cmd/compile/internal/types2: eliminate Named.instPos

This is a clean port of CL 349411 from go/types to types2.

Change-Id: Id5fa04c53f286dad263d7ba7911cb49eebf47b0e
Reviewed-on: https://go-review.googlesource.com/c/go/+/350030
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

src/cmd/compile/internal/types2/environment.go

@@ -50,13 +50,6 @@ func (env *Environment) TypeHash(typ Type, targs []Type) string {
 		h.typ(typ)
 	}
 
-	if debug {
-		// there should be no instance markers in type hashes
-		for _, b := range buf.Bytes() {
-			assert(b != instanceMarker)
-		}
-	}
-
 	return strings.Replace(buf.String(), " ", "#", -1) // ReplaceAll is not available in Go1.4
 }
 

src/cmd/compile/internal/types2/errors.go

@@ -246,7 +246,7 @@ func stripAnnotations(s string) string {
 	var b bytes.Buffer
 	for _, r := range s {
 		// strip #'s and subscript digits
-		if r != instanceMarker && !('₀' <= r && r < '₀'+10) { // '₀' == U+2080
+		if r < '₀' || '₀'+10 <= r { // '₀' == U+2080
 			b.WriteRune(r)
 		}
 	}

src/cmd/compile/internal/types2/errors_test.go

@@ -35,7 +35,6 @@ func TestStripAnnotations(t *testing.T) {
 		{"foo", "foo"},
 		{"foo₀", "foo"},
 		{"foo(T₀)", "foo(T)"},
-		{"#foo(T₀)", "foo(T)"},
 	} {
 		got := stripAnnotations(test.in)
 		if got != test.want {

src/cmd/compile/internal/types2/instantiate.go

@@ -118,8 +118,9 @@ func (check *Checker) instance(pos syntax.Pos, typ Type, targs []Type, env *Envi
 		tname := NewTypeName(pos, t.obj.pkg, t.obj.name, nil)
 		named := check.newNamed(tname, t, nil, nil, nil) // methods and tparams are set when named is resolved
 		named.targs = NewTypeList(targs)
-		named.instPos = &pos
-		named.resolver = expandNamed
+		named.resolver = func(env *Environment, n *Named) (*TypeParamList, Type, []*Func) {
+			return expandNamed(env, n, pos)
+		}
 		if env != nil {
 			// It's possible that we've lost a race to add named to the environment.
 			// In this case, use whichever instance is recorded in the environment.

src/cmd/compile/internal/types2/named.go

@@ -17,7 +17,6 @@ type Named struct {
 	orig       *Named         // original, uninstantiated type
 	fromRHS    Type           // type (on RHS of declaration) this *Named type is derived from (for cycle reporting)
 	underlying Type           // possibly a *Named during setup; never a *Named once set up completely
-	instPos    *syntax.Pos    // position information for lazy instantiation, or nil
 	tparams    *TypeParamList // type parameters, or nil
 	targs      *TypeList      // type arguments (after instantiation), or nil
 	methods    []*Func        // methods declared for this type (not the method set of this type); signatures are type-checked lazily
@@ -222,11 +221,11 @@ func (n *Named) setUnderlying(typ Type) {
 
 // expandNamed ensures that the underlying type of n is instantiated.
 // The underlying type will be Typ[Invalid] if there was an error.
-func expandNamed(env *Environment, n *Named) (*TypeParamList, Type, []*Func) {
+func expandNamed(env *Environment, n *Named, instPos syntax.Pos) (*TypeParamList, Type, []*Func) {
 	n.orig.resolve(env)
 
 	var u Type
-	if n.check.validateTArgLen(*n.instPos, n.orig.tparams.Len(), n.targs.Len()) {
+	if n.check.validateTArgLen(instPos, n.orig.tparams.Len(), n.targs.Len()) {
 		// TODO(rfindley): handling an optional Checker and Environment here (and
 		// in subst) feels overly complicated. Can we simplify?
 		if env == nil {
@@ -245,11 +244,10 @@ func expandNamed(env *Environment, n *Named) (*TypeParamList, Type, []*Func) {
 			// shouldn't return that instance from expand.
 			env.typeForHash(h, n)
 		}
-		u = n.check.subst(*n.instPos, n.orig.underlying, makeSubstMap(n.orig.tparams.list(), n.targs.list()), env)
+		u = n.check.subst(instPos, n.orig.underlying, makeSubstMap(n.orig.tparams.list(), n.targs.list()), env)
 	} else {
 		u = Typ[Invalid]
 	}
-	n.instPos = nil
 	return n.orig.tparams, u, n.orig.methods
 }
 

src/cmd/compile/internal/types2/sizeof_test.go

@@ -31,7 +31,7 @@ func TestSizeof(t *testing.T) {
 		{Interface{}, 44, 88},
 		{Map{}, 16, 32},
 		{Chan{}, 12, 24},
-		{Named{}, 72, 136},
+		{Named{}, 68, 128},
 		{TypeParam{}, 28, 48},
 		{term{}, 12, 24},
 		{top{}, 0, 0},

src/cmd/compile/internal/types2/typestring.go

@@ -63,9 +63,6 @@ func WriteSignature(buf *bytes.Buffer, sig *Signature, qf Qualifier) {
 	newTypeWriter(buf, qf).signature(sig)
 }
 
-// instanceMarker is the prefix for an instantiated type in unexpanded form.
-const instanceMarker = '#'
-
 type typeWriter struct {
 	buf  *bytes.Buffer
 	seen map[Type]bool
@@ -245,13 +242,6 @@ func (w *typeWriter) typ(typ Type) {
 		}
 
 	case *Named:
-		// Instance markers indicate unexpanded instantiated
-		// types. Write them to aid debugging, but don't write
-		// them when we need an instance hash: whether a type
-		// is fully expanded or not doesn't matter for identity.
-		if w.env == nil && t.instPos != nil {
-			w.byte(instanceMarker)
-		}
 		w.typePrefix(t)
 		w.typeName(t.obj)
 		if t.targs != nil {