Create new objects with existing span

I've decided that attempting to create smaller spans is more difficult
and will also lead to worse error messages later on. It makes more sense
to just tag every newly created syntax tree element with the span of the
element it comes from.

src/desugar/call.rs

@@ -1,5 +1,4 @@
 use crate::ast::{Call, Expr, Ident, Lit, Separated, Space, TableLit, TableLitElem};
-use crate::span::HasSpan;
 
 // TODO Add span for just the parentheses to ast, or limit span to parentheses
 
@@ -81,14 +80,13 @@ impl Call {
                     return (new, true);
                 }
 
-                let arg_span = s1.span().at_start();
+                let arg = Expr::Lit(Lit::Nil(span));
-                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()),
+                    s2: Space::empty(span),
                     span,
                 });
                 (new, true)
@@ -112,13 +110,12 @@ impl Call {
                 }
 
                 let arg = Expr::TableConstr(constr);
-                let arg_span = arg.span();
                 let new = Expr::Call(Self::Arg {
                     expr: Box::new(expr),
                     s0,
-                    s1: Space::empty(arg_span.at_start()),
+                    s1: Space::empty(span),
                     arg: Box::new(arg),
-                    s2: Space::empty(arg_span.at_end()),
+                    s2: Space::empty(span),
                     span,
                 });
                 (new, true)

src/desugar/program.rs

@@ -1,5 +1,4 @@
 use crate::ast::{Expr, Lit, Program, Space, TableLit};
-use crate::span::HasSpan;
 
 impl Program {
     pub fn desugar(self) -> (Self, bool) {
@@ -25,14 +24,14 @@ impl Program {
                         s2,
                         span,
                     };
-                    (new, true)
+                    return (new, true);
-                } else {
+                }
-                    let elems_span = elems.span();
+
                 let table = TableLit {
                     s0: s1,
                     elems,
-                        s1: Space::empty(elems_span.at_end()),
+                    s1: Space::empty(span),
-                        span: elems_span,
+                    span,
                 };
                 let new = Self::Expr {
                     s0,
@@ -45,4 +44,3 @@ impl Program {
         }
     }
 }
-}

src/span.rs

@@ -24,14 +24,6 @@ impl Span {
         let end = self.end.max(other.end);
         Self::new(start, end)
     }
-
-    pub fn at_start(self) -> Self {
-        Self::new(self.start, self.start)
-    }
-
-    pub fn at_end(self) -> Self {
-        Self::new(self.end, self.end)
-    }
 }
 
 impl fmt::Debug for Span {