xo-expression: add explicit types to all Expressions

src/expression/IfExpr.cpp

@@ -4,7 +4,34 @@
 #include "xo/indentlog/print/vector.hpp"
 
 namespace xo {
+    using xo::ref::rp;
+
     namespace ast {
+        rp<IfExpr>
+        IfExpr::make(const rp<Expression> & test,
+                     const rp<Expression> & when_true,
+                     const rp<Expression> & when_false)
+        {
+            /** TODO: verify test returns _boolean_ type **/
+
+            if (when_true->valuetype() != when_false->valuetype()) {
+                throw std::runtime_error
+                    (tostr("IfExpr::make:"
+                           " types {T1,T2} found for branches of if-expr"
+                           " where equal types expected",
+                           xtag("T1", when_true->valuetype()->canonical_name()),
+                           xtag("T2", when_false->valuetype()->canonical_name())));
+            }
+
+            /* arbitrary choice here */
+            auto ifexpr_type = when_true->valuetype();
+
+            return new IfExpr(ifexpr_type,
+                              test,
+                              when_true,
+                              when_false);
+        } /*make*/
+
         void
         IfExpr::display(std::ostream & os) const {
             os << "<IfExpr"