sys: support type aliases (aka typedefs)

Complex types that are often repeated can be given short type aliases using the
following syntax:

```
type identifier underlying_type
```

For example:

```
type signalno int32[0:65]
type net_port proc[20000, 4, int16be]
```

Then, type alias can be used instead of the underlying type in any contexts.
Underlying type needs to be described as if it's a struct field, that is,
with the base type if it's required. However, type alias can be used as syscall
arguments as well. Underlying types are currently restricted to integer types,
`ptr`, `ptr64`, `const`, `flags` and `proc` types.

1 files changed, 63 insertions, 0 deletions

diff --git a/pkg/compiler/testdata/errors.txt b/pkg/compiler/testdata/errors.txt
index ade8c624f..237519aa3 100644
--- a/pkg/compiler/testdata/errors.txt
+++ b/pkg/compiler/testdata/errors.txt
@@ -178,3 +178,66 @@ define d1 `some C expression`
 define d2 some C expression
 define d2 SOMETHING		### duplicate define d2
 define d3 1
+
+# Type aliases.
+
+type bool8 int8[0:1]
+type bool16 int16[0:1]
+type net_port proc[100, 1, int16be]
+resource typeres0[bool8]
+typestruct {
+	f1	bool8
+	f2	bool16
+}
+typeunion [
+	f1	bool8
+	f2	bool16
+]
+
+type type0 int8
+type type0 int8			### type type0 redeclared, previously declared as type alias at errors.txt:197:6
+resource type0[int32]		### type type0 redeclared, previously declared as type alias at errors.txt:197:6
+type0 = 0, 1
+type type1 type1		### type aliases can't refer to other type aliases
+type type2 int8:4		### unexpected ':', only struct fields can be bitfields
+type type3 type2		### unknown type type2
+type type4 const[0]		### wrong number of arguments for type const, expect value, base type
+type type5 typeunion		### typeunion can't be type alias target
+type type6 len[foo, int32]	### len can't be type alias target
+type type7 len[foo]		### len can't be type alias target
+resource typeres1[int32]
+type type8 typeres1		### typeres1 can't be type alias target
+type int8 int8			### type name int8 conflicts with builtin type
+type opt int8			### type uses reserved name opt
+type type9 const[0, int8]
+type type10 type0		### type aliases can't refer to other type aliases
+type type11 typestruct11	### typestruct11 can't be type alias target
+type type12 proc[123, 2, int16, opt]
+type type13 ptr[in, typestruct13]
+type type14 flags[type0, int32]
+type type15 const[0, type0]	### unexpected value type0 for base type argument of const type, expect [int8 int16 int32 int64 int16be int32be int64be intptr]
+type type16 ptr[in, type0]	### type aliases can't refer to other type aliases
+
+typestruct11 {
+	f	type11		### unknown type type11
+}
+
+typestruct12 {
+	f	type11		### unknown type type11
+}
+
+typestruct13 {
+	f1	type9
+	f2	type12
+}
+
+foo$100(a bool8, b bool16)
+foo$101(a type5)		### unknown type type5
+foo$102(a type2)		### unknown type type2
+foo$103(a type0:4)		### type alias type0 with ':'
+foo$104(a type0[opt])		### type alias type0 with arguments
+foo$105() type0
+foo$106() type6			### unknown type type6
+foo$107(a type9, b type12)
+foo$108(a flags[type0])
+foo$109(a ptr[in, type0])