go/types: better cycle reporting for some cyclic composite literals
To evaluate the type of composite literals, the type checker called
Checker.typ which breaks cycles. As a result, certain cycles were
not reported with actual cycle reporting, but caught due to other
uninitialized fields (with less nice error message).
The change now calls Checker.typExpr at the relevant call site.
For #18643.
Change-Id: Iecb3f0e1afb4585b85553b6c581212f52ac3a1c4
Reviewed-on: https://go-review.googlesource.com/115456 Reviewed-by: Alan Donovan <adonovan@google.com>