// zeroConst returns a new "zero" constant of the specified type,
// which must not be an array or struct type: the zero values of
// aggregates are well-defined but cannot be represented by Const.
//
func zeroConst(t types.Type) *Const {
switch t := t.(type) {
case *types.Basic:
switch {
case t.Info()&types.IsBoolean != 0:
return NewConst(exact.MakeBool(false), t)
case t.Info()&types.IsNumeric != 0:
return NewConst(exact.MakeInt64(0), t)
case t.Info()&types.IsString != 0:
return NewConst(exact.MakeString(""), t)
case t.Kind() == types.UnsafePointer:
fallthrough
case t.Kind() == types.UntypedNil:
return nilConst(t)
default:
panic(fmt.Sprint("zeroConst for unexpected type:", t))
}
case *types.Pointer, *types.Slice, *types.Interface, *types.Chan, *types.Map, *types.Signature:
return nilConst(t)
case *types.Named:
return NewConst(zeroConst(t.Underlying()).Value, t)
case *types.Array, *types.Struct, *types.Tuple:
panic(fmt.Sprint("zeroConst applied to aggregate:", t))
}
panic(fmt.Sprint("zeroConst: unexpected ", t))
}
// Conversion type-checks the conversion T(x).
// The result is in x.
func (check *Checker) conversion(x *operand, T Type) {
constArg := x.mode == constant
var ok bool
switch {
case constArg && isConstType(T):
// constant conversion
switch t := T.Underlying().(*Basic); {
case representableConst(x.val, check.conf, t.kind, &x.val):
ok = true
case x.isInteger() && isString(t):
codepoint := int64(-1)
if i, ok := exact.Int64Val(x.val); ok {
codepoint = i
}
// If codepoint < 0 the absolute value is too large (or unknown) for
// conversion. This is the same as converting any other out-of-range
// value - let string(codepoint) do the work.
x.val = exact.MakeString(string(codepoint))
ok = true
}
case x.convertibleTo(check.conf, T):
// non-constant conversion
x.mode = value
ok = true
}
if !ok {
check.errorf(x.pos(), "cannot convert %s to %s", x, T)
x.mode = invalid
return
}
// The conversion argument types are final. For untyped values the
// conversion provides the type, per the spec: "A constant may be
// given a type explicitly by a constant declaration or conversion,...".
final := x.typ
if isUntyped(x.typ) {
final = T
// - For conversions to interfaces, use the argument's default type.
// - For conversions of untyped constants to non-constant types, also
// use the default type (e.g., []byte("foo") should report string
// not []byte as type for the constant "foo").
// - Keep untyped nil for untyped nil arguments.
if IsInterface(T) || constArg && !isConstType(T) {
final = defaultType(x.typ)
}
check.updateExprType(x.expr, final, true)
}
x.typ = T
}
// stringConst returns a 'string' constant that evaluates to s.
func stringConst(s string) *Const {
return NewConst(exact.MakeString(s), tString)
}
// CreateTestMainPackage creates and returns a synthetic "main"
// package that runs all the tests of the supplied packages, similar
// to the one that would be created by the 'go test' tool.
//
// It returns nil if the program contains no tests.
//
func (prog *Program) CreateTestMainPackage(pkgs ...*Package) *Package {
pkgs, tests, benchmarks, examples := FindTests(pkgs)
if len(pkgs) == 0 {
return nil
}
testmain := &Package{
Prog: prog,
Members: make(map[string]Member),
values: make(map[types.Object]Value),
Object: types.NewPackage("test$main", "main"),
}
// Build package's init function.
init := &Function{
name: "init",
Signature: new(types.Signature),
Synthetic: "package initializer",
Pkg: testmain,
Prog: prog,
}
init.startBody()
if testMainStartBodyHook != nil {
testMainStartBodyHook(init)
}
// Initialize packages to test.
var pkgpaths []string
for _, pkg := range pkgs {
var v Call
v.Call.Value = pkg.init
v.setType(types.NewTuple())
init.emit(&v)
pkgpaths = append(pkgpaths, pkg.Object.Path())
}
sort.Strings(pkgpaths)
init.emit(new(Return))
init.finishBody()
testmain.init = init
testmain.Object.MarkComplete()
testmain.Members[init.name] = init
// For debugging convenience, define an unexported const
// that enumerates the packages.
packagesConst := types.NewConst(token.NoPos, testmain.Object, "packages", tString,
exact.MakeString(strings.Join(pkgpaths, " ")))
memberFromObject(testmain, packagesConst, nil)
// Create main *types.Func and *ssa.Function
mainFunc := types.NewFunc(token.NoPos, testmain.Object, "main", new(types.Signature))
memberFromObject(testmain, mainFunc, nil)
main := testmain.Func("main")
main.Synthetic = "test main function"
main.startBody()
if testMainStartBodyHook != nil {
testMainStartBodyHook(main)
}
if testingPkg := prog.ImportedPackage("testing"); testingPkg != nil {
testingMain := testingPkg.Func("Main")
testingMainParams := testingMain.Signature.Params()
// The generated code is as if compiled from this:
//
// func main() {
// match := func(_, _ string) (bool, error) { return true, nil }
// tests := []testing.InternalTest{{"TestFoo", TestFoo}, ...}
// benchmarks := []testing.InternalBenchmark{...}
// examples := []testing.InternalExample{...}
// testing.Main(match, tests, benchmarks, examples)
// }
matcher := &Function{
name: "matcher",
Signature: testingMainParams.At(0).Type().(*types.Signature),
Synthetic: "test matcher predicate",
parent: main,
Pkg: testmain,
Prog: prog,
}
main.AnonFuncs = append(main.AnonFuncs, matcher)
matcher.startBody()
matcher.emit(&Return{Results: []Value{vTrue, nilConst(types.Universe.Lookup("error").Type())}})
matcher.finishBody()
// Emit call: testing.Main(matcher, tests, benchmarks, examples).
var c Call
c.Call.Value = testingMain
c.Call.Args = []Value{
matcher,
testMainSlice(main, tests, testingMainParams.At(1).Type()),
testMainSlice(main, benchmarks, testingMainParams.At(2).Type()),
testMainSlice(main, examples, testingMainParams.At(3).Type()),
}
emitTailCall(main, &c)
} else {
// The program does not import "testing", but FindTests
// returned non-nil, which must mean there were Examples
// but no Tests or Benchmarks.
// We'll simply call them from testmain.main; this will
// ensure they don't panic, but will not check any
// "Output:" comments.
for _, eg := range examples {
var c Call
c.Call.Value = eg
c.setType(types.NewTuple())
main.emit(&c)
}
main.emit(&Return{})
main.currentBlock = nil
}
main.finishBody()
testmain.Members["main"] = main
if prog.mode&PrintPackages != 0 {
printMu.Lock()
testmain.WriteTo(os.Stdout)
printMu.Unlock()
}
if prog.mode&SanityCheckFunctions != 0 {
sanityCheckPackage(testmain)
}
prog.packages[testmain.Object] = testmain
return testmain
}