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[dev.typeparams] cmd/compile: implement generic type switches

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Add a new dynamicType node, which is used as a case entry when
the type being switched to is generic.

Change-Id: Ice77c6f224b8fdd3ff574fdf4a8ea5f6c7ddbe75
Reviewed-on: https://go-review.googlesource.com/c/go/+/339429
Trust: Keith Randall <khr@golang.org>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>
This commit is contained in:
Keith Randall 2021-08-03 08:10:17 -07:00
parent 57668b84ff
commit ca3c6985cd
21 changed files with 342 additions and 18 deletions
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50
src/cmd/compile/internal/noder/stencil.go
View file

@ -1140,6 +1140,38 @@ func (subst *subster) node(n ir.Node) ir.Node {
m = ir.NewDynamicTypeAssertExpr(dt.Pos(), op, dt.X, rt)
m.SetType(dt.Type())
m.SetTypecheck(1)
case ir.OCASE:
if _, ok := x.(*ir.CommClause); ok {
// This is not a type switch. TODO: Should we use an OSWITCH case here instead of OCASE?
break
}
x := x.(*ir.CaseClause)
m := m.(*ir.CaseClause)
for i, c := range x.List {
if c.Op() == ir.OTYPE && c.Type().HasTParam() {
// Use a *runtime._type for the dynamic type.
ix := findDictType(subst.info, c.Type())
assert(ix >= 0)
dt := ir.NewDynamicType(c.Pos(), getDictionaryEntry(c.Pos(), subst.info.dictParam, ix, subst.info.dictLen))
// For type switch from nonemoty interfaces to non-interfaces, we need an itab as well.
if _, ok := subst.info.gfInfo.type2switchType[c]; ok {
// Type switch from nonempty interface. We need a *runtime.itab
// for the dynamic type.
ix := -1
for i, ic := range subst.info.gfInfo.itabConvs {
if ic == c {
ix = subst.info.startItabConv + i
break
}
}
assert(ix >= 0)
dt.ITab = getDictionaryEntry(c.Pos(), subst.info.dictParam, ix, subst.info.dictLen)
}
typed(m.List[i].Type(), dt)
m.List[i] = dt
}
}
}
return m
}
@ -1483,6 +1515,9 @@ func (g *irgen) finalizeSyms() {
case ir.OCONVIFACE:
srctype = subst.Typ(n.(*ir.ConvExpr).X.Type())
dsttype = subst.Typ(n.Type())
case ir.OTYPE:
srctype = subst.Typ(n.Type())
dsttype = subst.Typ(info.type2switchType[n])
default:
base.Fatalf("itab entry with unknown op %s", n.Op())
}
@ -1652,6 +1687,21 @@ func (g *irgen) getGfInfo(gn *ir.Name) *gfInfo {
ir.Visit(n1, visitFunc)
}
}
if n.Op() == ir.OSWITCH && n.(*ir.SwitchStmt).Tag != nil && n.(*ir.SwitchStmt).Tag.Op() == ir.OTYPESW && !n.(*ir.SwitchStmt).Tag.(*ir.TypeSwitchGuard).X.Type().IsEmptyInterface() {
for _, cc := range n.(*ir.SwitchStmt).Cases {
for _, c := range cc.List {
if c.Op() == ir.OTYPE && c.Type().HasTParam() {
// Type switch from a non-empty interface to a noninterface.
infoPrint(" Itab for type switch: %v\n", c)
info.itabConvs = append(info.itabConvs, c)
if info.type2switchType == nil {
info.type2switchType = map[ir.Node]*types.Type{}
}
info.type2switchType[c] = n.(*ir.SwitchStmt).Tag.(*ir.TypeSwitchGuard).X.Type()
}
}
}
}
addType(&info, n, n.Type())
}