The nodecount program illustrates the use of packages.Load to print the frequency of occurrence of each type of syntax node among the selected packages.
Example usage:
$ nodecount golang.org/x/tools/... std
A typical distribution is 40% identifiers, 10% literals, 8% selectors, and 6% calls; around 3% each of BinaryExpr, BlockStmt, AssignStmt, Field, and Comment; and the rest accounting for 20%.