From 40066a5daa1b840f26d872d902936b40b36e5a65 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Uwe=20Kr=C3=BCger?=
 <45282134+UweKrueger@users.noreply.github.com>
Date: Sat, 13 Feb 2021 00:47:37 +0100
Subject: [PATCH] checker: obey [ref_only] tag, allow embedding in other ref
 struct (#8707)

---
 cmd/tools/vtest-self.v                   |  1 +
 vlib/sync/channels.v                     |  2 +-
 vlib/sync/sync_default.c.v               |  3 ++
 vlib/sync/sync_macos.c.v                 |  3 ++
 vlib/sync/sync_windows.c.v               |  3 ++
 vlib/v/README.md                         |  2 +-
 vlib/v/checker/checker.v                 | 39 ++++++++++++-----
 vlib/v/checker/tests/ref_only_struct.out | 35 +++++++++++++++
 vlib/v/checker/tests/ref_only_struct.vv  | 27 ++++++++++++
 vlib/v/gen/c/cgen_test.v                 |  2 +-
 vlib/v/tests/ref_struct_test.v           | 55 ++++++++++++++++++++++++
 vlib/vweb/sse/sse.v                      |  4 +-
 12 files changed, 161 insertions(+), 15 deletions(-)
 create mode 100644 vlib/v/checker/tests/ref_only_struct.out
 create mode 100644 vlib/v/checker/tests/ref_only_struct.vv
 create mode 100644 vlib/v/tests/ref_struct_test.v

diff --git a/cmd/tools/vtest-self.v b/cmd/tools/vtest-self.v
index 150abd9e39..e3d78ef75c 100644
--- a/cmd/tools/vtest-self.v
+++ b/cmd/tools/vtest-self.v
@@ -127,6 +127,7 @@ const (
 		'vlib/v/tests/module_test.v',
 		'vlib/v/tests/operator_overloading_with_string_interpolation_test.v',
 		'vlib/v/tests/orm_sub_struct_test.v',
+		'vlib/v/tests/ref_struct_test.v',
 		'vlib/v/tests/repl/repl_test.v',
 		'vlib/v/tests/semaphore_test.v',
 		'vlib/v/tests/shared_arg_test.v',
diff --git a/vlib/sync/channels.v b/vlib/sync/channels.v
index e260989235..665e24bca4 100644
--- a/vlib/sync/channels.v
+++ b/vlib/sync/channels.v
@@ -529,7 +529,7 @@ pub fn channel_select(mut channels []&Channel, dir []Direction, mut objrefs []vo
 	assert channels.len == dir.len
 	assert dir.len == objrefs.len
 	mut subscr := []Subscription{len: channels.len}
-	mut sem := Semaphore{}
+	mut sem := unsafe { Semaphore{} }
 	sem.init(0)
 	for i, ch in channels {
 		subscr[i].sem = &sem
diff --git a/vlib/sync/sync_default.c.v b/vlib/sync/sync_default.c.v
index 1fa67aa807..b86703a355 100644
--- a/vlib/sync/sync_default.c.v
+++ b/vlib/sync/sync_default.c.v
@@ -28,10 +28,12 @@ fn C.sem_timedwait(voidptr, voidptr) int
 fn C.sem_destroy(voidptr) int
 
 // [init_with=new_mutex] // TODO: implement support for this struct attribute, and disallow Mutex{} from outside the sync.new_mutex() function.
+[ref_only]
 pub struct Mutex {
 	mutex C.pthread_mutex_t
 }
 
+[ref_only]
 pub struct RwMutex {
 	mutex C.pthread_rwlock_t
 }
@@ -40,6 +42,7 @@ struct RwMutexAttr {
 	attr C.pthread_rwlockattr_t
 }
 
+[ref_only]
 struct Semaphore {
 	sem C.sem_t
 }
diff --git a/vlib/sync/sync_macos.c.v b/vlib/sync/sync_macos.c.v
index 8c3e320039..bd9fc7669c 100644
--- a/vlib/sync/sync_macos.c.v
+++ b/vlib/sync/sync_macos.c.v
@@ -31,10 +31,12 @@ fn C.pthread_cond_timedwait(voidptr, voidptr, voidptr) int
 fn C.pthread_cond_destroy(voidptr) int
 
