Small IR docs, and then some learning about rustdoc.

src/ir/from_syntax.rs

@@ -1,7 +1,7 @@
 use internment::ArcIntern;
 
 use crate::ir::ast as ir;
-use crate::syntax::ast as syntax;
+use crate::syntax as syntax;
 
 impl From<syntax::Program> for ir::Program {
     fn from(mut value: syntax::Program) -> Self {