[dev.typeparams] cmd/compile: fix unified IR support for //go:nointerface

This CL changes fixedbugs/issue30862.go into a "runindir" test so that
it can use '-goexperiment fieldtrack' and test that //go:nointerface
works with cmd/compile. In particular, this revealed that -G=3 and
unified IR did not handle it correctly.

This CL also fixes unified IR's support for //go:nointerface and adds
a test that checks that //go:nointerface, promoted methods, and
generics all interact as expected.

Updates #47045.

Change-Id: Ib8acff8ae18bf124520d00c98e8915699cba2abd
Reviewed-on: https://go-review.googlesource.com/c/go/+/332611
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>

src/cmd/compile/internal/noder/reader.go

@@ -750,13 +750,12 @@ func (r *reader) method() *types.Field {
 	name.Func = ir.NewFunc(r.pos())
 	name.Func.Nname = name
 
-	// TODO(mdempsky): Make sure we're handling //go:nointerface
-	// correctly. I don't think this is exercised within the Go repo.
-
 	r.ext.funcExt(name)
 
 	meth := types.NewField(name.Func.Pos(), sym, typ)
 	meth.Nname = name
+	meth.SetNointerface(name.Func.Pragma&ir.Nointerface != 0)
+
 	return meth
 }
 

test/fixedbugs/issue30862.dir/b/b.go

@@ -4,7 +4,7 @@
 
 package b
 
-import "./a"
+import "issue30862.dir/a"
 
 type EmbedImported struct {
 	a.NoitfStruct

test/fixedbugs/issue30862.dir/main.go

@@ -8,7 +8,7 @@ import (
 	"fmt"
 	"os"
 
-	"./b"
+	"issue30862.dir/b"
 )
 
 // Test case for issue 30862.

test/fixedbugs/issue30862.go

@@ -1,4 +1,4 @@
-// rundir
+// runindir -goexperiment fieldtrack
 
 // Copyright 2019 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -9,6 +9,4 @@
 // is set when building it, whereas gccgo has field tracking
 // enabled by default (hence the build tag below).
 
-// +build gccgo
-
 package ignored

test/run.go

@@ -2180,12 +2180,14 @@ var types2Failures32Bit = setOf(
 var g3Failures = setOf(
 	"writebarrier.go", // correct diagnostics, but different lines (probably irgen's fault)
 
+	"fixedbugs/issue30862.go", // -G=3 doesn't handle //go:nointerface
+
+	"typeparam/cons.go",   // causes an unreachable method
 	"typeparam/nested.go", // -G=3 doesn't support function-local types with generics
 
 	"typeparam/mdempsky/4.go",  // -G=3 can't export functions with labeled breaks in loops
 	"typeparam/mdempsky/13.go", // problem with interface as as a type arg.
-
-	"typeparam/cons.go", // causes an unreachable method
+	"typeparam/mdempsky/15.go", // ICE in (*irgen).buildClosure
 )
 
 var unifiedFailures = setOf(

test/typeparam/mdempsky/15.go

@@ -0,0 +1,69 @@
+// run -goexperiment fieldtrack -gcflags=-G=3
+
+// 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.
+
+// Test that generics, promoted methods, and //go:nointerface
+// interoperate as expected.
+
+package main
+
+import (
+	"reflect"
+)
+
+func TypeString[T any]() string {
+	return reflect.TypeOf(new(T)).Elem().String()
+}
+
+func Test[T, Bad, Good any]() {
+	switch interface{}(new(T)).(type) {
+	case Bad:
+		println("FAIL:", TypeString[T](), "matched", TypeString[Bad]())
+	case Good:
+		// ok
+	default:
+		println("FAIL:", TypeString[T](), "did not match", TypeString[Good]())
+	}
+}
+
+func TestE[T any]() { Test[T, interface{ EBad() }, interface{ EGood() }]() }
+func TestX[T any]() { Test[T, interface{ XBad() }, interface{ XGood() }]() }
+
+type E struct{}
+
+//go:nointerface
+func (E) EBad()  {}
+func (E) EGood() {}
+
+type X[T any] struct{ E }
+
+//go:nointerface
+func (X[T]) XBad()  {}
+func (X[T]) XGood() {}
+
+type W struct{ X[int] }
+
+func main() {
+	_ = E.EGood
+	_ = E.EBad
+
+	TestE[E]()
+
+	_ = X[int].EGood
+	_ = X[int].EBad
+	_ = X[int].XGood
+	_ = X[int].XBad
+
+	TestE[X[int]]()
+	TestX[X[int]]()
+
+	_ = W.EGood
+	_ = W.EBad
+	_ = W.XGood
+	_ = W.XBad
+
+	TestE[W]()
+	TestX[W]()
+}