
                 // Only have to update references if we're synthesizing a field for this parameter.
@@ -364,6 +367,12 @@ async Task RewritePrimaryConstructorParameterReferencesAsync()
 
                     foreach (var identifierName in grouping)
                     {
+                        // Don't both updating an identifier that was in a node we already decided to explicitly remove.  For
+                        // example, if we have `int Prop { get; } = p;` and we already deleted `= p`, then no need to update
+                        // the `p` reference here.
+                        if (identifierName.GetAncestors<EqualsValueClauseSyntax>().Any(removedInitializers.Contains))
+                            continue;
+
                         var xmlElement = identifierName.AncestorsAndSelf().OfType<XmlEmptyElementSyntax>().FirstOrDefault();
                         if (xmlElement is { Name.LocalName.ValueText: "paramref" })
                         {

src/Features/CSharpTest/ConvertPrimaryToRegularConstructor/ConvertPrimaryToRegularConstructorTests.cs

@@ -2757,4 +2757,49 @@ public void Goo() { }
             LanguageVersion = LanguageVersionExtensions.CSharpNext,
         }.RunAsync();
     }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/76981")]
+    public async Task TestConvertWithReferencesToParameter1()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                namespace N
+                {
+                    internal class [|Goo(int bar)|]
+                    {
+                        public int Bar { get; private set; } = bar;
+
+                        public void Baz()
+                        {
+                            Bar = bar;
+                        }
+                    }
+                }
+                """,
+            FixedCode = """
+                namespace N
+                {
+                    internal class Goo
+                    {
+                        private readonly int bar;
+
+                        public Goo(int bar)
+                        {
+                            this.bar = bar;
+                            Bar = bar;
+                        }
+
+                        public int Bar { get; private set; }
+
+                        public void Baz()
+                        {
+                            Bar = bar;
+                        }
+                    }
+                }
+                """,
+            LanguageVersion = LanguageVersionExtensions.CSharpNext,
+        }.RunAsync();
+    }
 }