 // [init_with=new_mutex] // TODO: implement support for this struct attribute, and disallow Mutex{} from outside the sync.new_mutex() function.
+[ref_only]
 pub struct Mutex {
 	mutex C.pthread_mutex_t
 }
 
+[ref_only]
 pub struct RwMutex {
 	mutex C.pthread_rwlock_t
 }
@@ -49,6 +51,7 @@ struct CondAttr {
 
 /* MacOSX has no unnamed semaphores and no `timed_wait()` at all
    so we emulate the behaviour with other devices */
+[ref_only]
 struct Semaphore {
 	mtx C.pthread_mutex_t
 	cond C.pthread_cond_t
diff --git a/vlib/sync/sync_windows.c.v b/vlib/sync/sync_windows.c.v
index 2a3e365b10..4bd9f302b6 100644
--- a/vlib/sync/sync_windows.c.v
+++ b/vlib/sync/sync_windows.c.v
@@ -22,16 +22,19 @@ type SHANDLE = voidptr
 //[init_with=new_mutex] // TODO: implement support for this struct attribute, and disallow Mutex{} from outside the sync.new_mutex() function.
 
 // `SRWLOCK` is much more performant that `Mutex` on Windows, so use that in both cases since we don't want to share with other processes
+[ref_only]
 pub struct Mutex {
 mut:
 	mx C.SRWLOCK    // mutex handle
 }
 
+[ref_only]
 pub struct RwMutex {
 mut:
 	mx C.SRWLOCK    // mutex handle
 }
 
+[ref_only]
 struct Semaphore {
 	mtx C.SRWLOCK
 	cond C.CONDITION_VARIABLE
diff --git a/vlib/v/README.md b/vlib/v/README.md
index 65d46f12e7..2787388c8f 100644
--- a/vlib/v/README.md
+++ b/vlib/v/README.md
@@ -34,7 +34,7 @@ a new preference is created:
 ```v
 import v.pref
 
-pref := pref.Preferences{}
+pref := &pref.Preferences{}
 ```
 
 and a new scope is created:
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 78f38fa694..878ec0a4ef 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -60,6 +60,7 @@ pub mut:
 	inside_unsafe     bool
 	inside_const      bool
 	inside_anon_fn    bool
+	inside_ref_lit    bool
 	skip_flags        bool // should `#flag` and `#include` be skipped
 	cur_generic_types []table.Type
 mut:
@@ -372,13 +373,6 @@ pub fn (mut c Checker) interface_decl(decl ast.InterfaceDecl) {
 					field.type_pos)
 			}
 		}
-		if sym.kind == .struct_ {
-			info := sym.info as table.Struct
-			if info.is_ref_only && !field.typ.is_ptr() {
-				c.error('`$sym.name` type can only be used as a reference: `&$sym.name`',
-					field.type_pos)
-			}
-		}
 		if sym.kind == .map {
 			info := sym.map_info()
 			key_sym := c.table.get_type_symbol(info.key_type)
@@ -403,6 +397,11 @@ pub fn (mut c Checker) struct_decl(mut decl ast.StructDecl) {
 			embed_sym := c.table.get_type_symbol(embed.typ)
 			if embed_sym.kind != .struct_ {
 				c.error('`$embed_sym.name` is not a struct', embed.pos)
+			} else {
+				info := embed_sym.info as table.Struct
+				if info.is_ref_only && !embed.typ.is_ptr() {
