go/types: make tracing configurable (matching types2)

This CL replaces the internal trace flag with Config.trace.
While unexported, it can still be set for testing via reflection.
The typical use is for manual tests, where -v (verbose) turns on
tracing output. Typical use:

        go test -run Manual -v

This change makes go/types match types2 behavior.

Change-Id: I22842f4bba8fd632efe5929c950f4b1cab0a8569
Reviewed-on: https://go-review.googlesource.com/c/go/+/461081
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>

src/go/types/api.go

@@ -143,6 +143,9 @@ type Config struct {
 	// It is an error to set both FakeImportC and go115UsesCgo.
 	go115UsesCgo bool
 
+	// If trace is set, a debug trace is printed to stdout.
+	trace bool
+
 	// If Error != nil, it is called with each error found
 	// during type checking; err has dynamic type Error.
 	// Secondary errors (for instance, to enumerate all types

src/go/types/call.go

@@ -65,7 +65,7 @@ func (check *Checker) instantiateSignature(pos token.Pos, typ *Signature, targs
 	assert(check != nil)
 	assert(len(targs) == typ.TypeParams().Len())
 
-	if trace {
+	if check.conf.trace {
 		check.trace(pos, "-- instantiating signature %s with %s", typ, targs)
 		check.indent++
 		defer func() {

src/go/types/check.go

@@ -16,10 +16,7 @@ import (
 )
 
 // debugging/development support
-const (
-	debug = false // leave on during development
-	trace = false // turn on for detailed type resolution traces
-)
+const debug = false // leave on during development
 
 // exprInfo stores information about an untyped expression.
 type exprInfo struct {
@@ -313,7 +310,7 @@ func (check *Checker) checkFiles(files []*ast.File) (err error) {
 	defer check.handleBailout(&err)
 
 	print := func(msg string) {
-		if trace {
+		if check.conf.trace {
 			fmt.Println()
 			fmt.Println(msg)
 		}
@@ -377,7 +374,7 @@ func (check *Checker) processDelayed(top int) {
 	// this is a sufficiently bounded process.
 	for i := top; i < len(check.delayed); i++ {
 		a := &check.delayed[i]
-		if trace {
+		if check.conf.trace {
 			if a.desc != nil {
 				check.trace(a.desc.pos.Pos(), "-- "+a.desc.format, a.desc.args...)
 			} else {
@@ -385,7 +382,7 @@ func (check *Checker) processDelayed(top int) {
 			}
 		}
 		a.f() // may append to check.delayed
-		if trace {
+		if check.conf.trace {
 			fmt.Println()
 		}
 	}

src/go/types/check_test.go

@@ -145,7 +145,7 @@ func testFiles(t *testing.T, sizes Sizes, filenames []string, srcs [][]byte, man
 	flags := flag.NewFlagSet("", flag.PanicOnError)
 	flags.StringVar(&conf.GoVersion, "lang", "", "")
 	flags.BoolVar(&conf.FakeImportC, "fakeImportC", false, "")
-	flags.BoolVar(addrOldComparableSemantics(&conf), "oldComparableSemantics", false, "")
+	flags.BoolVar(boolFieldAddr(&conf, "oldComparableSemantics"), "oldComparableSemantics", false, "")
 	if err := parseFlags(filenames[0], srcs[0], flags); err != nil {
 		t.Fatal(err)
 	}
@@ -166,6 +166,7 @@ func testFiles(t *testing.T, sizes Sizes, filenames []string, srcs [][]byte, man
 	}
 
 	// typecheck and collect typechecker errors
+	*boolFieldAddr(&conf, "trace") = manual && testing.Verbose()
 	if imp == nil {
 		imp = importer.Default()
 	}
@@ -299,10 +300,11 @@ func readCode(err Error) int {
 	return int(v.FieldByName("go116code").Int())
 }
 
-// addrOldComparableSemantics(conf) returns &conf.oldComparableSemantics (unexported field).
-func addrOldComparableSemantics(conf *Config) *bool {
+// boolFieldAddr(conf, name) returns the address of the boolean field conf.<name>.
+// For accessing unexported fields.
+func boolFieldAddr(conf *Config, name string) *bool {
 	v := reflect.Indirect(reflect.ValueOf(conf))
-	return (*bool)(v.FieldByName("oldComparableSemantics").Addr().UnsafePointer())
+	return (*bool)(v.FieldByName(name).Addr().UnsafePointer())
 }
 
