_Range       // range
	_Return      // return
	_Select      // select
	_Struct      // struct
	_Switch      // switch
	_Type        // type
	_Var         // var

	// empty line comment to exclude it from .String
	tokenCount //
)

const (
	// for BranchStmt
	Break       = _Break
	Continue    = _Continue
	Fallthrough = _Fallthrough
	Goto        = _Goto

	// for CallStmt
	Go    = _Go

	// #8: specifying a permitted list of names does not exclude other name
	// types
	{
		roots: []constraintsSpec{
			{
				ok: []string{"dns:.example.com"},
			},
		},
		intermediates: [][]constraintsSpec{
			{
				{},
			},
		},
		leaf: leafSpec{
			sans: []string{"ip:10.1.1.1"},
		},
	},

	// #9: specifying a permitted list of names does not exclude other name
	// types
	{

)

type stdFilter int8

const (
	omitStd = stdFilter(iota)
	includeStd
)

// matchPackages is like m.MatchPackages, but uses a local variable (rather than
// a global) for tags, can include or exclude packages in the standard library,
// and is restricted to the given list of modules.
func matchPackages(ctx context.Context, m *search.Match, tags map[string]bool, filter stdFilter, modules []module.Version) {

of the modules.

By default, why queries the graph of packages matched by "go list all",
which includes tests for reachable packages. The -vendor flag causes why
to exclude tests of dependencies.

The output is a sequence of stanzas, one for each package or module
name on the command line, separated by blank lines. Each stanza begins
with a comment line "# package" or "# module" giving the target

	f, err := os.Open(filename)
	if err != nil {
		t.Error(err)
		return
	}

	// read file
	b1.Reset()
	_, err = io.Copy(b1, f)
	f.Close()
	if err != nil {
		t.Error(err)
		return
	}

	// exclude files w/ syntax errors (typically test cases)
	fset := token.NewFileSet()
	if _, _, _, err = parse(fset, filename, b1.Bytes(), false); err != nil {
		if *verbose {
			fmt.Fprintf(os.Stderr, "ignoring %s\n", err)
		}

	"-arch",
	"-D",
	"-U",
	"-I",
	"-F",
	"-framework",
	"-include",
	"-isysroot",
	"-isystem",
	"--sysroot",
	"-target",
	"-x",
}

var invalidLinkerFlags = []*lazyregexp.Regexp{
	// On macOS this means the linker loads and executes the next argument.
	// Have to exclude separately because -lfoo is allowed in general.
	re(`-lto_library`),
}

}
-- m/overlay/cgo_hello_quote.go --
package main

// #include "cgo_header.h"
import "C"

func main() {
	C.say_hello()
}
-- m/overlay/cgo_hello_angle.go --
package main

// #include <cgo_header.h>
import "C"

func main() {
	C.say_hello()
}
-- m/overlay/cgo_head.h --
void say_hello();
-- m/overlay/hello.c --
#include <stdio.h>

		panic("no error")
	}

	// Cheap trick: Don't report errors with messages containing
	// "invalid operand" or "invalid type" as those tend to be
	// follow-on errors which don't add useful information. Only
	// exclude them if these strings are not at the beginning,
	// and only if we have at least one error already reported.
	check := err.check
	if check.firstErr != nil {
		// It is sufficient to look at the first sub-error only.

//
// When viewed from the outside it also has a transitive dependency
// on v2.0.0+incompatible, but in lazy mode that transitive dependency
// is pruned out.
module example.net/lazy

go 1.17

exclude example.com/retract/incompatible v2.0.0+incompatible

require (
	example.com/retract/incompatible v1.0.0
	example.net/requireincompatible v0.1.0
)
-- requireincompatible/go.mod --

//
// When viewed from the outside it also has a transitive dependency
// on v2.0.0+incompatible, but in lazy mode that transitive dependency
// is pruned out.
module example.net/lazy

go 1.17

exclude example.com/retract/incompatible v2.0.0+incompatible

require (
	example.com/retract/incompatible v1.0.0
	example.net/requireincompatible v0.1.0
)
-- lazy/lazy.go --
package lazy
-- lazy/lazy_test.go --