[dev.typeparams] go/types: add some missing APIs for the importer

This is a partial port of CL 319930, containing only changes to
go/types. Importer changes will be made in a separate CL.

The TypeParams APIs are left unexported for now; they will be exported
when they are needed.

Change-Id: I74bd246d4c174cb38f8360d921c733fa03900eab
Reviewed-on: https://go-review.googlesource.com/c/go/+/335143
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

src/go/types/api_test.go

@@ -331,16 +331,16 @@ func TestTypesInfo(t *testing.T) {
 		{broken + `x5; func _() { var x map[string][...]int; x = map[string][...]int{"": {1,2,3}} }`, `x`, `map[string][-1]int`},
 
 		// parameterized functions
-		{genericPkg + `p0; func f[T any](T); var _ = f[int]`, `f`, `func[T₁ interface{}](T₁)`},
+		{genericPkg + `p0; func f[T any](T); var _ = f[int]`, `f`, `func[generic_p0.T₁ interface{}](generic_p0.T₁)`},
 		{genericPkg + `p1; func f[T any](T); var _ = f[int]`, `f[int]`, `func(int)`},
-		{genericPkg + `p2; func f[T any](T); func _() { f(42) }`, `f`, `func[T₁ interface{}](T₁)`},
+		{genericPkg + `p2; func f[T any](T); func _() { f(42) }`, `f`, `func[generic_p2.T₁ interface{}](generic_p2.T₁)`},
 		{genericPkg + `p3; func f[T any](T); func _() { f(42) }`, `f(42)`, `()`},
 
 		// type parameters
 		{genericPkg + `t0; type t[] int; var _ t`, `t`, `generic_t0.t`}, // t[] is a syntax error that is ignored in this test in favor of t
-		{genericPkg + `t1; type t[P any] int; var _ t[int]`, `t`, `generic_t1.t[P₁ interface{}]`},
-		{genericPkg + `t2; type t[P interface{}] int; var _ t[int]`, `t`, `generic_t2.t[P₁ interface{}]`},
-		{genericPkg + `t3; type t[P, Q interface{}] int; var _ t[int, int]`, `t`, `generic_t3.t[P₁, Q₂ interface{}]`},
+		{genericPkg + `t1; type t[P any] int; var _ t[int]`, `t`, `generic_t1.t[generic_t1.P₁ interface{}]`},
+		{genericPkg + `t2; type t[P interface{}] int; var _ t[int]`, `t`, `generic_t2.t[generic_t2.P₁ interface{}]`},
+		{genericPkg + `t3; type t[P, Q interface{}] int; var _ t[int, int]`, `t`, `generic_t3.t[generic_t3.P₁, generic_t3.Q₂ interface{}]`},
 
 		// TODO (rFindley): compare with types2, which resolves the type broken_t4.t[P₁, Q₂ interface{m()}] here
 		{broken + `t4; type t[P, Q interface{ m() }] int; var _ t[int, int]`, `t`, `broken_t4.t`},
@@ -349,7 +349,7 @@ func TestTypesInfo(t *testing.T) {
 		{genericPkg + `g0; type t[P any] int; var x struct{ f t[int] }; var _ = x.f`, `x.f`, `generic_g0.t[int]`},
 
 		// issue 45096
-		{genericPkg + `issue45096; func _[T interface{ ~int8 | ~int16 | ~int32  }](x T) { _ = x < 0 }`, `0`, `T₁`},
+		{genericPkg + `issue45096; func _[T interface{ ~int8 | ~int16 | ~int32  }](x T) { _ = x < 0 }`, `0`, `generic_issue45096.T₁`},
 	}
 
 	for _, test := range tests {

src/go/types/signature.go

@@ -55,12 +55,15 @@ func NewSignature(recv *Var, params, results *Tuple, variadic bool) *Signature {
 // contain methods whose receiver type is a different interface.
 func (s *Signature) Recv() *Var { return s.recv }
 
-// _TParams returns the type parameters of signature s, or nil.
+// TParams returns the type parameters of signature s, or nil.
 func (s *Signature) TParams() []*TypeName { return s.tparams }
 
-// _SetTParams sets the type parameters of signature s.
+// SetTParams sets the type parameters of signature s.
 func (s *Signature) SetTParams(tparams []*TypeName) { s.tparams = tparams }
 
+// SetRParams sets the receiver type params of signature s.
+func (s *Signature) SetRParams(rparams []*TypeName) { s.rparams = rparams }
+
 // Params returns the parameters of signature s, or nil.
 func (s *Signature) Params() *Tuple { return s.params }
 

src/go/types/typeparam.go

@@ -50,7 +50,18 @@ func (check *Checker) newTypeParam(obj *TypeName, index int, bound Type) *TypePa
 	return typ
 }
 
-// TODO(rfindley): types2 to has Index and SetID. Should we add them here?
+// TODO(rfindley): remove or export these placeholder APIs.
+
+// Index returns the index of the type param within its param list.
+func (t *TypeParam) _Index() int {
+	return t.index
+}
+
+// SetId sets the unique id of a type param. Should only be used for type params
+// in imported generic types.
+func (t *TypeParam) _SetId(id uint64) {
+	t.id = id
+}
 
 func (t *TypeParam) Bound() *Interface {
 	// we may not have an interface (error reported elsewhere)

src/go/types/typestring.go

@@ -284,6 +284,13 @@ func writeType(buf *bytes.Buffer, typ Type, qf Qualifier, visited []Type) {
 	case *TypeParam:
 		s := "?"
 		if t.obj != nil {
+			// Optionally write out package for typeparams (like Named).
+			// TODO(rfindley): this is required for import/export, so
+			// we maybe need a separate function that won't be changed
+			// for debugging purposes.
+			if t.obj.pkg != nil {
+				writePackage(buf, t.obj.pkg, qf)
+			}
 			s = t.obj.name
 		}
 		buf.WriteString(s + subscript(t.id))