cgen: fix compile error on locking interface value (#12883)

vlib/v/gen/c/cgen.v

@@ -183,6 +183,7 @@ mut:
 	force_main_console  bool // true when [console] used on fn main()
 	as_cast_type_names  map[string]string // table for type name lookup in runtime (for __as_cast)
 	obf_table           map[string]string
+	referenced_fns      shared map[string]bool // functions that have been referenced
 	nr_closures         int
 	expected_cast_type  ast.Type // for match expr of sumtypes
 	anon_fn             bool
@@ -523,6 +524,7 @@ fn cgen_process_one_file_cb(p &pool.PoolProcessor, idx int, wid int) &Gen {
 		threaded_fns: global_g.threaded_fns
 		done_optionals: global_g.done_optionals
 		is_autofree: global_g.pref.autofree
+		referenced_fns: global_g.referenced_fns
 	}
 	g.gen_file()
 	return g
@@ -2353,8 +2355,18 @@ fn (mut g Gen) expr_with_cast(expr ast.Expr, got_type_raw ast.Type, expected_typ
 				'f64' { 'float_literal' }
 				else { got_styp }
 			}
-			exp_styp := exp_sym.cname
+			got_is_shared := got_type.has_flag(.shared_f)
-			mut fname := '/*$exp_sym*/I_${got_styp}_to_Interface_$exp_styp'
+			exp_styp := if got_is_shared { '__shared__$exp_sym.cname' } else { exp_sym.cname }
+			// If it's shared, we need to use the other caster:
+			mut fname := if got_is_shared {
+				'I___shared__${got_styp}_to_shared_Interface_$exp_styp'
+			} else {
+				'I_${got_styp}_to_Interface_$exp_styp'
+			}
+			lock g.referenced_fns {
+				g.referenced_fns[fname] = true
+			}
+			fname = '/*$exp_sym*/$fname'
 			if exp_sym.info.is_generic {
 				fname = g.generic_fn_name(exp_sym.info.concrete_types, fname, false)
 			}
@@ -6497,6 +6509,14 @@ fn (g Gen) as_cast_name_table() string {
 	return name_ast.str()
 }
 
+fn (g Gen) has_been_referenced(fn_name string) bool {
+	mut referenced := false
+	lock g.referenced_fns {
+		referenced = g.referenced_fns[fn_name]
+	}
+	return referenced
+}
+
 // Generates interface table and interface indexes
 fn (mut g Gen) interface_table() string {
 	mut sb := strings.new_builder(100)
@@ -6607,6 +6627,25 @@ fn (mut g Gen) interface_table() string {
 static inline $interface_name I_${cctype}_to_Interface_${interface_name}($cctype* x) {
 	return $cast_struct_str;
 }')
+
+				shared_fn_name := 'I___shared__${cctype}_to_shared_Interface___shared__$interface_name'
+				// Avoid undefined types errors by only generating the converters that are referenced:
+				if g.has_been_referenced(shared_fn_name) {
+					mut cast_shared_struct := strings.new_builder(100)
+					cast_shared_struct.writeln('(__shared__$interface_name) {')
+					cast_shared_struct.writeln('\t\t.mtx = {0},')
+					cast_shared_struct.writeln('\t\t.val = {')
+					cast_shared_struct.writeln('\t\t\t._$cctype = &x->val,')
+					cast_shared_struct.writeln('\t\t\t._typ = $interface_index_name,')
+					cast_shared_struct.writeln('\t\t}')
+					cast_shared_struct.write_string('\t}')
+					cast_shared_struct_str := cast_shared_struct.str()
+					cast_functions.writeln('
+// Casting functions for converting "__shared__$cctype" to interface "__shared__$interface_name"
+static inline __shared__$interface_name ${shared_fn_name}(__shared__$cctype* x) {
+	return $cast_shared_struct_str;
+}')
+				}
 			}
 
