pkg/compiler: check for flags with all equal values

There is no point in having flags when values are equal.
This can only mean a typo or other bug. Check for such cases
and fix 3 existing precedents.

2 files changed, 17 insertions, 1 deletions

diff --git a/pkg/compiler/check.go b/pkg/compiler/check.go
index 468b6e35e..022581771 100644
--- a/pkg/compiler/check.go
+++ b/pkg/compiler/check.go
@@ -248,7 +248,7 @@ func (comp *compiler) checkTypes() {
 
 func (comp *compiler) checkTypeValues() {
 	for _, decl := range comp.desc.Nodes {
-		switch decl.(type) {
+		switch n := decl.(type) {
 		case *ast.Call, *ast.Struct, *ast.Resource, *ast.TypeDef:
 			comp.foreachType(decl, func(t *ast.Type, desc *typeDesc,
 				args []*ast.Type, base prog.IntTypeCommon) {
@@ -261,6 +261,16 @@ func (comp *compiler) checkTypeValues() {
 					}
 				}
 			})
+		case *ast.IntFlags:
+			allEqual := len(n.Values) >= 2
+			for _, val := range n.Values {
+				if val.Value != n.Values[0].Value {
+					allEqual = false
+				}
+			}
+			if allEqual {
+				comp.error(n.Pos, "all %v values are equal %v", n.Name.Name, n.Values[0].Value)
+			}
 		}
 	}
 }
diff --git a/pkg/compiler/testdata/errors2.txt b/pkg/compiler/testdata/errors2.txt
index c862358cf..111db587f 100644
--- a/pkg/compiler/testdata/errors2.txt
+++ b/pkg/compiler/testdata/errors2.txt
@@ -370,6 +370,12 @@ foo$534(a ptr[in, flags[large_flags, int8]])	### large_flags U16_MAX=0xffff does
 
 large_flags = U8_MAX, U16_MAX
 
+equal_flags_0 = 0, 0, 0, 0		### all equal_flags_0 values are equal 0
+equal_flags_1 = 42, 42, 42, 42		### all equal_flags_1 values are equal 42
+non_equal_flags = 0, 0, 0, 1
+
+equal_flags_call(a flags[equal_flags_0], b flags[equal_flags_1], c flags[non_equal_flags])
+
 type type500 proc[C1, 8, int8]	### values starting from 1 with step 8 overflow base type for 32 procs
 type type501 int8		### unused type type501
 type type502[C] const[C, int8]	### unused type type502