go/types, types2: implement Alias proposal (export API)

[gostls13.git] / src / go / types / check.go

diff --git a/src/go/types/check.go b/src/go/types/check.go
index 28515aea239f42bccb4423cdd0920f3efb3a1be0..0feea6dfeba678815a8559497e643152439a79a1 100644 (file)
--- a/src/go/types/check.go
+++ b/src/go/types/check.go
@@ -12,6 +12,7 @@ import (
        "go/ast"
        "go/constant"
        "go/token"
+       "internal/godebug"
        "internal/goversion"
        . "internal/types/errors"
 )
@@ -22,6 +23,9 @@ var nopos token.Pos
 // debugging/development support
 const debug = false // leave on during development
 
+// gotypesalias controls the use of Alias types
+var gotypesalias = godebug.New("gotypesalias")
+
 // exprInfo stores information about an untyped expression.
 type exprInfo struct {
        isLhs bool // expression is lhs operand of a shift with delayed type-check
@@ -90,10 +94,16 @@ type actionDesc struct {
 }
 
 // A Checker maintains the state of the type checker.
-// It must be created with NewChecker.
+// It must be created with [NewChecker].
 type Checker struct {
        // package information
        // (initialized by NewChecker, valid for the life-time of checker)
+
+       // If EnableAlias is set, alias declarations produce an Alias type.
+       // Otherwise the alias information is only in the type name, which
+       // points directly to the actual (aliased) type.
+       enableAlias bool
+
        conf *Config
        ctxt *Context // context for de-duplicating instances
        fset *token.FileSet
@@ -154,9 +164,14 @@ func (check *Checker) addDeclDep(to Object) {
        from.addDep(to)
 }
 
+// Note: The following three alias-related functions are only used
+//       when Alias types are not enabled.
+
 // brokenAlias records that alias doesn't have a determined type yet.
 // It also sets alias.typ to Typ[Invalid].
+// Not used if check.enableAlias is set.
 func (check *Checker) brokenAlias(alias *TypeName) {
+       assert(!check.enableAlias)
        if check.brokenAliases == nil {
                check.brokenAliases = make(map[*TypeName]bool)
        }
@@ -166,13 +181,15 @@ func (check *Checker) brokenAlias(alias *TypeName) {
 
 // validAlias records that alias has the valid type typ (possibly Typ[Invalid]).
 func (check *Checker) validAlias(alias *TypeName, typ Type) {
+       assert(!check.enableAlias)
        delete(check.brokenAliases, alias)
        alias.typ = typ
 }
 
 // isBrokenAlias reports whether alias doesn't have a determined type yet.
 func (check *Checker) isBrokenAlias(alias *TypeName) bool {
-       return !isValid(alias.typ) && check.brokenAliases[alias]
+       assert(!check.enableAlias)
+       return check.brokenAliases[alias]
 }
 
 func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
@@ -221,8 +238,8 @@ func (check *Checker) needsCleanup(c cleaner) {
        check.cleaners = append(check.cleaners, c)
 }
 
-// NewChecker returns a new Checker instance for a given package.
-// Package files may be added incrementally via checker.Files.
+// NewChecker returns a new [Checker] instance for a given package.
+// [Package] files may be added incrementally via checker.Files.
 func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Checker {
        // make sure we have a configuration
        if conf == nil {
@@ -241,13 +258,14 @@ func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Ch
        // (previously, pkg.goVersion was mutated here: go.dev/issue/61212)
 
        return &Checker{
-               conf:   conf,
-               ctxt:   conf.Context,
-               fset:   fset,
-               pkg:    pkg,
-               Info:   info,
-               objMap: make(map[Object]*declInfo),
-               impMap: make(map[importKey]*Package),
+               enableAlias: gotypesalias.Value() == "1",
+               conf:        conf,
+               ctxt:        conf.Context,
+               fset:        fset,
+               pkg:         pkg,
+               Info:        info,
+               objMap:      make(map[Object]*declInfo),
+               impMap:      make(map[importKey]*Package),
        }
 }
 
@@ -289,7 +307,7 @@ func (check *Checker) initFiles(files []*ast.File) {
 
        // collect file versions
        for _, file := range check.files {
-               check.recordFileVersion(file, check.conf.GoVersion)
+               check.recordFileVersion(file, check.conf.GoVersion) // record package version (possibly zero version)
                if v, _ := parseGoVersion(file.GoVersion); v.major > 0 {
                        if v.equal(check.version) {
                                continue
@@ -634,7 +652,7 @@ func (check *Checker) recordScope(node ast.Node, scope *Scope) {
 }
 
 func (check *Checker) recordFileVersion(file *ast.File, version string) {
-       if m := check._FileVersions; m != nil {
+       if m := check.FileVersions; m != nil {
                m[file] = version
        }
 }