 			if g.pref.build_mode != .build_module {
@@ -6685,7 +6724,13 @@ static inline $interface_name I_${cctype}_to_Interface_${interface_name}($cctype
 						typ: st.set_nr_muls(1)
 					}
 					fargs, _, _ := g.fn_args(params, voidptr(0))
-					methods_wrapper.write_string(g.out.cut_last(g.out.len - params_start_pos))
+					mut parameter_name := g.out.cut_last(g.out.len - params_start_pos)
+
+					if st.is_ptr() {
+						parameter_name = parameter_name.trim_left('__shared__')
+					}
+
+					methods_wrapper.write_string(parameter_name)
 					methods_wrapper.writeln(') {')
 					methods_wrapper.write_string('\t')
 					if method.return_type != ast.void_type {
@@ -6703,9 +6748,13 @@ static inline $interface_name I_${cctype}_to_Interface_${interface_name}($cctype
 							methods_wrapper.write_string('->$esym.embed_name()')
 						}
 						methods_wrapper.writeln('${fargs[1..].join(', ')});')
+					} else {
+						if parameter_name.starts_with('__shared__') {
+							methods_wrapper.writeln('${method_call}(${fargs.join(', ')}->val);')
 						} else {
 							methods_wrapper.writeln('${method_call}(*${fargs.join(', ')});')
 						}
+					}
 					methods_wrapper.writeln('}')
 					// .speak = Cat_speak_Interface_Animal_method_wrapper
 					method_call += iwpostfix

vlib/v/gen/c/fn.v

@@ -725,9 +725,17 @@ fn (mut g Gen) method_call(node ast.CallExpr) {
 		$if debug_interface_method_call ? {
 			eprintln('>>> interface typ_sym.name: $typ_sym.name | receiver_type_name: $receiver_type_name | pos: $node.pos')
 		}
+
+		left_is_shared := node.left_type.has_flag(.shared_f)
 		g.write('${c_name(receiver_type_name)}_name_table[')
 		g.expr(node.left)
-		dot := if node.left_type.is_ptr() { '->' } else { '.' }
+		dot := if left_is_shared {
+			'->val.'
+		} else if node.left_type.is_ptr() {
+			'->'
+		} else {
+			'.'
+		}
 		mname := c_name(node.name)
 		g.write('${dot}_typ]._method_${mname}(')
 		g.expr(node.left)

vlib/v/tests/shared_interface_test.v

@@ -0,0 +1,81 @@
+interface MyInterface {
+	foo() string
+}
+
+struct MyStruct {
+pub mut:
+	fooer shared MyInterface
+}
+
+struct MyImplementor {
+	num int
+}
+
+fn (m MyImplementor) foo() string {
+	// Can read member properties:
+	num := m.num
+	return 'Hello World $num!'
+}
+
+fn test_shared_interface_lock_1() {
+	shared imp1 := MyImplementor{
+		num: 1
+	}
+	s1 := MyStruct{
+		fooer: imp1
+	}
+	lock s1.fooer {
+		assert s1.fooer.foo() == 'Hello World 1!'
+	}
+}
+
+fn test_shared_interface_lock_2() {
+	shared imp := MyOtherImplementor{
+		x: 1
+		y: 2
+		s: 'testing'
+	}
+	s := MyStruct{
+		fooer: imp
+	}
+
+	lock s.fooer {
+		assert s.fooer.foo() == 'Hello World (1, 2, testing)!'
+	}
+
+	// Lock is released and can be locked again:
+	lock s.fooer {
+		assert s.fooer.foo() == 'Hello World (1, 2, testing)!'
+	}
+}
+
+// TODO: Fix modifying shared interface value
+// fn test_shared_interface_can_be_modified() {
+// 	shared imp1 := MyImplementor{num: 6}
+// 	shared imp2 := MyOtherImplementor{
+// 		x: 7
+// 		y: 3
+// 		s: 'here be dragons...'
+// 	}
+// 	s := MyStruct{
+// 		fooer: imp1
+// 	}
+// 	lock s.fooer {
+// 		assert(s.fooer.foo() == 'Hello World 6!')
+// 		s.fooer = imp2
+// 	}
+// 	lock s.fooer {
+// 		assert(s.fooer.foo() == 'Hello World (7, 3, here be dragons...)!')
+// 	}
+// }
+
+struct MyOtherImplementor {
+	x int
+	y int
+	s string
+}
+
+fn (m MyOtherImplementor) foo() string {
+	// Different implementation:
+	return 'Hello World ($m.x, $m.y, $m.s)!'
+}