cmd/compile: be sure to export types mentioned in f.i.g. method signature

When a fully instantiated generic method is exported, be sure to also
export the types in its signature.

Fixes #52279.

Change-Id: Icc6bca05b01f914cf67faaf1bf184eaa5484f521
Reviewed-on: https://go-review.googlesource.com/c/go/+/405118
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

4 files changed, 38 insertions, 1 deletions

diff --git a/src/cmd/compile/internal/typecheck/crawler.go b/src/cmd/compile/internal/typecheck/crawler.go
index 40b518983a..f14d885564 100644
--- a/src/cmd/compile/internal/typecheck/crawler.go
+++ b/src/cmd/compile/internal/typecheck/crawler.go
@@ -234,7 +234,7 @@ func (p *crawler) checkForFullyInst(t *types.Type) {
 		for i, t1 := range t.RParams() {
 			shapes[i] = Shapify(t1, i, baseType.RParams()[i])
 		}
-		for j := range t.Methods().Slice() {
+		for j, tmethod := range t.Methods().Slice() {
 			baseNname := baseType.Methods().Slice()[j].Nname.(*ir.Name)
 			dictsym := MakeDictSym(baseNname.Sym(), t.RParams(), true)
 			if dictsym.Def == nil {
@@ -255,6 +255,8 @@ func (p *crawler) checkForFullyInst(t *types.Type) {
 				ImportedBody(methNode.Func)
 				methNode.Func.SetExportInline(true)
 			}
+			// Make sure that any associated types are also exported. (See #52279)
+			p.checkForFullyInst(tmethod.Type)
 		}
 	}
 
diff --git a/test/fixedbugs/issue52279.dir/lib.go b/test/fixedbugs/issue52279.dir/lib.go
new file mode 100644
index 0000000000..e20de30bd5
--- /dev/null
+++ b/test/fixedbugs/issue52279.dir/lib.go
@@ -0,0 +1,23 @@
+package lib
+
+type FMap[K comparable, V comparable] map[K]V
+
+//go:noinline
+func (m FMap[K, V]) Flip() FMap[V, K] {
+	out := make(FMap[V, K])
+	return out
+}
+
+type MyType uint8
+
+const (
+	FIRST MyType = 0
+)
+
+var typeStrs = FMap[MyType, string]{
+	FIRST: "FIRST",
+}
+
+func (self MyType) String() string {
+	return typeStrs[self]
+}
diff --git a/test/fixedbugs/issue52279.dir/main.go b/test/fixedbugs/issue52279.dir/main.go
new file mode 100644
index 0000000000..8c7e069c5b
--- /dev/null
+++ b/test/fixedbugs/issue52279.dir/main.go
@@ -0,0 +1,5 @@
+package main
+
+import "./lib"
+
+func main() { lib.FIRST.String() }
diff --git a/test/fixedbugs/issue52279.go b/test/fixedbugs/issue52279.go
new file mode 100644
index 0000000000..aefbe67310
--- /dev/null
+++ b/test/fixedbugs/issue52279.go
@@ -0,0 +1,7 @@
+// rundir
+
+// Copyright 2022 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.
+
+package ignored