cmd/compile/internal/types2: add Named.SetTParams and Named.Orig methods

Named.SetTParams sets the type parameters for a named type.

Named.Orig returns the original generic type an instantiated
type is derived from. Added a new field orig for that purpose
and renamed the already existing orig field to fromRHS.

Finally, updated various comments.

Change-Id: Ic9d173e42740422d195713d8bdc62a54dc8c5f54
Reviewed-on: https://go-review.googlesource.com/c/go/+/309832
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

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

@@ -333,7 +333,7 @@ func (check *Checker) validType(typ Type, path []Object) typeInfo {
 		switch t.info {
 		case unknown:
 			t.info = marked
-			t.info = check.validType(t.orig, append(path, t.obj)) // only types of current package added to path
+			t.info = check.validType(t.fromRHS, append(path, t.obj)) // only types of current package added to path
 		case marked:
 			// cycle detected
 			for i, tn := range path {
@@ -611,9 +611,8 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *syntax.TypeDecl, def *Named
 	} else {
 		// defined type declaration
 
-		named := &Named{check: check, obj: obj}
+		named := check.newNamed(obj, nil, nil, nil, nil)
 		def.setUnderlying(named)
-		obj.typ = named // make sure recursive type declarations terminate
 
 		if tdecl.TParamList != nil {
 			check.openScope(tdecl, "type parameters")
@@ -622,7 +621,7 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *syntax.TypeDecl, def *Named
 		}
 
 		// determine underlying type of named
-		named.orig = check.definedType(tdecl.Type, named)
+		named.fromRHS = check.definedType(tdecl.Type, named)
 
 		// The underlying type of named may be itself a named type that is
 		// incomplete:
@@ -637,7 +636,7 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *syntax.TypeDecl, def *Named
 		// and which has as its underlying type the named type B.
 		// Determine the (final, unnamed) underlying type by resolving
 		// any forward chain.
-		// TODO(gri) Investigate if we can just use named.origin here
+		// TODO(gri) Investigate if we can just use named.fromRHS here
 		//           and rely on lazy computation of the underlying type.
 		named.underlying = under(named)
 	}

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

@@ -195,7 +195,7 @@ L7 uses var z int`
 	}
 }
 
-// This tests that the package associated with the types.Object.Pkg method
+// This tests that the package associated with the types2.Object.Pkg method
 // is the type's package independent of the order in which the imports are
 // listed in the sources src1, src2 below.
 // The actual issue is in go/internal/gcimporter which has a corresponding

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

@@ -126,8 +126,8 @@ func (s sanitizer) typ(typ Type) Type {
 		}
 
 	case *Named:
-		if orig := s.typ(t.orig); orig != t.orig {
+		if orig := s.typ(t.fromRHS); orig != t.fromRHS {
-			t.orig = orig
+			t.fromRHS = orig
 		}
 		if under := s.typ(t.underlying); under != t.underlying {
 			t.underlying = under

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

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// This file tests types.Check by using it to
+// This file tests types2.Check by using it to
 // typecheck the standard library and tests.
 
 package types2_test

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

@@ -385,8 +385,7 @@ func (subst *subster) typ(typ Type) Type {
 
 		// create a new named type and populate caches to avoid endless recursion
 		tname := NewTypeName(subst.pos, t.obj.pkg, t.obj.name, nil)
-		named := subst.check.NewNamed(tname, t.underlying, t.methods) // method signatures are updated lazily
+		named := subst.check.newNamed(tname, t, t.underlying, t.tparams, t.methods) // method signatures are updated lazily
-		named.tparams = t.tparams                                     // new type is still parameterized
 		named.targs = new_targs
 		subst.check.typMap[h] = named
 		subst.cache[t] = named
@@ -394,7 +393,7 @@ func (subst *subster) typ(typ Type) Type {
 		// do the substitution
 		dump(">>> subst %s with %s (new: %s)", t.underlying, subst.smap, new_targs)
 		named.underlying = subst.typOrNil(t.underlying)
-		named.orig = named.underlying // for cycle detection (Checker.validType)
+		named.fromRHS = named.underlying // for cycle detection (Checker.validType)
 
 		return named
 

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

@@ -224,10 +224,10 @@ func NewSignature(recv *Var, params, results *Tuple, variadic bool) *Signature {
 	if variadic {
 		n := params.Len()
 		if n == 0 {
-			panic("types.NewSignature: variadic function must have at least one parameter")
+			panic("types2.NewSignature: variadic function must have at least one parameter")
 		}
 		if _, ok := params.At(n - 1).typ.(*Slice); !ok {
-			panic("types.NewSignature: variadic parameter must be of unnamed slice type")
+			panic("types2.NewSignature: variadic parameter must be of unnamed slice type")
 		}
 	}
 	return &Signature{recv: recv, params: params, results: results, variadic: variadic}
@@ -645,12 +645,15 @@ func (c *Chan) Dir() ChanDir { return c.dir }
 // Elem returns the element type of channel c.
 func (c *Chan) Elem() Type { return c.elem }
 
