[ASTGen] The 'extendedType' argument for attached macros does not have a

source location.

(cherry picked from commit 43e2026)

Author: hborla

lib/ASTGen/Sources/ASTGen/Macros.swift

@@ -819,7 +819,7 @@ func expandAttachedMacroIPC(
   let extendedTypeSyntax: PluginMessage.Syntax?
   if (!qualifiedType.isEmpty) {
     let typeSyntax: TypeSyntax = "\(raw: qualifiedType)"
-    extendedTypeSyntax = .init(syntax: Syntax(typeSyntax), in: parentDeclSourceFilePtr!)!
+    extendedTypeSyntax = .init(syntax: Syntax(typeSyntax))!
   } else {
     extendedTypeSyntax = nil
   }

lib/ASTGen/Sources/ASTGen/PluginHost.swift

@@ -397,4 +397,31 @@ extension PluginMessage.Syntax {
         line: loc.line,
         column: loc.column))
   }
+
+  init?(syntax: Syntax) {
+    let kind: PluginMessage.Syntax.Kind
+    switch true {
+    case syntax.is(DeclSyntax.self): kind = .declaration
+    case syntax.is(ExprSyntax.self): kind = .expression
+    case syntax.is(StmtSyntax.self): kind = .statement
+    case syntax.is(TypeSyntax.self): kind = .type
+    case syntax.is(PatternSyntax.self): kind = .pattern
+    case syntax.is(AttributeSyntax.self): kind = .attribute
+    default: return nil
+    }
+
+    let source = syntax.description
+
+    self.init(
+      kind: kind,
+      source: source,
+      location: .init(
+        fileID: "",
+        fileName: "",
+        offset: 0,
+        line: 0,
+        column: 0
+      )
+    )
+  }
 }