v: allow shared anon struct + fix shared struct field initialization with no default value (#23448)

vlib/v/ast/types.v

@@ -169,6 +169,7 @@ pub mut:
 	is_minify      bool
 	is_anon        bool
 	is_generic     bool
+	is_shared      bool
 	has_option     bool // contains any option field
 	generic_types  []Type
 	concrete_types []Type

vlib/v/fmt/struct.v

@@ -153,6 +153,9 @@ fn (mut f Fmt) write_anon_struct_field_decl(field_typ ast.Type, field_anon_decl
 			info := sym.info as ast.Struct
 			if info.is_anon {
 				f.indent++
+				if info.is_shared {
+					f.write('shared ')
+				}
 				f.struct_decl(field_anon_decl, true)
 				f.indent--
 				return true

vlib/v/gen/c/auto_str_methods.v

@@ -1008,7 +1008,11 @@ fn (mut g Gen) gen_str_for_struct(info ast.Struct, lang ast.Language, styp strin
 		} else {
 			''
 		}
-		base_fmt := g.type_to_fmt(g.unwrap_generic(field.typ))
+		mut base_typ := g.unwrap_generic(field.typ)
+		if base_typ.has_flag(.shared_f) {
+			base_typ = base_typ.clear_flag(.shared_f).deref()
+		}
+		base_fmt := g.type_to_fmt(base_typ)
 		is_opt_field := field.typ.has_flag(.option)
 
 		// manage prefix and quote symbol for the filed
@@ -1194,7 +1198,7 @@ fn struct_auto_str_func(sym &ast.TypeSymbol, lang ast.Language, _field_type ast.
 		if !field_type.is_ptr() && field_type.has_option_or_result() {
 			method_str = '(*(${sym.name}*)it${op}${final_field_name}.data)'
 		} else {
-			method_str = 'it${op}${final_field_name}'
+			method_str = 'it${op}${final_field_name}${sufix}'
 		}
 		if sym.kind == .bool {
 			return '${method_str} ? _SLIT("true") : _SLIT("false")', false

vlib/v/gen/c/struct.v

@@ -414,6 +414,14 @@ fn (mut g Gen) get_embed_field_name(field_type ast.Type, field_name string) stri
 	return s
 }
 
+fn (mut g Gen) init_shared_field(field ast.StructField) {
+	field_typ := field.typ.deref()
+	shared_styp := g.styp(field_typ)
+	g.write('(${shared_styp}*)__dup${shared_styp}(&(${shared_styp}){.mtx= {0}, .val=')
+	g.write(g.type_default(field_typ.clear_flag(.shared_f)))
+	g.write('}, sizeof(${shared_styp}))')
+}
+
 fn (mut g Gen) zero_struct_field(field ast.StructField) bool {
 	old_inside_cast_in_heap := g.inside_cast_in_heap
 	g.inside_cast_in_heap = 0
@@ -428,6 +436,11 @@ fn (mut g Gen) zero_struct_field(field ast.StructField) bool {
 			return false
 		} else if !field.has_default_expr {
 			mut has_option_field := false
+			if sym.info.is_shared || field.typ.has_flag(.shared_f) {
+				g.write('.${field_name} = ')
+				g.init_shared_field(field)
+				return true
+			}
 			for fd in sym.info.fields {
 				if fd.typ.has_flag(.option) {
 					has_option_field = true
@@ -520,6 +533,8 @@ fn (mut g Gen) zero_struct_field(field ast.StructField) bool {
 			}
 		}
 		g.write('}')
+	} else if field.typ.has_flag(.shared_f) {
+		g.init_shared_field(field)
 	} else {
 		g.write(g.type_default(field.typ))
 	}
@@ -570,7 +585,11 @@ fn (mut g Gen) struct_decl(s ast.Struct, name string, is_anon bool) {
 		}
 	}
 	if is_anon {
-		g.type_definitions.write_string('\t${name} ')
+		if s.is_shared {
+			g.type_definitions.write_string('\t__shared__${name}* ')
+		} else {
+			g.type_definitions.write_string('\t${name} ')
+		}
 		return
 	} else if s.is_union {
 		if g.is_cc_msvc && aligned_attr != '' {

vlib/v/parser/struct.v

@@ -13,10 +13,15 @@ fn (mut p Parser) struct_decl(is_anon bool) ast.StructDecl {
 	attrs := p.attrs
 	start_pos := p.tok.pos()
 	mut is_pub := p.tok.kind == .key_pub
+	mut is_shared := p.tok.kind == .key_shared
 	if is_pub {
 		p.next()
 	}
 	if is_anon {
+		if is_shared {
+			p.register_auto_import('sync')
+			p.next()
+		}
 		is_pub = true
 	}
 	is_union := p.tok.kind == .key_union
@@ -236,12 +241,18 @@ fn (mut p Parser) struct_decl(is_anon bool) ast.StructDecl {
 				// struct field
 				field_name = p.check_name()
 				p.inside_struct_field_decl = true
-				if p.tok.kind == .key_struct {
+				if p.tok.kind == .key_struct
+					|| (p.tok.kind == .key_shared && p.peek_tok.kind == .key_struct) {
 					// Anon structs
+					field_is_shared := p.tok.kind == .key_shared
 					p.anon_struct_decl = p.struct_decl(true)
 					p.anon_struct_decl.language = language
 					// Find the registered anon struct type, it was registered above in `p.struct_decl()`
 					typ = p.table.find_type_idx(p.anon_struct_decl.name)
+					if field_is_shared {
+						typ = typ.set_flag(.shared_f)
+						typ = typ.set_nr_muls(1)
+					}
 				} else {
 					start_type_pos := p.tok.pos()
 					typ = p.parse_type()
@@ -379,6 +390,7 @@ fn (mut p Parser) struct_decl(is_anon bool) ast.StructDecl {
 			generic_types: generic_types
 			attrs:         attrs
 			is_anon:       is_anon
+			is_shared:     is_shared
 			has_option:    has_option
 		}
 		is_pub:     is_pub

vlib/v/tests/structs/struct_field_shared_test.v

@@ -0,0 +1,26 @@
+struct Foo {
+	bar shared struct {
+	mut:
+		foo int
+		bar int
+	}
+	baz shared int
+}
+
+fn test_main() {
+	assert Foo{}.str() == 'Foo{
+    bar: struct {
+        foo: 0
+        bar: 0
+    }
+    baz: 0
+}'
+	mut t := Foo{}
+	lock t.bar {
+		t.bar.foo = 1
+		t.bar.bar = 2
+	}
+	rlock t.bar {
+		assert t.bar.foo + t.bar.bar == 3
+	}
+}