pkg/compiler: support complex len targets

This change adds compiler support for complex path
expressions in len targets. E.g. it allows to refer
to a sibling field as len[parent_struct:field:another_field].
See the docs change for details.

This is just a compiler change.
The feature is not yet supported by the prog package.

3 files changed, 62 insertions, 4 deletions

diff --git a/pkg/compiler/testdata/all.txt b/pkg/compiler/testdata/all.txt
index 49cc1ffb9..7acb47743 100644
--- a/pkg/compiler/testdata/all.txt
+++ b/pkg/compiler/testdata/all.txt
@@ -70,6 +70,33 @@ foo$len_templ(a ptr[in, len_templ1[int8, int16]])
 foo$len_var0(a ptr[in, array[string]], b len[a])
 foo$len_var1(a ptr[in, array[string]], b ptr[in, len[a, int32]])
 
+len_expr1 {
+	f11	len_expr2
+}
+
+len_expr2 {
+	f21	len_expr3
+	f22	len_expr4
+	f23	ptr[in, len_expr4]
+	f24	ptr[in, ptr[in, len_expr4]]
+	f25	len[f21:f31, int32]
+}
+
+len_expr3 {
+	f31	int32
+	f32	bytesize[len_expr2:f21, int32]
+	f33	bytesize[len_expr2:f22:f41, int32]
+	f34	bytesize[len_expr1:f11:f22:f41, int32]
+	f35	bytesize[len_expr2:f23:f41, int32]
+	f36	bytesize[len_expr2:f24:f41, int32]
+}
+
+len_expr4 {
+	f41	int32
+}
+
+foo$len_expr(a ptr[in, len_expr1])
+
 # Pointer type.
 
 foo$ptr(a ptr[in, int64])
diff --git a/pkg/compiler/testdata/errors.txt b/pkg/compiler/testdata/errors.txt
index e95c3be7d..8c44694bb 100644
--- a/pkg/compiler/testdata/errors.txt
+++ b/pkg/compiler/testdata/errors.txt
@@ -62,7 +62,7 @@ sf2 = "a", "b"
 sf2 = "c"			### string flags sf2 redeclared, previously declared at LOCATION
 
 resource r2[r0]: 2
-resource r3[int32:1]		###  unexpected ':', only struct fields can be bitfields
+resource r3[int32:1]		### unexpected ':', only struct fields can be bitfields
 resource r4[int32[opt]]		### resource base can't be marked as opt
 resource r5[non_existent]	### unknown type non_existent
 resource r6[int64be]		### int64be can't be resource base (int types can)
@@ -119,6 +119,9 @@ foo$61(a u6)			### u6 can't be syscall argument
 foo$62() u6			### u6 can't be syscall return
 foo$63(a int32[1[2]])		### range argument has subargs
 foo$64(a ptr[in, flags[f1[int32], int32]])	### flags argument has subargs
+foo$65(a int32, b len[1])	### unexpected int 1 for len target argument of len type, expect identifier
+foo$66(a int32, b len[a:1])	### unexpected int 1 after colon, expect identifier
+foo$67(x int32[1:2:3, opt])	### unexpected ':'
 
 opt {				### struct uses reserved name opt
 	f1	int32
diff --git a/pkg/compiler/testdata/errors2.txt b/pkg/compiler/testdata/errors2.txt
index 77db29197..6b7737ef5 100644
--- a/pkg/compiler/testdata/errors2.txt
+++ b/pkg/compiler/testdata/errors2.txt
@@ -80,8 +80,8 @@ foo$sr0(a ptr[in, use_sr])
 # Len target tests.
 
 foo$100(a int32, b len[a])
-foo$101(a len[a])		### len target a refer to itself
-foo$102(a ptr[in, len[a, int8]])	### len target a refer to itself
+foo$101(a len[a])		### len target a refers to itself
+foo$102(a ptr[in, len[a, int8]])	### len target a refers to itself
 foo$103(a int32, b len[c])	### len target c does not exist
 foo$104(a len[parent])		### len target parent does not exist
 foo$105(a ptr[in, int32], b ptr[in, array[len[a, int32]]])
@@ -109,6 +109,15 @@ s6 {
 	f2	array[int8]
 } [size[10]]			### varlen struct s6 has size attribute
 
+s7 {
+	f1	int32
+	f2	u0
+}
+
+u0 [
+	f	len[f1, int32]	### len target f1 does not exist
+]
+
 u1 [
 	f1	ptr[in, array[int8]]
 	f2	len[f1, int32]	### len target f1 does not exist
@@ -124,7 +133,26 @@ u3 [
 
 foo$200(a ptr[in, s2])
 foo$201(a ptr[in, s1])
-foo$202(a u1)
+foo$202(a ptr[in, s7])
+foo$203(a u1)
+
+foo$204(a ptr[in, slen1])
+
+slen1 {
+	f0 len[parent, int32]
+	f1 len[parent:f0, int32]	### parent can't be part of path expressions
+	f2 len[slen21:a, int32]		### len target a does not exist
+	f3 len[f0:parent, int32]	### parent can't be part of path expressions
+	f4 len[slen2:f, int32]		### len path slen2 does not refer to a struct
+	f5 len[slen22:f, int32]		### len path slen22 does not refer to a struct
+	slen2 ptr[in, array[slen2]]
+	slen21 slen2
+	slen22 array[slen2]
+}
+
+slen2 {
+	f int32
+}
 
 # Resource ctor tests.