pkg/compiler: prohibit use of direction attribute on union fields

Direction attributes on unions work in a confusing way and don't do
what users may think they do. Now we have out_overlay attribute
for structs that allows to have overlapping input and output fields.

5 files changed, 19 insertions, 20 deletions

diff --git a/pkg/compiler/attrs.go b/pkg/compiler/attrs.go
index 63ba613d9..46ba89b23 100644
--- a/pkg/compiler/attrs.go
+++ b/pkg/compiler/attrs.go
@@ -28,10 +28,10 @@ var (
 	attrInOut      = &attrDesc{Name: "inout"}
 	attrOutOverlay = &attrDesc{Name: "out_overlay"}
 
-	structAttrs = makeAttrs(attrPacked, attrSize, attrAlign)
-	unionAttrs  = makeAttrs(attrVarlen, attrSize)
-	fieldAttrs  = makeAttrs(attrIn, attrOut, attrInOut, attrOutOverlay)
-	callAttrs   = make(map[string]*attrDesc)
+	structAttrs      = makeAttrs(attrPacked, attrSize, attrAlign)
+	unionAttrs       = makeAttrs(attrVarlen, attrSize)
+	structFieldAttrs = makeAttrs(attrIn, attrOut, attrInOut, attrOutOverlay)
+	callAttrs        = make(map[string]*attrDesc)
 )
 
 func init() {
diff --git a/pkg/compiler/check.go b/pkg/compiler/check.go
index 676b96c5c..9f74f8a4b 100644
--- a/pkg/compiler/check.go
+++ b/pkg/compiler/check.go
@@ -184,7 +184,11 @@ func (comp *compiler) checkStructFields(n *ast.Struct, typ, name string) {
 	}
 	hasDirections, hasOutOverlay := false, false
 	for fieldIdx, f := range n.Fields {
-		attrs := comp.parseAttrs(fieldAttrs, f, f.Attrs)
+		if n.IsUnion {
+			comp.parseAttrs(nil, f, f.Attrs)
+			continue
+		}
+		attrs := comp.parseAttrs(structFieldAttrs, f, f.Attrs)
 		dirCount := attrs[attrIn] + attrs[attrOut] + attrs[attrInOut]
 		if dirCount != 0 {
 			hasDirections = true
@@ -194,10 +198,6 @@ func (comp *compiler) checkStructFields(n *ast.Struct, typ, name string) {
 			comp.error(f.Pos, "%v has multiple direction attributes", typ)
 		}
 		if attrs[attrOutOverlay] > 0 {
-			if n.IsUnion {
-				_, typ, name := f.Info()
-				comp.error(f.Pos, "unknown %v %v attribute %v", typ, name, attrOutOverlay.Name)
-			}
 			if fieldIdx == 0 {
 				comp.error(f.Pos, "%v attribute must not be specified on the first field", attrOutOverlay.Name)
 			}
@@ -325,7 +325,7 @@ func (comp *compiler) checkAttributeValues() {
 			for _, f := range st.Fields {
 				isOut := hasOutOverlay
 				for _, attr := range f.Attrs {
-					desc := fieldAttrs[attr.Ident]
+					desc := structFieldAttrs[attr.Ident]
 					if desc.CheckConsts != nil {
 						desc.CheckConsts(comp, f, attr)
 					}
diff --git a/pkg/compiler/gen.go b/pkg/compiler/gen.go
index 78cbc54fe..89571c966 100644
--- a/pkg/compiler/gen.go
+++ b/pkg/compiler/gen.go
@@ -456,7 +456,7 @@ func genPad(size uint64) prog.Field {
 func (comp *compiler) genFieldArray(fields []*ast.Field, argSizes []uint64) ([]prog.Field, int) {
 	outOverlay := -1
 	for i, f := range fields {
-		attrs := comp.parseAttrs(fieldAttrs, f, f.Attrs)
+		attrs := comp.parseAttrs(structFieldAttrs, f, f.Attrs)
 		if attrs[attrOutOverlay] > 0 {
 			outOverlay = i
 		}
@@ -476,7 +476,7 @@ func (comp *compiler) genFieldArray(fields []*ast.Field, argSizes []uint64) ([]p
 }
 
 func (comp *compiler) genFieldDir(f *ast.Field) (prog.Dir, bool) {
-	attrs := comp.parseAttrs(fieldAttrs, f, f.Attrs)
+	attrs := comp.parseAttrs(structFieldAttrs, f, f.Attrs)
 	switch {
 	case attrs[attrIn] != 0:
 		return prog.DirIn, true
diff --git a/pkg/compiler/testdata/errors.txt b/pkg/compiler/testdata/errors.txt
index 6cc2e2b0f..6d258cf50 100644
--- a/pkg/compiler/testdata/errors.txt
+++ b/pkg/compiler/testdata/errors.txt
@@ -412,3 +412,8 @@ union$overlay0 [
 	f0	int32
 	f1	int32	(out_overlay)	### unknown arg/field f1 attribute out_overlay
 ]
+
+union$directions [
+	f1	int32	(in)	### unknown arg/field f1 attribute in
+	f2	int32	(out)	### unknown arg/field f2 attribute out
+]
diff --git a/pkg/compiler/testdata/errors2.txt b/pkg/compiler/testdata/errors2.txt
index e5a51b4a9..c07e6a8a1 100644
--- a/pkg/compiler/testdata/errors2.txt
+++ b/pkg/compiler/testdata/errors2.txt
@@ -189,13 +189,12 @@ resource r117[int8]		### resource r117 is never used as an input(such resources
 resource r118[int8]		### resource r118 is never used as an input(such resources are not useful)
 resource r119[int8]		### resource r119 is never used as an input(such resources are not useful)
 resource r120[int8]		### resource r120 can't be created (never mentioned as a syscall return value or output argument/field)
-resource r121[int8]
 
 foo$300(a0 r100, a1 r101, a2 r102, a3 r103, a4 r104, a5 r105, a6 r106, a7 r107, a8 r108)
-foo$301(a0 r109, a1 r110, a2 r111, a3 r112, a4 r113, a5 r114, a6 r115, a7 r120, a8 r121)
+foo$301(a0 r109, a1 r110, a2 r111, a3 r112, a4 r113, a5 r114, a6 r115, a7 r120)
 foo$302(a ptr[out, array[r103]], b ptr[in, s300], c r107) r104
 foo$303(a ptr[in, s302], b ptr[in, s303], c ptr[in, s304], d ptr[out, s305], e ptr[inout, s306], f ptr[inout, s307], g ptr[in, s308], h ptr[out, s310])
-foo$304(a ptr[out, r117], b ptr[in, s312], c ptr[in, s313], d ptr[inout, u100]) r116
+foo$304(a ptr[out, r117], b ptr[in, s312], c ptr[in, s313]) r116
 
 s300 {
 	f1	ptr[inout, s301]
@@ -267,11 +266,6 @@ s314 {
 	f1	r119	(out)
 }
 
-u100 [
-	f1	r120	(in)
-	f2	r121	(out)
-]
-
 # TODO: Two instances of the same resource might exist in the same structure as
 # both in and out. How common is this and how to handle this?