cmd/compile/internal/types2: use an identifier map rather than isubst for recv type params
This is a port of CL 354643 from go/types to types2 with adjustments:
- use of syntax rather than go/ast package as needed
- adjustments due to the different code for type parameter declarations
- rename of Checker.rparamMap to Checker.recvTParamMap, which seems clearer
Change-Id: I5311a0c05a13c6b87ea1422b250b90c3d05c5dce
Reviewed-on: https://go-review.googlesource.com/c/go/+/354693
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
diff --git a/src/cmd/compile/internal/types2/check.go b/src/cmd/compile/internal/types2/check.go
index 5957518..d89ec3d 100644
--- a/src/cmd/compile/internal/types2/check.go
+++ b/src/cmd/compile/internal/types2/check.go
@@ -100,9 +100,10 @@
// information collected during type-checking of a set of package files
// (initialized by Files, valid only for the duration of check.Files;
// maps and lists are allocated on demand)
- files []*syntax.File // list of package files
- imports []*PkgName // list of imported packages
- dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
+ files []*syntax.File // list of package files
+ imports []*PkgName // list of imported packages
+ dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
+ recvTParamMap map[*syntax.Name]*TypeParam // maps blank receiver type parameters to their type
firstErr error // first error encountered
methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
@@ -292,6 +293,7 @@
check.dotImportMap = nil
check.pkgPathMap = nil
check.seenPkgMap = nil
+ check.recvTParamMap = nil
// TODO(gri) There's more memory we should release at this point.
diff --git a/src/cmd/compile/internal/types2/signature.go b/src/cmd/compile/internal/types2/signature.go
index 5ea3a05..604d0c9 100644
--- a/src/cmd/compile/internal/types2/signature.go
+++ b/src/cmd/compile/internal/types2/signature.go
@@ -4,10 +4,7 @@
package types2
-import (
- "cmd/compile/internal/syntax"
- "fmt"
-)
+import "cmd/compile/internal/syntax"
// ----------------------------------------------------------------------------
// API
@@ -105,39 +102,33 @@
sig.scope = check.scope
defer check.closeScope()
- var recvTyp syntax.Expr // rewritten receiver type; valid if != nil
if recvPar != nil {
// collect generic receiver type parameters, if any
// - a receiver type parameter is like any other type parameter, except that it is declared implicitly
// - the receiver specification acts as local declaration for its type parameters, which may be blank
_, rname, rparams := check.unpackRecv(recvPar.Type, true)
if len(rparams) > 0 {
- // Blank identifiers don't get declared and regular type-checking of the instantiated
- // parameterized receiver type expression fails in Checker.collectParams of receiver.
- // Identify blank type parameters and substitute each with a unique new identifier named
- // "n_" (where n is the parameter index) and which cannot conflict with any user-defined
- // name.
- var smap map[*syntax.Name]*syntax.Name // substitution map from "_" to "!n" identifiers
+ tparams := make([]*TypeParam, len(rparams))
+ for i, rparam := range rparams {
+ tparams[i] = check.declareTypeParam(rparam)
+ }
+ sig.rparams = bindTParams(tparams)
+ // Blank identifiers don't get declared, so naive type-checking of the
+ // receiver type expression would fail in Checker.collectParams below,
+ // when Checker.ident cannot resolve the _ to a type.
+ //
+ // Checker.recvTParamMap maps these blank identifiers to their type parameter
+ // types, so that they may be resolved in Checker.ident when they fail
+ // lookup in the scope.
