gccrs: fix ICE with bad match arm type

gccrs: fix ICE with bad match arm type

We expect to get some kind of ADT or Tuple type when computing this kind of
match arms this adds a new diagnostic to check for this case instead of
an assertion.

Fixes #2029

gcc/rust/ChangeLog:

	* typecheck/rust-hir-type-check-expr.cc (TypeCheckExpr::visit): return early on bad type
	* typecheck/rust-hir-type-check-pattern.cc (TypeCheckPattern::TypeCheckPattern):
	remove assertion in favor of check
	(TypeCheckPattern::visit): likewise

gcc/testsuite/ChangeLog:

	* rust/compile/issue-2029.rs: New test.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>