[dev.typeparams] cmd/compile/internal/types2: remove support for type parameter pointer designation

An earlier version of the draft design supported pointer designation for
type parameters. Remove related code since we don't need it anymore.

Change-Id: I0d9e8c5f02a9a6745ff7ee15b8267a99ab1529e1
Reviewed-on: https://go-review.googlesource.com/c/go/+/273327
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/builtins.go

@@ -727,7 +727,7 @@ func (check *Checker) applyTypeFunc(f func(Type) Type, x Type) Type {
 
 		// construct a suitable new type parameter
 		tpar := NewTypeName(nopos, nil /* = Universe pkg */, "<type parameter>", nil)
-		ptyp := check.NewTypeParam(tp.ptr, tpar, 0, &emptyInterface) // assigns type to tpar as a side-effect
+		ptyp := check.NewTypeParam(tpar, 0, &emptyInterface) // assigns type to tpar as a side-effect
 		tsum := NewSum(rtypes)
 		ptyp.bound = &Interface{types: tsum, allMethods: markComplete, allTypes: tsum}
 

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

@@ -734,15 +734,9 @@ func (check *Checker) collectTypeParams(list []*syntax.Field) (tparams []*TypeNa
 }
 
 func (check *Checker) declareTypeParam(tparams []*TypeName, name *syntax.Name) []*TypeName {
-	var ptr bool
-	nstr := name.Value
-	if len(nstr) > 0 && nstr[0] == '*' {
-		ptr = true
-		nstr = nstr[1:]
-	}
-	tpar := NewTypeName(name.Pos(), check.pkg, nstr, nil)
-	check.NewTypeParam(ptr, tpar, len(tparams), &emptyInterface) // assigns type to tpar as a side-effect
-	check.declare(check.scope, name, tpar, check.scope.pos)      // TODO(gri) check scope position
+	tpar := NewTypeName(name.Pos(), check.pkg, name.Value, nil)
+	check.NewTypeParam(tpar, len(tparams), &emptyInterface) // assigns type to tpar as a side-effect
+	check.declare(check.scope, name, tpar, check.scope.pos) // TODO(gri) check scope position
 	tparams = append(tparams, tpar)
 
 	if check.conf.Trace {

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

@@ -222,7 +222,7 @@ func (check *Checker) rawLookupFieldOrMethod(T Type, addressable bool, pkg *Pack
 			//        is shorthand for (&x).m()".
 			if f, _ := obj.(*Func); f != nil {
 				// determine if method has a pointer receiver
-				hasPtrRecv := tpar == nil && ptrRecv(f) || tpar != nil && tpar.ptr
+				hasPtrRecv := tpar == nil && ptrRecv(f)
 				if hasPtrRecv && !indirect && !addressable {
 					return nil, nil, true // pointer/addressable receiver required
 				}

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

@@ -143,27 +143,14 @@ func (check *Checker) instantiate(pos syntax.Pos, typ Type, targs []Type, poslis
 		// - check only if we have methods
 		check.completeInterface(nopos, iface)
 		if len(iface.allMethods) > 0 {
-			// If the type argument is a type parameter itself, its pointer designation
-			// must match the pointer designation of the callee's type parameter.
 			// If the type argument is a pointer to a type parameter, the type argument's
 			// method set is empty.
 			// TODO(gri) is this what we want? (spec question)
-			if tparg := targ.TypeParam(); tparg != nil {
-				if tparg.ptr != tpar.ptr {
-					check.errorf(pos, "pointer designation mismatch")
-					break
-				}
-			} else if base, isPtr := deref(targ); isPtr && base.TypeParam() != nil {
+			if base, isPtr := deref(targ); isPtr && base.TypeParam() != nil {
 				check.errorf(pos, "%s has no methods", targ)
 				break
 			}
-			// If a type parameter is marked as a pointer type, the type bound applies
-			// to a pointer of the type argument.
-			actual := targ
-			if tpar.ptr {
-				actual = NewPointer(targ)
-			}
-			if m, wrong := check.missingMethod(actual, iface, true); m != nil {
+			if m, wrong := check.missingMethod(targ, iface, true); m != nil {
 				// TODO(gri) needs to print updated name to avoid major confusion in error message!
 				//           (print warning for now)
 				// check.softErrorf(pos, "%s does not satisfy %s (warning: name not updated) = %s (missing method %s)", targ, tpar.bound, iface, m)

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

@@ -832,7 +832,6 @@ func (t *Named) AddMethod(m *Func) {
 type TypeParam struct {
 	check *Checker  // for lazy type bound completion
 	id    uint64    // unique id
-	ptr   bool      // pointer designation
 	obj   *TypeName // corresponding type name
 	index int       // parameter index
 	bound Type      // *Named or *Interface; underlying type is always *Interface
@@ -840,9 +839,9 @@ type TypeParam struct {
 }
 
 // NewTypeParam returns a new TypeParam.
-func (check *Checker) NewTypeParam(ptr bool, obj *TypeName, index int, bound Type) *TypeParam {
+func (check *Checker) NewTypeParam(obj *TypeName, index int, bound Type) *TypeParam {
 	assert(bound != nil)
-	typ := &TypeParam{check: check, id: check.nextId, ptr: ptr, obj: obj, index: index, bound: bound}
+	typ := &TypeParam{check: check, id: check.nextId, obj: obj, index: index, bound: bound}
 	check.nextId++
 	if obj.typ == nil {
 		obj.typ = typ

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

@@ -350,9 +350,6 @@ func writeTParamList(buf *bytes.Buffer, list []*TypeName, qf Qualifier, visited
 		prev = b
 
 		if t, _ := p.typ.(*TypeParam); t != nil {
-			if t.ptr {
-				buf.WriteByte('*')
-			}
 			writeType(buf, t, qf, visited)
 		} else {
 			buf.WriteString(p.name)

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

@@ -307,12 +307,8 @@ func (check *Checker) funcType(sig *Signature, recvPar *syntax.Field, tparams []
 			// - only do this if we have the right number (otherwise an error is reported elsewhere)
 			if len(sig.rparams) == len(recvTParams) {
 				// We have a list of *TypeNames but we need a list of Types.
-				// While creating this list, also update type parameter pointer designation
-				// for each (*TypeParam) list entry, by copying the information from the
-				// receiver base type's type parameters.
 				list := make([]Type, len(sig.rparams))
 				for i, t := range sig.rparams {
-					t.typ.(*TypeParam).ptr = recvTParams[i].typ.(*TypeParam).ptr
 					list[i] = t.typ
 				}
 				for i, tname := range sig.rparams {