Make type checker smarter at inferring l-expressions

Previously the following would fail:

```
default Order dec

$include <prelude.sail>

register V : vector(1, dec, vector(32, dec, bit))

val zeros : forall 'n, 'n >= 0. unit -> vector('n, dec, bit)

function main() : unit -> unit = {
  V[0] = zeros()
}
```

Since the type-checker wouldn't see that zeros() must have type
`vector(32, dec, bit)` from the type of `V[0]`. It now tries both to
infer the expression, and use that to check the assignment, and if
that fails we infer the lexp to check the assignment. This pattern
occurs a lot in ASL, and we often had to patch zeros() to zeros(32) or
similar there.

1 files changed, 11 insertions, 0 deletions

diff --git a/test/typecheck/pass/lexp_vec.sail b/test/typecheck/pass/lexp_vec.sail
new file mode 100644
index 00000000..605c3855
--- /dev/null
+++ b/test/typecheck/pass/lexp_vec.sail
@@ -0,0 +1,11 @@
+default Order dec
+
+$include <prelude.sail>
+
+register V : vector(1, dec, vector(32, dec, bit))
+
+val zeros : forall 'n, 'n >= 0. unit -> vector('n, dec, bit)
+
+function main() : unit -> unit = {
+  V[0] = zeros()
+}