lang: Improve graph shape with speculative execution

Most of the time, we don't need to have a dynamic call sub graph, since
the actual function call could be represented statically as it
originally was before lambda functions were implemented. Simplifying the
graph shape has important performance benefits in terms of both keep the
graph smaller (memory, etc) and in avoiding the need to run transactions
at runtime (speed) to reshape the graph.

Co-authored-by: Samuel Gélineau <gelisam@gmail.com>

lang/core/map/map_lookup.go

@@ -204,6 +204,13 @@ func (obj *MapLookupFunc) Build(typ *types.Type) (*types.Type, error) {
 
 	obj.Func = &wrapped.Func{
 		Name: obj.String(),
+		FuncInfo: &wrapped.Info{
+			// TODO: dedup with below Info data
+			Pure: true,
+			Memo: true,
+			Fast: true,
+			Spec: true,
+		},
 		Type: typ, // .Copy(),
 	}
 
@@ -232,6 +239,9 @@ func (obj *MapLookupFunc) Copy() interfaces.Func {
 // Call is the actual implementation here. This is used in lieu of the Stream
 // function which we'd have these contents within.
 func (obj *MapLookupFunc) Call(ctx context.Context, args []types.Value) (types.Value, error) {
+	if len(args) < 2 {
+		return nil, fmt.Errorf("not enough args")
+	}
 	m := (args[0]).(*types.MapValue)
 	key := args[1]
 	//zero := m.Type().Val.New() // the zero value
@@ -266,7 +276,9 @@ func (obj *MapLookupFunc) Validate() error {
 func (obj *MapLookupFunc) Info() *interfaces.Info {
 	return &interfaces.Info{
 		Pure: true,
-		Memo: false,
+		Memo: true,
+		Fast: true,
+		Spec: true,
 		Sig:  obj.sig(), // helper
 		Err:  obj.Validate(),
 	}