pkg/compiler: fix potential nil deref

One one found on fuzzbuzz.io.
google · Mar 6, 2019 · 967dc02 · 967dc02
1 parent 05cf83b
commit 967dc02
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Showing 2 changed files with 4 additions and 1 deletion.
diff --git a/pkg/compiler/check.go b/pkg/compiler/check.go
@@ -870,8 +870,9 @@ func (comp *compiler) replaceTypedef(ctx *checkCtx, t *ast.Type, flags checkFlag
 	t.Pos = pos0
 
 	// Remove base type if it's not needed in this context.
+	// If desc is nil, will return an error later when we typecheck the result.
 	desc := comp.getTypeDesc(t)
-	if flags&checkIsArg != 0 && desc.NeedBase {
+	if desc != nil && flags&checkIsArg != 0 && desc.NeedBase {
 		baseTypePos := len(t.Args) - 1
 		if t.Args[baseTypePos].Ident == "opt" {
 			baseTypePos--

diff --git a/pkg/compiler/compiler_test.go b/pkg/compiler/compiler_test.go
@@ -197,6 +197,8 @@ func TestFuzz(t *testing.T) {
 		`t[
 l	t
 ]`,
+		`t()D[0]
+type D[e]l`,
 	}
 	consts := map[string]uint64{"A": 1, "B": 2, "C": 3, "SYS_A": 4, "SYS_B": 5, "SYS_C": 6}
 	eh := func(pos ast.Pos, msg string) {