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cmd/compile: trim range typechecking 

Most of the code is not necessary anymore.
Before we start changing how range works,
delete this code so it won't need updating.

Preparation for proposal #61405.

Change-Id: Ia6c6cc62b156e38a871279350a2e60c189967cac
Reviewed-on: https://go-review.googlesource.com/c/go/+/510536
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This commit is contained in:
Russ Cox 2023-06-14 11:29:59 -04:00
parent 53895bf993
commit ade5a6232f
1 changed files with 16 additions and 75 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

91
src/cmd/compile/internal/typecheck/stmt.go
View File

@ -20,70 +20,6 @@ func RangeExprType(t *types.Type) *types.Type {
}
func typecheckrangeExpr(n *ir.RangeStmt) {
n.X = Expr(n.X)
if n.X.Type() == nil {
return
}
t := RangeExprType(n.X.Type())
// delicate little dance. see tcAssignList
if n.Key != nil && !ir.DeclaredBy(n.Key, n) {
n.Key = AssignExpr(n.Key)
}
if n.Value != nil && !ir.DeclaredBy(n.Value, n) {
n.Value = AssignExpr(n.Value)
}
var tk, tv *types.Type
toomany := false
switch t.Kind() {
default:
base.ErrorfAt(n.Pos(), errors.InvalidRangeExpr, "cannot range over %L", n.X)
return
case types.TARRAY, types.TSLICE:
tk = types.Types[types.TINT]
tv = t.Elem()
case types.TMAP:
tk = t.Key()
tv = t.Elem()
case types.TCHAN:
if !t.ChanDir().CanRecv() {
base.ErrorfAt(n.Pos(), errors.InvalidRangeExpr, "invalid operation: range %v (receive from send-only type %v)", n.X, n.X.Type())
return
}
tk = t.Elem()
tv = nil
if n.Value != nil {
toomany = true
}
case types.TSTRING:
tk = types.Types[types.TINT]
tv = types.RuneType
}
if toomany {
base.ErrorfAt(n.Pos(), errors.InvalidIterVar, "too many variables in range")
}
do := func(nn ir.Node, t *types.Type) {
if nn != nil {
if ir.DeclaredBy(nn, n) && nn.Type() == nil {
nn.SetType(t)
} else if nn.Type() != nil {
if op, why := Assignop(t, nn.Type()); op == ir.OXXX {
base.ErrorfAt(n.Pos(), errors.InvalidIterVar, "cannot assign type %v to %L in range%s", t, nn, why)
}
}
checkassign(nn)
}
}
do(n.Key, tk)
do(n.Value, tv)
}
// type check assignment.
@ -335,18 +271,23 @@ func tcIf(n *ir.IfStmt) ir.Node {
// range
func tcRange(n *ir.RangeStmt) {
// Typechecking order is important here:
// 0. first typecheck range expression (slice/map/chan),
// it is evaluated only once and so logically it is not part of the loop.
// 1. typecheck produced values,
// this part can declare new vars and so it must be typechecked before body,
// because body can contain a closure that captures the vars.
// 2. decldepth++ to denote loop body.
// 3. typecheck body.
// 4. decldepth--.
typecheckrangeExpr(n)
n.X = Expr(n.X)
// second half of dance, the first half being typecheckrangeExpr
// delicate little dance. see tcAssignList
if n.Key != nil {
if !ir.DeclaredBy(n.Key, n) {
n.Key = AssignExpr(n.Key)
}
checkassign(n.Key)
}
if n.Value != nil {
if !ir.DeclaredBy(n.Value, n) {
n.Value = AssignExpr(n.Value)
}
checkassign(n.Value)
}
// second half of dance
n.SetTypecheck(1)
if n.Key != nil && n.Key.Typecheck() == 0 {
n.Key = AssignExpr(n.Key)