instantiation_expression syntax nodes were not included in the list of basic expressions, and thus the @expr.lexical_scope graph node was not being created for them. This caused an error in the stanza that deals with function arguments, e.g.:

0: Error executing statement edge @arg.lexical_scope -> @args.lexical_scope at (3515, 3)
     src/stack-graphs.tsg:3515:3:
     3515 |   edge @arg.lexical_scope -> @args.lexical_scope
          |   ^
     in stanza
     src/stack-graphs.tsg:3511:1:
     3511 | (arguments (_)@arg)@args {
          | ^
     matching (arguments) node
     test/test.ts:3:4:
     3 | foo(Bar<string>);
       |    ^
1: Evaluating edge source
2: Undefined scoped variable [syntax node instantiation_expression (3, 5)].lexical_scop

Simply including instantiation_expression syntax nodes in the list fixe the issue. Copious testing (on our TS test suite and on all of microsoft/vscode) reveals no negative side effects.

Actually resolving a reference appearing in an instantiation expression as call argument does not work — I left a TODO.