manual: link to expressions in lval/rval section.

Author: graydon

doc/rust.md

@@ -1476,11 +1476,15 @@ Expressions are divided into two main categories: _lvalues_ and _rvalues_.
 Likewise within each expression, sub-expressions may occur in _lvalue context_ or _rvalue context_.
 The evaluation of an expression depends both on its own category and the context it occurs within.
 
-Path, field and index expressions are lvalues.
+[Path](#path-expressions), [field](#field-expressions) and [index](#index-expressions) expressions are lvalues.
 All other expressions are rvalues.
 
-The left operand of an assignment, compound-assignment, or binary move expression is an lvalue context,
-as is the single operand of a borrow, unary copy or move expression, and _both_ operands of a swap expression.
+The left operand of an [assignment](#assignment-expressions) or
+[compound-assignment](#compound-assignment-expressions) expression is an lvalue context,
+as is the single operand of a unary [borrow](#unary-operator-expressions),
+or [move](#unary-move-expressions) expression,
+and _both_ operands of a [swap](#swap-expressions)
+or [binary move](#binary-move-expressions) expression.
 All other expression contexts are rvalue contexts.
 
 When an lvalue is evaluated in an _lvalue context_, it denotes a memory location;