fix link resolution regression caused by duplicate feature edges

Author: tayloraswift

Sources/SymbolGraphCompiler/Extensions/SSGC.Extensions.swift

@@ -24,6 +24,13 @@ extension SSGC
     }
 }
 extension SSGC.Extensions
+{
+    var all:Dictionary<SSGC.ExtensionSignature, SSGC.ExtensionObject>.Values
+    {
+        self.groups.values
+    }
+}
+extension SSGC.Extensions
 {
     mutating
     func include(_ vertex:SymbolGraphPart.Vertex,
@@ -114,7 +121,7 @@ extension SSGC.Extensions
         /// Gather extension members attributable to the specified culture, simplifying the
         /// extension signatures by inspecting the extended declaration. This may coalesce
         /// multiple extension objects into a single extension layer.
-        let coalesced:[SSGC.Extension.ID: SSGC.ExtensionLayer] = try self.groups.values.reduce(
+        let coalesced:[SSGC.Extension.ID: SSGC.ExtensionLayer] = try self.all.reduce(
             into: [:])
         {
             let blocks:[(id:Symbol.Block, block:SSGC.Extension.Block)] = $1.blocks.reduce(

Sources/SymbolGraphCompiler/SSGC.TypeChecker.swift

@@ -525,16 +525,29 @@ extension SSGC.TypeChecker
                     """)
             }
         }
-
-        self.resolvableLinks[heir.namespace, heir.value.path, feature.value.path.last].append(
-            .feature(feature.value, self: heir.id))
     }
 }
 extension SSGC.TypeChecker
 {
-    public __consuming
+    public consuming
     func load(in culture:Symbol.Module) throws -> SSGC.ModuleIndex
     {
+        for `extension`:SSGC.ExtensionObject in self.extensions.all
+        {
+            //  We add the feature paths here and not in `insert(_:by:)` because those
+            //  edges are frequently duplicated, and it is hard to remove duplicate paths
+            //  after they have been added.
+            let extendee:SSGC.DeclObject = try self.declarations[`extension`.extendee]
+            for feature:Symbol.Decl in `extension`.features.keys
+            {
+                let feature:SSGC.Decl = try self.declarations[feature].value
+                let last:String = feature.path.last
+
+                self.resolvableLinks[extendee.namespace, extendee.value.path, last].append(
+                    .feature(feature, self: extendee.id))
+            }
+        }
+
         let extensions:[SSGC.Extension] = try self.extensions.load(culture: culture,
             with: self.declarations)