 // TestManual is for manual testing of a package - either provided

src/go/types/decl.go

@@ -54,7 +54,7 @@ func pathString(path []Object) string {
 // objDecl type-checks the declaration of obj in its respective (file) environment.
 // For the meaning of def, see Checker.definedType, in typexpr.go.
 func (check *Checker) objDecl(obj Object, def *Named) {
-	if trace && obj.Type() == nil {
+	if check.conf.trace && obj.Type() == nil {
 		if check.indent == 0 {
 			fmt.Println() // empty line between top-level objects for readability
 		}
@@ -264,7 +264,7 @@ loop:
 		}
 	}
 
-	if trace {
+	if check.conf.trace {
 		check.trace(obj.Pos(), "## cycle detected: objPath = %s->%s (len = %d)", pathString(cycle), obj.Name(), len(cycle))
 		if tparCycle {
 			check.trace(obj.Pos(), "## cycle contains: generic type in a type parameter list")
@@ -707,7 +707,7 @@ func (check *Checker) declareTypeParams(tparams []*TypeParam, names []*ast.Ident
 		tparams = append(tparams, tpar)
 	}
 
-	if trace && len(names) > 0 {
+	if check.conf.trace && len(names) > 0 {
 		check.trace(names[0].Pos(), "type params = %v", tparams[len(tparams)-len(names):])
 	}
 

src/go/types/errors.go

@@ -266,7 +266,7 @@ func (check *Checker) report(errp *error_) {
 		check.firstErr = err
 	}
 
-	if trace {
+	if check.conf.trace {
 		pos := e.Pos
 		msg := e.Msg
 		check.trace(pos, "ERROR: %s", msg)

src/go/types/expr.go

@@ -1224,7 +1224,7 @@ const (
 // If allowGeneric is set, the operand type may be an uninstantiated
 // parameterized type or function value.
 func (check *Checker) rawExpr(x *operand, e ast.Expr, hint Type, allowGeneric bool) exprKind {
-	if trace {
+	if check.conf.trace {
 		check.trace(e.Pos(), "-- expr %s", e)
 		check.indent++
 		defer func() {

src/go/types/named.go

@@ -581,7 +581,7 @@ func (check *Checker) context() *Context {
 // returning the result. Returns Typ[Invalid] if there was an error.
 func (n *Named) expandUnderlying() Type {
 	check := n.check
-	if check != nil && trace {
+	if check != nil && check.conf.trace {
 		check.trace(n.obj.pos, "-- Named.expandUnderlying %s", n)
 		check.indent++
 		defer func() {

src/go/types/stmt.go

@@ -19,7 +19,7 @@ func (check *Checker) funcBody(decl *declInfo, name string, sig *Signature, body
 		panic("function body not ignored")
 	}
 
-	if trace {
+	if check.conf.trace {
 		check.trace(body.Pos(), "-- %s: %s", name, sig)
 	}
 

src/go/types/subst.go

@@ -204,7 +204,7 @@ func (subst *subster) typ(typ Type) Type {
 	case *Named:
 		// dump is for debugging
 		dump := func(string, ...any) {}
-		if subst.check != nil && trace {
+		if subst.check != nil && subst.check.conf.trace {
 			subst.check.indent++
 			defer func() {
 				subst.check.indent--

src/go/types/typeset.go

@@ -170,7 +170,7 @@ func computeInterfaceTypeSet(check *Checker, pos token.Pos, ityp *Interface) *_T
 		return &topTypeSet
 	}
 
-	if check != nil && trace {
+	if check != nil && check.conf.trace {
 		// Types don't generally have position information.
 		// If we don't have a valid pos provided, try to use
 		// one close enough.

src/go/types/typexpr.go

@@ -214,7 +214,7 @@ func goTypeName(typ Type) string {
 // typInternal drives type checking of types.
 // Must only be called by definedType or genericType.
 func (check *Checker) typInternal(e0 ast.Expr, def *Named) (T Type) {
-	if trace {
+	if check.conf.trace {
 		check.trace(e0.Pos(), "-- type %s", e0)
 		check.indent++
 		defer func() {
@@ -395,7 +395,7 @@ func (check *Checker) typInternal(e0 ast.Expr, def *Named) (T Type) {
 }
 
 func (check *Checker) instantiatedType(ix *typeparams.IndexExpr, def *Named) (res Type) {
-	if trace {
+	if check.conf.trace {
 		check.trace(ix.Pos(), "-- instantiating type %s with %s", ix.X, ix.Indices)
 		check.indent++
 		defer func() {