Implement multi-valued functions, multi-valued return, and

unpacking for assignments, call arguments, and returns.  This
change revamps the whole assignment compilation system to be
multi-valued, using the new MultiType type and multiV value.
Function calls, returns, and assignments now share a lot of
code and produce very consistent error messages.

R=rsc
APPROVED=rsc
DELTA=510  (335 added, 74 deleted, 101 changed)
OCL=32248
CL=32258

1 files changed, 32 insertions, 0 deletions

diff --git a/usr/austin/eval/value.go b/usr/austin/eval/value.go
index b050448a7..de5813e6d 100644
--- a/usr/austin/eval/value.go
+++ b/usr/austin/eval/value.go
@@ -537,6 +537,38 @@ func (t *FuncType) Zero() Value {
 }
 
 /*
+ * Multi-values
+ */
+
+type multiV []Value
+
+func (v multiV) String() string {
+	res := "(";
+	for i, v := range v {
+		if i > 0 {
+			res += ", ";
+		}
+		res += v.String();
+	}
+	return res + ")";
+}
+
+func (v multiV) Assign(o Value) {
+	omv := o.(multiV);
+	for i := range v {
+		v[i].Assign(omv[i]);
+	}
+}
+
+func (t *MultiType) Zero() Value {
+	res := make([]Value, len(t.Elems));
+	for i := 0; i < len(t.Elems); i++ {
+		res[i] = t.Elems[i].Zero();
+	}
+	return multiV(res);
+}
+
+/*
  * Universal constants
  */