go/types: add NewTypeParamList, NewTypeList

Fixes #79603

Change-Id: I04b160a82aed7e6d83051f8e05a4ccad7d97c297
Reviewed-on: https://go-review.googlesource.com/c/go/+/792520
Reviewed-by: Alan Donovan <adonovan@google.com>
Auto-Submit: Alan Donovan <adonovan@google.com>
Reviewed-by: Mark Freeman <mark@golang.org>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

api/next/79603.txt

@@ -0,0 +1,2 @@
+pkg go/types, func NewTypeList([]Type) *TypeList #79603
+pkg go/types, func NewTypeParamList([]*TypeParam) *TypeParamList #79603

doc/next/6-stdlib/99-minor/go/types/79603.md

@@ -0,0 +1,3 @@
+Added [NewTypeList] and [NewTypeParamList] constructors to
+create [TypeList] and [TypeParamList] instances
+from slices of their respective element types.

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

@@ -165,7 +165,7 @@ func (check *Checker) newAliasInstance(pos syntax.Pos, orig *Alias, targs []Type
 	res := check.newAlias(obj, rhs)
 	res.orig = orig
 	res.tparams = orig.tparams
-	res.targs = newTypeList(targs)
+	res.targs = NewTypeList(targs)
 	// Ensure that res.actual is set before returning an instance constructed
 	// outside of package type checking (e.g. via types.Instantiate). When check != nil,
 	// res was added to check.cleanups by newAlias and will be cleaned up at the end

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

@@ -342,7 +342,7 @@ func (check *Checker) newNamedInstance(pos syntax.Pos, orig *Named, targs []Type
 	assert(len(targs) > 0)
 
 	obj := NewTypeName(pos, orig.obj.pkg, orig.obj.name, nil)
-	inst := &instance{orig: orig, targs: newTypeList(targs)}
+	inst := &instance{orig: orig, targs: NewTypeList(targs)}
 
 	// Only pass the expanding context to the new instance if their packages
 	// match. Since type reference cycles are only possible within a single

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

@@ -141,14 +141,14 @@ func (check *Checker) recordInstance(expr syntax.Expr, targs []Type, typ Type) {
 				copy.recv = pars.vars[0]
 				pars.vars = pars.vars[1:]
 				copy.params = &pars
-				m[ident] = Instance{newTypeList(targs), &copy}
+				m[ident] = Instance{NewTypeList(targs), &copy}
 				return
 			}
 			copy.recv = sig.recvold
-			m[ident] = Instance{newTypeList(targs), &copy}
+			m[ident] = Instance{NewTypeList(targs), &copy}
 			return
 		}
-		m[ident] = Instance{newTypeList(targs), typ}
+		m[ident] = Instance{NewTypeList(targs), typ}
 	}
 }
 

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

@@ -9,6 +9,15 @@ import "bytes"
 // TypeParamList holds a list of type parameters.
 type TypeParamList struct{ tparams []*TypeParam }
 
+// NewTypeParamList returns a new TypeParamList
+// with the type parameters in list.
+func NewTypeParamList(list []*TypeParam) *TypeParamList {
+	if len(list) == 0 {
+		return nil
+	}
+	return &TypeParamList{list}
+}
+
 // Len returns the number of type parameters in the list.
 // It is safe to call on a nil receiver.
 func (l *TypeParamList) Len() int { return len(l.list()) }
@@ -42,8 +51,8 @@ func (l *TypeParamList) String() string {
 // TypeList holds a list of types.
 type TypeList struct{ types []Type }
 
-// newTypeList returns a new TypeList with the types in list.
-func newTypeList(list []Type) *TypeList {
+// NewTypeList returns a new TypeList with the types in list.
+func NewTypeList(list []Type) *TypeList {
 	if len(list) == 0 {
 		return nil
 	}

src/go/types/alias.go

@@ -168,7 +168,7 @@ func (check *Checker) newAliasInstance(pos token.Pos, orig *Alias, targs []Type,
 	res := check.newAlias(obj, rhs)
 	res.orig = orig
 	res.tparams = orig.tparams
-	res.targs = newTypeList(targs)
+	res.targs = NewTypeList(targs)
 	// Ensure that res.actual is set before returning an instance constructed
 	// outside of package type checking (e.g. via types.Instantiate). When check != nil,
 	// res was added to check.cleanups by newAlias and will be cleaned up at the end

src/go/types/named.go

@@ -345,7 +345,7 @@ func (check *Checker) newNamedInstance(pos token.Pos, orig *Named, targs []Type,
 	assert(len(targs) > 0)
 
 	obj := NewTypeName(pos, orig.obj.pkg, orig.obj.name, nil)
-	inst := &instance{orig: orig, targs: newTypeList(targs)}
+	inst := &instance{orig: orig, targs: NewTypeList(targs)}
 
 	// Only pass the expanding context to the new instance if their packages
 	// match. Since type reference cycles are only possible within a single

src/go/types/recording.go

@@ -144,14 +144,14 @@ func (check *Checker) recordInstance(expr ast.Expr, targs []Type, typ Type) {
 				copy.recv = pars.vars[0]
 				pars.vars = pars.vars[1:]
 				copy.params = &pars
-				m[ident] = Instance{newTypeList(targs), &copy}
+				m[ident] = Instance{NewTypeList(targs), &copy}
 				return
 			}
 			copy.recv = sig.recvold
-			m[ident] = Instance{newTypeList(targs), &copy}
+			m[ident] = Instance{NewTypeList(targs), &copy}
 			return
 		}
-		m[ident] = Instance{newTypeList(targs), typ}
+		m[ident] = Instance{NewTypeList(targs), typ}
 	}
 }
 

src/go/types/typelists.go

@@ -12,6 +12,15 @@ import "bytes"
 // TypeParamList holds a list of type parameters.
 type TypeParamList struct{ tparams []*TypeParam }
 
+// NewTypeParamList returns a new TypeParamList
+// with the type parameters in list.
+func NewTypeParamList(list []*TypeParam) *TypeParamList {
+	if len(list) == 0 {
+		return nil
+	}
+	return &TypeParamList{list}
+}
+
 // Len returns the number of type parameters in the list.
 // It is safe to call on a nil receiver.
 func (l *TypeParamList) Len() int { return len(l.list()) }
@@ -45,8 +54,8 @@ func (l *TypeParamList) String() string {
 // TypeList holds a list of types.
 type TypeList struct{ types []Type }
 
-// newTypeList returns a new TypeList with the types in list.
-func newTypeList(list []Type) *TypeList {
+// NewTypeList returns a new TypeList with the types in list.
+func NewTypeList(list []Type) *TypeList {
 	if len(list) == 0 {
 		return nil
 	}