cmd/compile: fix irgen reports wrong error message for misuse of //go:embed

Fixes #48230

Change-Id: Ic6490e065e7e79793faa0d0201dc94f5fcea694a
Reviewed-on: https://go-review.googlesource.com/c/go/+/355529
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Dan Scales <danscales@google.com>

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

@@ -132,7 +132,11 @@ func (g *irgen) funcDecl(out *ir.Nodes, decl *syntax.FuncDecl) {
 		g.target.Inits = append(g.target.Inits, fn)
 	}
 
+	haveEmbed := g.haveEmbed
 	g.later(func() {
+		defer func(b bool) { g.haveEmbed = b }(g.haveEmbed)
+
+		g.haveEmbed = haveEmbed
 		if fn.Type().HasTParam() {
 			g.topFuncIsGeneric = true
 		}
@@ -241,12 +245,15 @@ func (g *irgen) varDecl(out *ir.Nodes, decl *syntax.VarDecl) {
 
 	if decl.Pragma != nil {
 		pragma := decl.Pragma.(*pragmas)
-		// TODO(mdempsky): Plumb noder.importedEmbed through to here.
-		varEmbed(g.makeXPos, names[0], decl, pragma, true)
+		varEmbed(g.makeXPos, names[0], decl, pragma, g.haveEmbed)
 		g.reportUnused(pragma)
 	}
 
+	haveEmbed := g.haveEmbed
 	do := func() {
+		defer func(b bool) { g.haveEmbed = b }(g.haveEmbed)
+
+		g.haveEmbed = haveEmbed
 		values := g.exprList(decl.Values)
 
 		var as2 *ir.AssignListStmt

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

@@ -147,6 +147,9 @@ type irgen struct {
 	// laterFuncs records tasks that need to run after all declarations
 	// are processed.
 	laterFuncs []func()
+	// haveEmbed indicates whether the current node belongs to file that
+	// imports "embed" package.
+	haveEmbed bool
 
 	// exprStmtOK indicates whether it's safe to generate expressions or
 	// statements yet.
@@ -254,8 +257,11 @@ Outer:
 	types.ResumeCheckSize()
 
 	// 3. Process all remaining declarations.
-	for _, declList := range declLists {
+	for i, declList := range declLists {
+		old := g.haveEmbed
+		g.haveEmbed = noders[i].importedEmbed
 		g.decls((*ir.Nodes)(&g.target.Decls), declList)
+		g.haveEmbed = old
 	}
 	g.exprStmtOK = true
 

src/cmd/compile/internal/types2/stdlib_test.go

@@ -193,7 +193,7 @@ func TestStdFixed(t *testing.T) {
 		"issue42058a.go", // types2 does not have constraints on channel element size
 		"issue42058b.go", // types2 does not have constraints on channel element size
 		"issue48097.go",  // go/types doesn't check validity of //go:xxx directives, and non-init bodyless function
-
+		"issue48230.go",  // go/types doesn't check validity of //go:xxx directives
 	)
 }
 

src/go/types/stdlib_test.go

@@ -195,6 +195,7 @@ func TestStdFixed(t *testing.T) {
 		"issue42058a.go", // go/types does not have constraints on channel element size
 		"issue42058b.go", // go/types does not have constraints on channel element size
 		"issue48097.go",  // go/types doesn't check validity of //go:xxx directives, and non-init bodyless function
+		"issue48230.go",  // go/types doesn't check validity of //go:xxx directives
 	)
 }
 

test/fixedbugs/issue48230.go

@@ -0,0 +1,10 @@
+// errorcheck
+
+// 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.
+
+package p
+
+//go:embed issue48230.go // ERROR `go:embed only allowed in Go files that import "embed"`
+var _ string