Go patch committed: Don't crash on cyclic var/type dependencies

[Ian Lance Taylor <iant at golang dot org>]

This patch by Than McIntosh fixes type traversal in the Go frontend to
avoid compiler crashes for test cases where a type T includes an
expression that refers back to the type without actually explicitly
mentioning T. Examples include:

  var x [uintptr(unsafe.Sizeof(&x))]byte
  var a [len(a)]int

The fix involves expanding the set of types that the traversal code
"remembers" (to avoid cycles) to include array types, and introducing
an additional guard in Builtin_call_expression::do_is_constant to
catch cyclic type constructs.

Fixes https://golang.org/issue/{25299,25679,25315,25680}.

Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu.  Committed
to mainline.

Ian

Attachment: patch.txt
Description: Text document