+// TODO(gri) Clean up Named struct below; specifically the fromRHS field (can we use underlying?).
+
 // A Named represents a named (defined) type.
 type Named struct {
 	check      *Checker    // for Named.under implementation
 	info       typeInfo    // for cycle detection
 	obj        *TypeName   // corresponding declared object
-	orig       Type        // type (on RHS of declaration) this *Named type is derived of (for cycle reporting)
+	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
 	tparams    []*TypeName // type parameters, or nil
 	targs      []Type      // type arguments (after instantiation), or nil
@@ -662,17 +665,17 @@ type Named struct {
 // The underlying type must not be a *Named.
 func NewNamed(obj *TypeName, underlying Type, methods []*Func) *Named {
 	if _, ok := underlying.(*Named); ok {
-		panic("types.NewNamed: underlying type must not be *Named")
+		panic("types2.NewNamed: underlying type must not be *Named")
 	}
-	typ := &Named{obj: obj, orig: underlying, underlying: underlying, methods: methods}
+	return (*Checker)(nil).newNamed(obj, nil, underlying, nil, methods)
-	if obj.typ == nil {
-		obj.typ = typ
-	}
-	return typ
 }
 
-func (check *Checker) NewNamed(obj *TypeName, underlying Type, methods []*Func) *Named {
+// newNamed is like NewNamed but with a *Checker receiver and additional orig argument.
-	typ := &Named{check: check, obj: obj, orig: underlying, underlying: underlying, methods: methods}
+func (check *Checker) newNamed(obj *TypeName, orig *Named, underlying Type, tparams []*TypeName, methods []*Func) *Named {
+	typ := &Named{check: check, obj: obj, orig: orig, fromRHS: underlying, underlying: underlying, tparams: tparams, methods: methods}
+	if typ.orig == nil {
+		typ.orig = typ
+	}
 	if obj.typ == nil {
 		obj.typ = typ
 	}
@@ -682,6 +685,10 @@ func (check *Checker) NewNamed(obj *TypeName, underlying Type, methods []*Func)
 // Obj returns the type name for the named type t.
 func (t *Named) Obj() *TypeName { return t.obj }
 
+// Orig returns the original generic type an instantiated type is derived from.
+// If t is not an instantiated type, the result is t.
+func (t *Named) Orig() *Named { return t.orig }
+
 // TODO(gri) Come up with a better representation and API to distinguish
 //           between parameterized instantiated and non-instantiated types.
 
@@ -689,10 +696,13 @@ func (t *Named) Obj() *TypeName { return t.obj }
 // The result is non-nil for an (originally) parameterized type even if it is instantiated.
 func (t *Named) TParams() []*TypeName { return t.tparams }
 
+// SetTParams sets the type parameters of the named type t.
+func (t *Named) SetTParams(tparams []*TypeName) { t.tparams = tparams }
+
 // TArgs returns the type arguments after instantiation of the named type t, or nil if not instantiated.
 func (t *Named) TArgs() []Type { return t.targs }
 
-// SetTArgs sets the type arguments of Named.
+// SetTArgs sets the type arguments of the named type t.
 func (t *Named) SetTArgs(args []Type) { t.targs = args }
 
 // NumMethods returns the number of explicit methods whose receiver is named type t.
@@ -704,10 +714,10 @@ func (t *Named) Method(i int) *Func { return t.methods[i] }
 // SetUnderlying sets the underlying type and marks t as complete.
 func (t *Named) SetUnderlying(underlying Type) {
 	if underlying == nil {
-		panic("types.Named.SetUnderlying: underlying type must not be nil")
+		panic("types2.Named.SetUnderlying: underlying type must not be nil")
 	}
 	if _, ok := underlying.(*Named); ok {
-		panic("types.Named.SetUnderlying: underlying type must not be *Named")
+		panic("types2.Named.SetUnderlying: underlying type must not be *Named")
 	}
 	t.underlying = underlying
 }
@@ -731,9 +741,9 @@ func nextId() uint64 { return uint64(atomic.AddUint32(&lastId, 1)) }
 // A TypeParam represents a type parameter type.
 type TypeParam struct {
 	check *Checker  // for lazy type bound completion
-	id    uint64    // unique id
+	id    uint64    // unique id, for debugging only
 	obj   *TypeName // corresponding type name
-	index int       // parameter index
+	index int       // type parameter index in source order, starting at 0
 	bound Type      // *Named or *Interface; underlying type is always *Interface
 }
 

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

@@ -431,9 +431,9 @@ func (check *Checker) funcType(sig *Signature, recvPar *syntax.Field, tparams []
 }
 
 // goTypeName returns the Go type name for typ and
-// removes any occurrences of "types." from that name.
+// removes any occurrences of "types2." from that name.
 func goTypeName(typ Type) string {
-	return strings.Replace(fmt.Sprintf("%T", typ), "types.", "", -1) // strings.ReplaceAll is not available in Go 1.4
+	return strings.Replace(fmt.Sprintf("%T", typ), "types2.", "", -1) // strings.ReplaceAll is not available in Go 1.4
 }
 
 // typInternal drives type checking of types.