[dev.regabi] cmd/compile: remove CommStmt.List

Package syntax's parser already ensures that select communication
clauses only have one statement, so there's no need for ir's CommStmt
to need to represent more than one. Instead, noder can just directly
populate Comm in the first place.

Incidentally, this also revealed a latent issue in the inline-body
exporter: we were exporting List (where the case statement is before
type-checking), rather than Comm (where the case statement would be
after type-checking, when export happens).

Passes toolstash -cmp.

Change-Id: Ib4eb711527bed297c7332c79ed6e6562a1db2cfa
Reviewed-on: https://go-review.googlesource.com/c/go/+/280444
Trust: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>

1 files changed, 10 insertions, 13 deletions

diff --git a/src/cmd/compile/internal/noder/noder.go b/src/cmd/compile/internal/noder/noder.go
index ff699cd54d..19a88e21a2 100644
--- a/src/cmd/compile/internal/noder/noder.go
+++ b/src/cmd/compile/internal/noder/noder.go
@@ -1149,9 +1149,11 @@ func (p *noder) blockStmt(stmt *syntax.BlockStmt) []ir.Node {
 
 func (p *noder) ifStmt(stmt *syntax.IfStmt) ir.Node {
 	p.openScope(stmt.Pos())
-	init := p.simpleStmt(stmt.Init)
+	init := p.stmt(stmt.Init)
 	n := ir.NewIfStmt(p.pos(stmt), p.expr(stmt.Cond), p.blockStmt(stmt.Then), nil)
-	*n.PtrInit() = init
+	if init != nil {
+		*n.PtrInit() = []ir.Node{init}
+	}
 	if stmt.Else != nil {
 		e := p.stmt(stmt.Else)
 		if e.Op() == ir.OBLOCK {
@@ -1186,7 +1188,7 @@ func (p *noder) forStmt(stmt *syntax.ForStmt) ir.Node {
 		return n
 	}
 
-	n := ir.NewForStmt(p.pos(stmt), p.simpleStmt(stmt.Init), p.expr(stmt.Cond), p.stmt(stmt.Post), p.blockStmt(stmt.Body))
+	n := ir.NewForStmt(p.pos(stmt), p.stmt(stmt.Init), p.expr(stmt.Cond), p.stmt(stmt.Post), p.blockStmt(stmt.Body))
 	p.closeAnotherScope()
 	return n
 }
@@ -1194,9 +1196,11 @@ func (p *noder) forStmt(stmt *syntax.ForStmt) ir.Node {
 func (p *noder) switchStmt(stmt *syntax.SwitchStmt) ir.Node {
 	p.openScope(stmt.Pos())
 
-	init := p.simpleStmt(stmt.Init)
+	init := p.stmt(stmt.Init)
 	n := ir.NewSwitchStmt(p.pos(stmt), p.expr(stmt.Tag), nil)
-	*n.PtrInit() = init
+	if init != nil {
+		*n.PtrInit() = []ir.Node{init}
+	}
 
 	var tswitch *ir.TypeSwitchGuard
 	if l := n.Tag; l != nil && l.Op() == ir.OTYPESW {
@@ -1259,13 +1263,6 @@ func (p *noder) selectStmt(stmt *syntax.SelectStmt) ir.Node {
 	return ir.NewSelectStmt(p.pos(stmt), p.commClauses(stmt.Body, stmt.Rbrace))
 }
 
-func (p *noder) simpleStmt(stmt syntax.SimpleStmt) []ir.Node {
-	if stmt == nil {
-		return nil
-	}
-	return []ir.Node{p.stmt(stmt)}
-}
-
 func (p *noder) commClauses(clauses []*syntax.CommClause, rbrace syntax.Pos) []*ir.CommStmt {
 	nodes := make([]*ir.CommStmt, len(clauses))
 	for i, clause := range clauses {
@@ -1275,7 +1272,7 @@ func (p *noder) commClauses(clauses []*syntax.CommClause, rbrace syntax.Pos) []*
 		}
 		p.openScope(clause.Pos())
 
-		nodes[i] = ir.NewCommStmt(p.pos(clause), p.simpleStmt(clause.Comm), p.stmts(clause.Body))
+		nodes[i] = ir.NewCommStmt(p.pos(clause), p.stmt(clause.Comm), p.stmts(clause.Body))
 	}
 	if len(clauses) > 0 {
 		p.closeScope(rbrace)