+					struct_sym.info.is_ref_only = true
+				}
 			}
 		}
 		for attr in decl.attrs {
@@ -445,8 +444,7 @@ pub fn (mut c Checker) struct_decl(mut decl ast.StructDecl) {
 			if sym.kind == .struct_ {
 				info := sym.info as table.Struct
 				if info.is_ref_only && !field.typ.is_ptr() {
-					c.error('`$sym.name` type can only be used as a reference: `&$sym.name`',
-						field.type_pos)
+					struct_sym.info.is_ref_only = true
 				}
 			}
 			if sym.kind == .map {
@@ -545,6 +543,10 @@ pub fn (mut c Checker) struct_init(mut struct_init ast.StructInit) table.Type {
 			c.error('struct `$type_sym.name` is declared with a `[noinit]` attribute, so ' +
 				'it cannot be initialized with `$type_sym.name{}`', struct_init.pos)
 		}
+		if info.is_ref_only && !c.inside_ref_lit && !c.inside_unsafe && !struct_init.typ.is_ptr() {
+			c.error('`$type_sym.name` type can only be used as a reference `&$type_sym.name` or inside a `struct` reference',
+				struct_init.pos)
+		}
 	}
 	if type_sym.name.len == 1 && c.cur_fn.generic_params.len == 0 {
 		c.error('unknown struct `$type_sym.name`', struct_init.pos)
@@ -2610,7 +2612,14 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 			}
 		}
 		if assign_stmt.right_types.len < assign_stmt.left.len { // first type or multi return types added above
+			old_inside_ref_lit := c.inside_ref_lit
+			if left is ast.Ident {
+				if left.info is ast.IdentVar {
+					c.inside_ref_lit = c.inside_ref_lit || left.info.share == .shared_t
+				}
+			}
 			right_type := c.expr(assign_stmt.right[i])
+			c.inside_ref_lit = old_inside_ref_lit
 			if assign_stmt.right_types.len == i {
 				assign_stmt.right_types << c.check_expr_opt_call(assign_stmt.right[i],
 					right_type)
@@ -2875,7 +2884,14 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 		left_first := assign_stmt.left[0]
 		if left_first is ast.Ident {
 			assigned_var := left_first
+			mut is_shared := false
+			if left_first.info is ast.IdentVar {
+				is_shared = left_first.info.share == .shared_t
+			}
+			old_inside_ref_lit := c.inside_ref_lit
+			c.inside_ref_lit = (c.inside_ref_lit || node.op == .amp || is_shared)
 			c.expr(node.right)
+			c.inside_ref_lit = old_inside_ref_lit
 			if node.right is ast.Ident {
 				if node.right.obj is ast.Var {
 					v := node.right.obj
@@ -3921,7 +3937,7 @@ fn (mut c Checker) comptime_call(mut node ast.ComptimeCall) table.Type {
 	if node.is_vweb {
 		// TODO assoc parser bug
 		pref_ := *c.pref
-		pref2 := pref.Preferences{
+		pref2 := &pref.Preferences{
 			...pref_
 			is_vweb: true
 		}
@@ -5121,7 +5137,10 @@ pub fn (mut c Checker) postfix_expr(mut node ast.PostfixExpr) table.Type {
 }
 