for i, p := range rparams {
if p.Value == "_" {
- new := *p
- new.Value = fmt.Sprintf("%d_", i)
- rparams[i] = &new // use n_ identifier instead of _ so it can be looked up
- if smap == nil {
- smap = make(map[*syntax.Name]*syntax.Name)
+ tpar := sig.rparams.At(i)
+ if check.recvTParamMap == nil {
+ check.recvTParamMap = make(map[*syntax.Name]*TypeParam)
}
- smap[p] = &new
+ check.recvTParamMap[p] = tpar
}
}
- if smap != nil {
- // blank identifiers were found => use rewritten receiver type
- recvTyp = isubst(recvPar.Type, smap)
- }
- rlist := make([]*TypeParam, len(rparams))
- for i, rparam := range rparams {
- rlist[i] = check.declareTypeParam(rparam)
- }
- sig.rparams = bindTParams(rlist)
// determine receiver type to get its type parameters
// and the respective type parameter bounds
var recvTParams []*TypeParam
@@ -186,10 +177,10 @@
scope := NewScope(check.scope, nopos, nopos, "function body (temp. scope)")
var recvList []*Var // TODO(gri) remove the need for making a list here
if recvPar != nil {
- recvList, _ = check.collectParams(scope, []*syntax.Field{recvPar}, recvTyp, false) // use rewritten receiver type, if any
+ recvList, _ = check.collectParams(scope, []*syntax.Field{recvPar}, false) // use rewritten receiver type, if any
}
- params, variadic := check.collectParams(scope, ftyp.ParamList, nil, true)
- results, _ := check.collectParams(scope, ftyp.ResultList, nil, false)
+ params, variadic := check.collectParams(scope, ftyp.ParamList, true)
+ results, _ := check.collectParams(scope, ftyp.ResultList, false)
scope.Squash(func(obj, alt Object) {
var err error_
err.errorf(obj, "%s redeclared in this block", obj.Name())
@@ -281,8 +272,8 @@
}
// collectParams declares the parameters of list in scope and returns the corresponding
-// variable list. If type0 != nil, it is used instead of the first type in list.
-func (check *Checker) collectParams(scope *Scope, list []*syntax.Field, type0 syntax.Expr, variadicOk bool) (params []*Var, variadic bool) {
+// variable list.
+func (check *Checker) collectParams(scope *Scope, list []*syntax.Field, variadicOk bool) (params []*Var, variadic bool) {
if list == nil {
return
}
@@ -296,9 +287,6 @@
// type-check type of grouped fields only once
if ftype != prev {
prev = ftype
- if i == 0 && type0 != nil {
- ftype = type0
- }
if t, _ := ftype.(*syntax.DotsType); t != nil {
ftype = t.Elem
if variadicOk && i == len(list)-1 {
@@ -348,61 +336,3 @@
return
}
-
-// isubst returns an x with identifiers substituted per the substitution map smap.
-// isubst only handles the case of (valid) method receiver type expressions correctly.
-func isubst(x syntax.Expr, smap map[*syntax.Name]*syntax.Name) syntax.Expr {
- switch n := x.(type) {
- case *syntax.Name:
- if alt := smap[n]; alt != nil {
- return alt
- }
- // case *syntax.StarExpr:
- // X := isubst(n.X, smap)
- // if X != n.X {
- // new := *n
- // new.X = X
- // return &new
- // }
- case *syntax.Operation:
- if n.Op == syntax.Mul && n.Y == nil {
- X := isubst(n.X, smap)
- if X != n.X {
- new := *n
- new.X = X
- return &new
- }
- }
- case *syntax.IndexExpr:
- Index := isubst(n.Index, smap)
- if Index != n.Index {
- new := *n
- new.Index = Index
- return &new
- }
- case *syntax.ListExpr:
- var elems []syntax.Expr
- for i, elem := range n.ElemList {
- new := isubst(elem, smap)
- if new != elem {
- if elems == nil {
- elems = make([]syntax.Expr, len(n.ElemList))
- copy(elems, n.ElemList)
- }
- elems[i] = new
- }
- }
- if elems != nil {
- new := *n
- new.ElemList = elems
- return &new
- }
- case *syntax.ParenExpr:
- return isubst(n.X, smap) // no need to keep parentheses
- default:
- // Other receiver type expressions are invalid.
- // It's fine to ignore those here as they will
- // be checked elsewhere.
- }
- return x
-}
diff --git a/src/cmd/compile/internal/types2/typexpr.go b/src/cmd/compile/internal/types2/typexpr.go
index 62cfda8..746fe78 100644
--- a/src/cmd/compile/internal/types2/typexpr.go
+++ b/src/cmd/compile/internal/types2/typexpr.go
@@ -28,7 +28,15 @@
switch obj {
case nil:
if e.Value == "_" {
- check.error(e, "cannot use _ as value or type")
+ // Blank identifiers are never declared, but the current identifier may
+ // be a placeholder for a receiver type parameter. In this case we can
+ // resolve its type and object from Checker.recvTParamMap.
+ if tpar := check.recvTParamMap[e]; tpar != nil {
+ x.mode = typexpr
+ x.typ = tpar
+ } else {
+ check.error(e, "cannot use _ as value or type")
+ }
} else {
if check.conf.CompilerErrorMessages {
check.errorf(e, "undefined: %s", e.Value)
