parse: More godoc.

parse/node.go

@@ -24,6 +24,8 @@ func (n *node) n() *node {
 	return n
 }
 
+// Parent returns the parent node. If the node is the root of the syntax tree,
+// the parent is nil.
 func (n *node) Parent() Node {
 	return n.parent
 }
@@ -37,15 +39,17 @@ func (n *node) End() int {
 }
 
 // Range returns the range within the original (full) source text that parses
-// into the node.
+// to the node.
 func (n *node) Range() diag.Ranging {
 	return diag.Ranging{n.begin, n.end}
 }
 
+// SourceText returns the part of the source text that parses to the node.
 func (n *node) SourceText() string {
 	return n.sourceText
 }
 
+// Children returns all children of the node in the parse tree.
 func (n *node) Children() []Node {
 	return n.children
 }

parse/parse.go

@@ -1,4 +1,10 @@
 // Package parse implements the elvish parser.
+//
+// The parser builds a hybrid of AST (abstract syntax tree) and parse tree
+// (a.k.a. concrete syntax tree). The AST part only includes parts that are
+// semantically important, and is embodied in the fields of each *Node type. The
+// parse tree part corresponds to all the text in the original source text, and
+// is embodied in the children of each *Node type.
 package parse
 
 //go:generate ./boilerplate.py