go/types: report object path in trace mode

For debugging only; disabled (dead code) by default
unless internal constant trace flag is set to true.

For #8699.

Change-Id: Ib7b272c6ac8efacccbbbe24650ef500c5a9ddcf5
Reviewed-on: https://go-review.googlesource.com/115457Reviewed-by: Alan Donovan <adonovan@google.com>

src/go/types/check.go

@@ -160,6 +160,18 @@ func (check *Checker) pop() Object {
 	return obj
 }
 
+// pathString returns a string of the form a->b-> ... ->g for an object path [a, b, ... g].
+func (check *Checker) pathString() string {
+	var s string
+	for i, p := range check.objPath {
+		if i > 0 {
+			s += "->"
+		}
+		s += p.Name()
+	}
+	return s
+}
+
 // NewChecker returns a new Checker instance for a given package.
 // Package files may be added incrementally via checker.Files.
 func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Checker {

src/go/types/decl.go

@@ -158,7 +158,7 @@ func (check *Checker) objDecl(obj Object, def *Named, path []*TypeName) {
 	}
 
 	if trace {
-		check.trace(obj.Pos(), "-- checking %s (path = %s)", obj, pathString(path))
+		check.trace(obj.Pos(), "-- checking %s (path = %s, objPath = %s)", obj, pathString(path), check.pathString())
 		check.indent++
 		defer func() {
 			check.indent--
@@ -208,7 +208,7 @@ func (check *Checker) objDecl(obj Object, def *Named, path []*TypeName) {
 // to the next. For instance, for "type p *p" the object path contains
 // p followed by indir, indicating that there's an indirection *p.
 // Indirections are used to break type cycles.
-var indir = new(TypeName)
+var indir = NewTypeName(token.NoPos, nil, "*", nil)
 
 // typeCycle checks if the cycle starting with obj is valid and
 // reports an error if it is not.

src/go/types/interfaces.go

@@ -144,7 +144,7 @@ func (check *Checker) infoFromTypeLit(scope *Scope, iface *ast.InterfaceType, tn
 	}
 
 	if trace {
-		check.trace(iface.Pos(), "-- collect methods for %v (path = %s)", iface, pathString(path))
+		check.trace(iface.Pos(), "-- collect methods for %v (path = %s, objPath = %s)", iface, pathString(path), check.pathString())
 		check.indent++
 		defer func() {
 			check.indent--