parser comments

1 files changed, 10 insertions, 0 deletions

diff --git a/src/libsyntax/parse/classify.rs b/src/libsyntax/parse/classify.rs
index 840fb891bff..e04914c0f1e 100644
--- a/src/libsyntax/parse/classify.rs
+++ b/src/libsyntax/parse/classify.rs
@@ -15,6 +15,13 @@
 use ast;
 use codemap;
 
+// does this expression require a semicolon to be treated
+// as a statement? The negation of this: 'can this expression
+// be used as a statement without a semicolon' -- is used
+// as an early-bail-out in the parser so that, for instance,
+// 'if true {...} else {...}
+//  |x| 5 '
+// isn't parsed as (if true {...} else {...} | x) | 5
 pub fn expr_requires_semi_to_be_stmt(e: @ast::expr) -> bool {
     match e.node {
       ast::expr_if(*)
@@ -40,6 +47,9 @@ pub fn expr_is_simple_block(e: @ast::expr) -> bool {
     }
 }
 
+// this statement requires a semicolon after it.
+// note that in one case (stmt_semi), we've already
+// seen the semicolon, and thus don't need another.
 pub fn stmt_ends_with_semi(stmt: &ast::stmt) -> bool {
     return match stmt.node {
         ast::stmt_decl(d, _) => {