tamer: Lower sum expressions

This was a fairly simple addition, since rate blocks already lower into sum
expressions; these are just non-identified.

This does emphasize that the nir::parse `ele_parse!` abstraction I spent so
much time on ended up not being a perfect fit, as it now has some
boilerplate after it was stripped of much of its capabilities some time ago.

Don't worry, `nir::air` and `asg::graph::xmli` will get cleaned up.

DEV-13708

tamer/src/asg/graph/xmli.rs

@@ -127,10 +127,9 @@ impl<'a> ParseState for AsgTreeToXirf<'a> {
 
                     toks.push(yields(ident.name(), expr.span()));
 
-                    Transition(Self::Ready(Default::default()))
-                        .ok(stmt(expr, depth))
+                    Transition(self).ok(stmt(expr, depth))
                 }
-                _ => todo!("non-ident expr"),
+                _ => Transition(self).ok(expr_ele(expr, depth)),
             },
 
             Object::Root(_) => diagnostic_unreachable!(
@@ -187,6 +186,15 @@ fn yields(name: SPair, span: Span) -> Xirf {
     Xirf::attr(QN_YIELDS, name, (span, name))
 }
 
+fn expr_ele(expr: &Expr, depth: Depth) -> Xirf {
+    let qname = match expr.op() {
+        ExprOp::Sum => QN_C_SUM,
+        op => todo!("expr_ele qname: {op:?}"),
+    };
+
+    Xirf::open(qname, OpenSpan::without_name_span(expr.span()), depth)
+}
+
 pub struct TreeContext<'a>(TokenStack, &'a Asg);
 
 // Custom `Debug` impl to omit ASG rendering,

tamer/src/nir.rs

@@ -184,6 +184,9 @@ pub enum NirEntity {
     ///   representing a calculation with a scalar result.
     Rate,
 
+    /// Summation (Σ) expression.
+    Sum,
+
     /// Template parameter (metavariable).
     TplParam,
 }
@@ -205,6 +208,7 @@ impl Display for NirEntity {
         match self {
             Package => write!(f, "package"),
             Rate => write!(f, "rate block"),
+            Sum => write!(f, "sum expression"),
             TplParam => write!(f, "template param (metavariable)"),
         }
     }

tamer/src/nir/air.rs

@@ -74,11 +74,11 @@ impl ParseState for NirToAir {
                 Transition(Ready).ok(Air::PkgClose(span))
             }
 
-            (Ready, Nir::Open(NirEntity::Rate, span)) => {
+            (Ready, Nir::Open(NirEntity::Rate | NirEntity::Sum, span)) => {
                 Transition(Ready).ok(Air::ExprOpen(ExprOp::Sum, span))
             }
 
-            (Ready, Nir::Close(NirEntity::Rate, span)) => {
+            (Ready, Nir::Close(NirEntity::Rate | NirEntity::Sum, span)) => {
                 Transition(Ready).ok(Air::ExprClose(span))
             }
 

tamer/src/nir/air/test.rs

@@ -56,3 +56,19 @@ fn rate_to_sum_expr() {
         Sut::parse(toks.into_iter()).collect(),
     );
 }
+
+#[test]
+fn calc_expr() {
+    let toks = vec![
+        Nir::Open(NirEntity::Sum, S1),
+        Nir::Close(NirEntity::Sum, S2),
+    ];
+
+    assert_eq!(
+        Ok(vec![
+            O(Air::ExprOpen(ExprOp::Sum, S1)),
+            O(Air::ExprClose(S2)),
+        ]),
+        Sut::parse(toks.into_iter()).collect(),
+    );
+}

tamer/src/nir/parse.rs

@@ -664,7 +664,7 @@ ele_parse! {
     ///   identified by [`@generates`](QN_GENERATES).
     ///
     /// Summation is generated automatically by [`RateEachStmt`].
-    SumExpr := QN_C_SUM {
+    SumExpr := QN_C_SUM(_, ospan) {
         @ {
             QN_OF => TodoAttr,
             QN_GENERATES => TodoAttr,
@@ -673,7 +673,8 @@ ele_parse! {
             QN_LABEL => TodoAttr,
             QN_SYM => TodoAttr,
             QN_DIM => TodoAttr,
-        } => Todo,
+        } => NirEntity::Sum.open(ospan),
+        /(cspan) => NirEntity::Sum.close(cspan),
 
         WhenExpr,
         CalcExpr,

tamer/tests/xmli/expected.xml

@@ -3,6 +3,19 @@
          xmlns:t="http://www.lovullo.com/rater/apply-template">
 
   <rate yields="rateFoo" />
-  <rate yields="rateBar" />
+
+  <rate yields="rateBar">
+    <c:sum />
+  </rate>
+
+  <rate yields="rateBaz">
+    <c:sum>
+      <c:sum />
+    </c:sum>
+    <c:sum>
+      <c:sum />
+      <c:sum />
+    </c:sum>
+  </rate>
 </package>
 

tamer/tests/xmli/src.xml

@@ -7,6 +7,19 @@
   The output `out.xmli` is asserted against `expected.xml`.
 
   <rate yields="rateFoo" />
-  <rate yields="rateBar" />
+
+  <rate yields="rateBar">
+    <c:sum />
+  </rate>
+
+  <rate yields="rateBaz">
+    <c:sum>
+      <c:sum />
+    </c:sum>
+    <c:sum>
+      <c:sum />
+      <c:sum />
+    </c:sum>
+  </rate>
 </package>