pkg/compiler: fix crash on fmt[flags]

Flags with only 1 value 0 are transformed to ConstType.
Fmt did not expect that.

Fixes #1965

2 files changed, 9 insertions, 0 deletions

diff --git a/pkg/compiler/testdata/all.txt b/pkg/compiler/testdata/all.txt
index f5f3f1070..b9e144d73 100644
--- a/pkg/compiler/testdata/all.txt
+++ b/pkg/compiler/testdata/all.txt
@@ -294,7 +294,10 @@ foo_fmt2(a ptr[in, fmt[oct, len[b]]], b ptr[in, array[int8]])
 foo_fmt3(a ptr[in, fmt[dec, proc[10, 20]]])
 foo_fmt4(a ptr[in, fmt[dec, r0]])
 foo_fmt5(a ptr[in, struct$fmt0])
+foo_fmt6(a ptr[in, fmt[dec, flags[flags_with_one_value]]])
 
 struct$fmt0 {
 	f0	fmt[dec, int8]
 }
+
+flags_with_one_value = 0
diff --git a/pkg/compiler/types.go b/pkg/compiler/types.go
index 122c4a9d4..3c22038f8 100644
--- a/pkg/compiler/types.go
+++ b/pkg/compiler/types.go
@@ -761,6 +761,12 @@ var typeFmt = &typeDesc{
 			t.ArgFormat = format
 			t.TypeSize = size
 			t.TypeAlign = 1
+		case *prog.ConstType:
+			// We don't allow fmt[const] directly, but flags with only 1 value
+			// are transformed to ConstType.
+			t.ArgFormat = format
+			t.TypeSize = size
+			t.TypeAlign = 1
 		default:
 			panic(fmt.Sprintf("unexpected type: %#v", typ))
 		}