From 8a0ebb2b607c92b8c1bdab7e525da2b711b31565 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Mon, 15 Jan 2024 08:49:57 +0200
Subject: Automatically alias unknown target types of imported targets

---
 libbuild2/file.hxx | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

(limited to 'libbuild2/file.hxx')

diff --git a/libbuild2/file.hxx b/libbuild2/file.hxx
index 68c284b..36e4c00 100644
--- a/libbuild2/file.hxx
+++ b/libbuild2/file.hxx
@@ -371,7 +371,18 @@ namespace build2
   //
   enum class import_kind {adhoc, normal, fallback};
 
-  LIBBUILD2_SYMEXPORT pair<names, import_kind>
+  template <typename T>
+  struct import_result
+  {
+    const T*    target; // Note: T can be imported target or imported scope.
+    names       name;
+    import_kind kind;
+  };
+
+  // Note that import_result<scope>::target may be NULL even if name is not
+  // empty (e.g, out of project target imported via phase 2).
+  //
+  LIBBUILD2_SYMEXPORT import_result<scope>
   import (scope& base,
           name,
           const optional<string>& phase2,
@@ -409,14 +420,6 @@ namespace build2
   //
   // Note: cannot be used to import buildfile targets (use import_buildfile()
   // instead).
-  //
-  template <typename T>
-  struct import_result
-  {
-    const T*    target;
-    names       name;
-    import_kind kind;
-  };
 
   // Print import_direct<exe>() result either as a target for a normal import
   // or as a process path for ad hoc and fallback imports. Normally used in
@@ -518,6 +521,16 @@ namespace build2
                bool metadata,
                const location&);
 
+  // Import (more precisely, alias as if using the `define =` syntax) the
+  // target type from imported project (iroot) into this project (root). If
+  // the target type with this name is already defined in this project, then
+  // make sure it is the same as in the imported project.
+  //
+  LIBBUILD2_SYMEXPORT const target_type&
+  import_target_type (scope& root,
+                      const scope& iroot, const string&,
+                      const location&);
+
   // Suggest appropriate ways to import the specified target (as type and
   // name) from the specified project.
   //
-- 
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