Fix requirement candidate lookup to prefer decls in the same paraent as the inheritance decl. (#5965)

3 files changed, 32 insertions, 1 deletions

diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index c9497ce54..3fea267ee 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -6541,7 +6541,25 @@ bool SemanticsVisitor::findWitnessForInterfaceRequirement(
             }
         }
     }
-
+    if (lookupResult.isOverloaded())
+    {
+        // If we found multiple members with the same name,
+        // we want to move the declarations in the same parent as inheritanceDecl
+        // to the front of the list, so that we always consider them first instead of
+        // the members declared in other extension decls.
+        //
+        Index front = 0;
+        auto parentOfInheritanceDecl = getParentAggTypeDeclBase(inheritanceDecl);
+        for (Index i = 0; i < lookupResult.items.getCount(); i++)
+        {
+            if (getParentAggTypeDeclBase(lookupResult.items[i].declRef.getDecl()) ==
+                parentOfInheritanceDecl)
+            {
+                lookupResult.items.swapElements(i, front);
+                front++;
+            }
+        }
+    }
     // Iterate over the members and look for one that matches
     // the expected signature for the requirement.
     for (auto member : lookupResult)
diff --git a/source/slang/slang-syntax.cpp b/source/slang/slang-syntax.cpp
index 1d3763299..5dc6ca695 100644
--- a/source/slang/slang-syntax.cpp
+++ b/source/slang/slang-syntax.cpp
@@ -1051,6 +1051,18 @@ Decl* getParentAggTypeDecl(Decl* decl)
     return nullptr;
 }
 
+Decl* getParentAggTypeDeclBase(Decl* decl)
+{
+    decl = decl->parentDecl;
+    while (decl)
+    {
+        if (as<AggTypeDeclBase>(decl))
+            return decl;
+        decl = decl->parentDecl;
+    }
+    return nullptr;
+}
+
 Decl* getParentFunc(Decl* decl)
 {
     while (decl)
diff --git a/source/slang/slang-syntax.h b/source/slang/slang-syntax.h
index 5e31b5447..accc490f2 100644
--- a/source/slang/slang-syntax.h
+++ b/source/slang/slang-syntax.h
@@ -370,6 +370,7 @@ Module* getModule(Decl* decl);
 /// Get the parent decl, skipping any generic decls in between.
 Decl* getParentDecl(Decl* decl);
 Decl* getParentAggTypeDecl(Decl* decl);
+Decl* getParentAggTypeDeclBase(Decl* decl);
 Decl* getParentFunc(Decl* decl);
 
 } // namespace Slang