xo-expression: add explicit types to all Expressions

src/expression/Apply.cpp

@@ -4,7 +4,29 @@
 #include "xo/indentlog/print/vector.hpp"
 
 namespace xo {
+    using xo::ref::rp;
+
     namespace ast {
+        rp<Apply>
+        Apply::make(const rp<Expression> & fn,
+                    const std::vector<rp<Expression>> & argv)
+        {
+            /* extract result type from function type */
+            TypeDescr fn_valuetype = fn->valuetype();
+
+            if (!fn_valuetype->is_function()) {
+                throw std::runtime_error
+                    (tostr("Apply::make: found expression F in function position,"
+                           " with value-type FT where a function type expected",
+                           xtag("FT", fn_valuetype->short_name()),
+                           xtag("F", fn_valuetype)));
+            }
+
+            TypeDescr fn_retval_type = fn_valuetype->fn_retval();
+
+            return new Apply(fn_retval_type, fn, argv);
+        }
+
         void
         Apply::display(std::ostream & os) const {
             os << "<Apply"