resolve return type of @extern

@Rexicon226 You're welcome

Author: Techatrix

src/analysis.zig

@@ -1793,6 +1793,7 @@ fn resolveTypeOfNodeUncached(analyser: *Analyser, node_handle: NodeWithHandle) e
                 .{"@atomicLoad"},
                 .{"@atomicRmw"},
                 .{"@atomicStore"},
+                .{"@extern"},
                 .{"@mulAdd"},
                 .{"@unionInit"},
             });

tests/lsp_features/completion.zig

@@ -2495,6 +2495,21 @@ test "@FieldType" {
     });
 }
 
+test "@extern" {
+    try testCompletion(
+        \\test {
+        \\    const S = struct {
+        \\        alpha: u32,
+        \\    };
+        \\    const foo = @extern(*S, .{});
+        \\    foo.<cursor>
+        \\}
+    , &.{
+        .{ .label = "*", .kind = .Operator, .detail = "S" },
+        .{ .label = "alpha", .kind = .Field, .detail = "u32" },
+    });
+}
+
 test "builtin fns return type" {
     try testCompletion(
         \\pub const chip_mod = struct {