Support 'view call hierarchy' on primary consstructor

src/Features/Core/Portable/FindUsages/FindUsagesHelpers.cs

@@ -8,6 +8,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.FindSymbols;
+using Microsoft.CodeAnalysis.LanguageService;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.SymbolMapping;
 
@@ -18,25 +19,40 @@ internal static class FindUsagesHelpers
     public static string GetDisplayName(ISymbol symbol)
         => symbol.IsConstructor() ? symbol.ContainingType.Name : symbol.Name;
 
+    public static Task<(ISymbol symbol, Project project)?> GetRelevantSymbolAndProjectAtPositionAsync(
+        Document document, int position, CancellationToken cancellationToken)
+        => GetRelevantSymbolAndProjectAtPositionAsync(document, position, preferPrimaryConstructor: false, cancellationToken);
+
     /// <summary>
-    /// Common helper for both the synchronous and streaming versions of FAR. 
-    /// It returns the symbol we want to search for and the solution we should
-    /// be searching.
-    /// 
-    /// Note that the <see cref="Solution"/> returned may absolutely *not* be
-    /// the same as <c>document.Project.Solution</c>.  This is because 
-    /// there may be symbol mapping involved (for example in Metadata-As-Source
-    /// scenarios).
+    /// Common helper for both the synchronous and streaming versions of FAR. It returns the symbol we want to search
+    /// for and the solution we should be searching.
+    /// <para/> Note that the <see cref="Solution"/> returned may absolutely *not* be the same as
+    /// <c>document.Project.Solution</c>.  This is because there may be symbol mapping involved (for example in
+    /// Metadata-As-Source scenarios).
     /// </summary>
+    /// <param name="preferPrimaryConstructor">Whether the named type or primary constructor should be preferred if the
+    /// position is on a type-header fof a type declaration that has primary constructor parameters.</param>
     public static async Task<(ISymbol symbol, Project project)?> GetRelevantSymbolAndProjectAtPositionAsync(
-        Document document, int position, CancellationToken cancellationToken)
+        Document document, int position, bool preferPrimaryConstructor, CancellationToken cancellationToken)
     {
         cancellationToken.ThrowIfCancellationRequested();
 
-        var symbol = await SymbolFinder.FindSymbolAtPositionAsync(document, position, cancellationToken: cancellationToken).ConfigureAwait(false);
+        var symbol = await SymbolFinder.FindSymbolAtPositionAsync(document, position, cancellationToken).ConfigureAwait(false);
         if (symbol == null)
             return null;
 
+        if (preferPrimaryConstructor && symbol is INamedTypeSymbol namedType)
+        {
+            var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
+            var headerFacts = document.GetRequiredLanguageService<IHeaderFactsService>();
+            var semanticFacts = document.GetRequiredLanguageService<ISemanticFactsService>();
+            if (headerFacts.IsOnTypeHeader(root, position, out _) &&
+                semanticFacts.TryGetPrimaryConstructor(namedType, out var primaryConstructor))
+            {
+                symbol = primaryConstructor;
+            }
+        }
+
         // If this document is not in the primary workspace, we may want to search for results
         // in a solution different from the one we started in. Use the starting workspace's
         // ISymbolMappingService to get a context for searching in the proper solution.