 pub fn (mut c Checker) prefix_expr(mut node ast.PrefixExpr) table.Type {
+	old_inside_ref_lit := c.inside_ref_lit
+	c.inside_ref_lit = c.inside_ref_lit || node.op == .amp
 	right_type := c.expr(node.right)
+	c.inside_ref_lit = old_inside_ref_lit
 	node.right_type = right_type
 	// TODO: testing ref/deref strategy
 	if node.op == .amp && !right_type.is_ptr() {
diff --git a/vlib/v/checker/tests/ref_only_struct.out b/vlib/v/checker/tests/ref_only_struct.out
new file mode 100644
index 0000000000..b9ac13b0f9
--- /dev/null
+++ b/vlib/v/checker/tests/ref_only_struct.out
@@ -0,0 +1,35 @@
+vlib/v/checker/tests/ref_only_struct.vv:18:7: error: `Abc` type can only be used as a reference `&Abc` or inside a `struct` reference
+   16 | 
+   17 | fn main() {
+   18 |     a := Abc{ n: 3 }
+      |          ~~~~~~~~~~~
+   19 |     b := St{
+   20 |         Abc{ n: 7 }
+vlib/v/checker/tests/ref_only_struct.vv:19:7: error: `St` type can only be used as a reference `&St` or inside a `struct` reference
+   17 | fn main() {
+   18 |     a := Abc{ n: 3 }
+   19 |     b := St{
+      |          ~~~
+   20 |         Abc{ n: 7 }
+   21 |     }
+vlib/v/checker/tests/ref_only_struct.vv:20:3: error: `Abc` type can only be used as a reference `&Abc` or inside a `struct` reference
+   18 |     a := Abc{ n: 3 }
+   19 |     b := St{
+   20 |         Abc{ n: 7 }
+      |         ~~~~~~~~~~~
+   21 |     }
+   22 |     x := Qwe{
+vlib/v/checker/tests/ref_only_struct.vv:22:7: error: `Qwe` type can only be used as a reference `&Qwe` or inside a `struct` reference
+   20 |         Abc{ n: 7 }
+   21 |     }
+   22 |     x := Qwe{
+      |          ~~~~
+   23 |         f: 12.25
+   24 |         a: Abc{ n: 23 }
+vlib/v/checker/tests/ref_only_struct.vv:24:6: error: `Abc` type can only be used as a reference `&Abc` or inside a `struct` reference
+   22 |     x := Qwe{
+   23 |         f: 12.25
+   24 |         a: Abc{ n: 23 }
+      |            ~~~~~~~~~~~~
+   25 |     }
+   26 |     println('$a.n $b.n $x.a.n')
diff --git a/vlib/v/checker/tests/ref_only_struct.vv b/vlib/v/checker/tests/ref_only_struct.vv
new file mode 100644
index 0000000000..0978474d19
--- /dev/null
+++ b/vlib/v/checker/tests/ref_only_struct.vv
@@ -0,0 +1,27 @@
+[ref_only]
+struct Abc {
+mut:
+	n int
+}
+
+struct St {
+	Abc
+}
+
+struct Qwe {
+mut:
+	f f64
+	a Abc
+}
+
+fn main() {
+	a := Abc{ n: 3 }
+	b := St{
+		Abc{ n: 7 }
+	}
+	x := Qwe{
+		f: 12.25
+		a: Abc{ n: 23 }
+	}
+	println('$a.n $b.n $x.a.n')
+}
diff --git a/vlib/v/gen/c/cgen_test.v b/vlib/v/gen/c/cgen_test.v
index 179a5f20ba..1aa5b5de50 100644
--- a/vlib/v/gen/c/cgen_test.v
+++ b/vlib/v/gen/c/cgen_test.v
@@ -19,7 +19,7 @@ fn test_c_files() {
 	for i in 1 .. (nr_tests + 1) {
 		path := '$vroot/vlib/v/gen/tests/${i}.vv'
 		ctext := os.read_file('$vroot/vlib/v/gen/tests/${i}.c') or { panic(err) }
-		mut b := builder.new_builder(pref.Preferences{})
+		mut b := builder.new_builder(&pref.Preferences{})
 		b.module_search_paths = ['$vroot/vlib/v/gen/tests/']
 		mut res := b.gen_c([path]).after('#endbuiltin')
 		if res.contains('string _STR') {
diff --git a/vlib/v/tests/ref_struct_test.v b/vlib/v/tests/ref_struct_test.v
new file mode 100644
index 0000000000..c98656ef45
--- /dev/null
+++ b/vlib/v/tests/ref_struct_test.v
@@ -0,0 +1,55 @@
+[ref_only]
+struct Abc {
+mut:
+	n int
+}
+
+struct St {
+	Abc
+}
+
+struct Qwe {
+mut:
+	f f64
+	a Abc
+}
+
+struct Rtz {
+mut:
+	f f64
+	a &Abc
+}
+
+fn test_ref() {
+	a := &Abc{ n: 3 }
+	assert a.n == 3
+}
+
+fn test_shared() {
+	shared a := Abc{ n: 4 }
+	res := rlock a { a.n }
+	assert res == 4
+}
+
+fn test_embed_in_ref_struct() {
+	a := &St{
+		Abc{ n: 5 }
+	}
+	assert a.n == 5
+}
+
+fn test_field_in_ref_struct() {
+	x := &Qwe{
+		f: 12.25
+		a: Abc{ n: 23 }
+	}
+	assert x.a.n == 23
+}
+
+fn test_ref_field() {
+	y := Rtz{
+		f: -6.25
+		a: &Abc{ n: 29 }
+	}
+	assert y.a.n == 29
+}
diff --git a/vlib/vweb/sse/sse.v b/vlib/vweb/sse/sse.v
index 82cd50a04d..f0fe1ffbf3 100644
--- a/vlib/vweb/sse/sse.v
+++ b/vlib/vweb/sse/sse.v
@@ -35,8 +35,8 @@ pub struct SSEMessage {
 	retry int
 }
 
-pub fn new_connection(conn &net.TcpConn) SSEConnection {
-	return SSEConnection{
+pub fn new_connection(conn &net.TcpConn) &SSEConnection {
+	return &SSEConnection{
 		conn: conn
 	}
 }