Desugar function calls without args

src/desugar.rs

@@ -1,4 +1,5 @@
 mod basic;
+mod call;
 mod expr;
 mod lit;
 mod program;

src/desugar/call.rs

@@ -0,0 +1,67 @@
+use crate::ast::{Call, Expr, Lit, Space};
+use crate::span::HasSpan;
+
+impl Call {
+    pub fn desugar(self) -> (Expr, bool) {
+        match self {
+            Self::Arg {
+                expr,
+                s0,
+                s1,
+                arg,
+                s2,
+                span,
+            } => {
+                let new = Expr::Call(Self::Arg {
+                    expr,
+                    s0,
+                    s1,
+                    arg,
+                    s2,
+                    span,
+                });
+                (new, false) // TODO Implement
+            }
+
+            Self::NoArg { expr, s0, s1, span } => {
+                let (expr, desugared) = expr.desugar();
+                if desugared {
+                    let new = Expr::Call(Self::NoArg {
+                        expr: Box::new(expr),
+                        s0,
+                        s1,
+                        span,
+                    });
+                    return (new, true);
+                }
+
+                let arg_span = s1.span().at_start();
+                let arg = Expr::Lit(Lit::Nil(arg_span));
+                let new = Expr::Call(Self::Arg {
+                    expr: Box::new(expr),
+                    s0,
+                    s1,
+                    arg: Box::new(arg),
+                    s2: Space::empty(arg_span.at_end()),
+                    span,
+                });
+                (new, true)
+            }
+
+            Self::Constr {
+                expr,
+                s0,
+                constr,
+                span,
+            } => {
+                let new = Expr::Call(Self::Constr {
+                    expr,
+                    s0,
+                    constr,
+                    span,
+                });
+                (new, false) // TODO Implement
+            }
+        }
+    }
+}

src/desugar/expr.rs

@@ -8,7 +8,8 @@ impl Expr {
                 (Self::Lit(lit), desugared)
             }
 
-            Self::Call(call) => (Self::Call(call), false), // TODO Implement
+            Self::Call(call) => call.desugar(),
+
             Self::Field(field) => (Self::Field(field), false), // TODO Implement
             Self::Var(var) => (Self::Var(var), false),         // TODO Implement
             Self::TableConstr(constr) => (Self::TableConstr(constr), false), // TODO Implement