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>

4 files changed, 124 insertions, 7 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]
diff --git a/test/closure3.dir/main.go b/test/closure3.dir/main.go
index 2fc33753ed..662a2e967b 100644
--- a/test/closure3.dir/main.go
+++ b/test/closure3.dir/main.go
@@ -94,10 +94,10 @@ func main() {
 			return x + 2
 		}
 		y, sink = func() (func(int) int, int) { // ERROR "can inline main.func12"
-			return func(x int) int { // ERROR "can inline main.func12"
+			return func(x int) int { // ERROR "func literal does not escape" "can inline main.func12"
 				return x + 1
 			}, 42
-		}() // ERROR "func literal does not escape" "inlining call to main.func12"
+		}() // ERROR "inlining call to main.func12"
 		if y(40) != 41 {
 			ppanic("y(40) != 41")
 		}
@@ -109,10 +109,10 @@ func main() {
 				return x + 2
 			}
 			y, sink = func() (func(int) int, int) { // ERROR "can inline main.func13.2"
-				return func(x int) int { // ERROR "can inline main.func13.2"
+				return func(x int) int { // ERROR  "func literal does not escape" "can inline main.func13.2"
 					return x + 1
 				}, 42
-			}() // ERROR "inlining call to main.func13.2" "func literal does not escape"
+			}() // ERROR "inlining call to main.func13.2"
 			if y(40) != 41 {
 				ppanic("y(40) != 41")
 			}
diff --git a/test/fixedbugs/issue46234.go b/test/fixedbugs/issue46234.go
new file mode 100644
index 0000000000..c669cc01a6
--- /dev/null
+++ b/test/fixedbugs/issue46234.go
@@ -0,0 +1,103 @@
+// buildrun -t 30
+
+// +build !js
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Ensure that runtime traceback does not infinite loop for
+// the testcase below.
+
+package main
+
+import (
+	"bytes"
+	"io/ioutil"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+)
+
+const prog = `
+
+package main
+
+import "context"
+
+var gpi *int
+
+type nAO struct {
+	eE bool
+}
+
+type NAO func(*nAO)
+
+func WEA() NAO {
+	return func(o *nAO) { o.eE = true }
+}
+
+type R struct {
+	cM *CM
+}
+
+type CM int
+
+type A string
+
+func (m *CM) NewA(ctx context.Context, cN string, nn *nAO, opts ...NAO) (*A, error) {
+	for _, o := range opts {
+		o(nn)
+	}
+	s := A("foo")
+	return &s, nil
+}
+
+func (r *R) CA(ctx context.Context, cN string, nn *nAO) (*int, error) {
+	cA, err := r.cM.NewA(ctx, cN, nn, WEA(), WEA())
+	if err == nil {
+		return nil, err
+	}
+	println(cA)
+	x := int(42)
+	return &x, nil
+}
+
+func main() {
+	c := CM(1)
+	r := R{cM: &c}
+	var ctx context.Context
+	nnr := nAO{}
+	pi, err := r.CA(ctx, "foo", nil)
+	if err != nil {
+		panic("bad")
+	}
+	println(nnr.eE)
+	gpi = pi
+}
+`
+
+func main() {
+	dir, err := ioutil.TempDir("", "46234")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer os.RemoveAll(dir)
+
+	file := filepath.Join(dir, "main.go")
+	if err := ioutil.WriteFile(file, []byte(prog), 0655); err != nil {
+		log.Fatalf("Write error %v", err)
+	}
+
+	cmd := exec.Command("go", "run", file)
+	output, err := cmd.CombinedOutput()
+	if err == nil {
+		log.Fatalf("Passed, expected an error")
+	}
+
+	want := []byte("segmentation violation")
+	if !bytes.Contains(output, want) {
+		log.Fatalf("Unmatched error message %q:\nin\n%s\nError: %v", want, output, err)
+	}
+}
diff --git a/test/inline.go b/test/inline.go
index bc23768d01..472a941dca 100644
--- a/test/inline.go
+++ b/test/inline.go
@@ -92,9 +92,9 @@ func o() int {
 	foo := func() int { return 1 } // ERROR "can inline o.func1" "func literal does not escape"
 	func(x int) {                  // ERROR "can inline o.func2"
 		if x > 10 {
-			foo = func() int { return 2 } // ERROR "can inline o.func2"
+			foo = func() int { return 2 } // ERROR "func literal does not escape" "can inline o.func2"
 		}
-	}(11) // ERROR "func literal does not escape" "inlining call to o.func2"
+	}(11) // ERROR "inlining call to o.func2"
 	return foo()
 }