cmd/compile: don't emit inltree for closure within body of inlined func

When inlining functions with closures, ensure that we don't mark the
body of the closure with a src.Pos marker that reflects the inline,
since this will result in the generation of an inltree table for the
closure itself (as opposed to the routine that the func-with-closure
was inlined into).

Fixes #46234.

Change-Id: I348296de6504fc4745d99adab436640f50be299a
Reviewed-on: https://go-review.googlesource.com/c/go/+/320913
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Than McIntosh <thanm@google.com>

1 files changed, 15 insertions, 1 deletions

diff --git a/src/cmd/compile/internal/inline/inl.go b/src/cmd/compile/internal/inline/inl.go
index a6829e9835..d6b4ced4e1 100644
--- a/src/cmd/compile/internal/inline/inl.go
+++ b/src/cmd/compile/internal/inline/inl.go
@@ -1124,6 +1124,10 @@ type inlsubst struct {
 	newclofn *ir.Func
 
 	fn *ir.Func // For debug -- the func that is being inlined
+
+	// If true, then don't update source positions during substitution
+	// (retain old source positions).
+	noPosUpdate bool
 }
 
 // list inlines a list of nodes.
@@ -1219,7 +1223,14 @@ func (subst *inlsubst) clovar(n *ir.Name) *ir.Name {
 // closure node.
 func (subst *inlsubst) closure(n *ir.ClosureExpr) ir.Node {
 	m := ir.Copy(n)
-	m.SetPos(subst.updatedPos(m.Pos()))
+
+	// Prior to the subst edit, set a flag in the inlsubst to
+	// indicated that we don't want to update the source positions in
+	// the new closure. If we do this, it will appear that the closure
+	// itself has things inlined into it, which is not the case. See
+	// issue #46234 for more details.
+	defer func(prev bool) { subst.noPosUpdate = prev }(subst.noPosUpdate)
+	subst.noPosUpdate = true
 	ir.EditChildren(m, subst.edit)
 
 	//fmt.Printf("Inlining func %v with closure into %v\n", subst.fn, ir.FuncName(ir.CurFunc))
@@ -1445,6 +1456,9 @@ func (subst *inlsubst) node(n ir.Node) ir.Node {
 }
 
 func (subst *inlsubst) updatedPos(xpos src.XPos) src.XPos {
+	if subst.noPosUpdate {
+		return xpos
+	}
 	pos := base.Ctxt.PosTable.Pos(xpos)
 	oldbase := pos.Base() // can be nil
 	newbase := subst.bases[oldbase]