checker: check shared parameter assigning (fix #18525) (#18534)

vlib/v/checker/assign.v

@@ -164,6 +164,12 @@ fn (mut c Checker) assign_stmt(mut node ast.AssignStmt) {
 		mut right := if i < node.right.len { node.right[i] } else { node.right[0] }
 		mut right_type := node.right_types[i]
 		if mut right is ast.Ident {
+			// resolve shared right vairable
+			if right_type.has_flag(.shared_f) {
+				if c.fail_if_unreadable(right, right_type, 'right-hand side of assignment') {
+					return
+				}
+			}
 			right_sym := c.table.sym(right_type)
 			if right_sym.info is ast.Struct {
 				if right_sym.info.generic_types.len > 0 {

vlib/v/checker/checker.v

@@ -4664,7 +4664,8 @@ fn (mut c Checker) ensure_type_exists(typ ast.Type, pos token.Pos) ? {
 	}
 }
 
-fn (mut c Checker) fail_if_unreadable(expr ast.Expr, typ ast.Type, what string) {
+// return true if a violation of a shared variable access rule is detected
+fn (mut c Checker) fail_if_unreadable(expr ast.Expr, typ ast.Type, what string) bool {
 	mut pos := token.Pos{}
 	match expr {
 		ast.Ident {
@@ -4673,9 +4674,10 @@ fn (mut c Checker) fail_if_unreadable(expr ast.Expr, typ ast.Type, what string)
 					action := if what == 'argument' { 'passed' } else { 'used' }
 					c.error('`${expr.name}` is `shared` and must be `rlock`ed or `lock`ed to be ${action} as non-mut ${what}',
 						expr.pos)
+					return true
 				}
 			}
-			return
+			return false
 		}
 		ast.SelectorExpr {
 			pos = expr.pos
@@ -4685,31 +4687,42 @@ fn (mut c Checker) fail_if_unreadable(expr ast.Expr, typ ast.Type, what string)
 					action := if what == 'argument' { 'passed' } else { 'used' }
 					c.error('`${expr_name}` is `shared` and must be `rlock`ed or `lock`ed to be ${action} as non-mut ${what}',
 						expr.pos)
+					return true
 				}
-				return
+				return false
 			} else {
-				c.fail_if_unreadable(expr.expr, expr.expr_type, what)
+				if c.fail_if_unreadable(expr.expr, expr.expr_type, what) {
+					return true
+				}
 			}
 		}
 		ast.CallExpr {
 			pos = expr.pos
 			if expr.is_method {
-				c.fail_if_unreadable(expr.left, expr.left_type, what)
+				if c.fail_if_unreadable(expr.left, expr.left_type, what) {
+					return true
+				}
 			}
-			return
+			return false
 		}
 		ast.LockExpr {
 			// TODO: check expressions inside the lock by appending to c.(r)locked_names
-			return
+			return false
 		}
 		ast.IndexExpr {
 			pos = expr.left.pos().extend(expr.pos)
-			c.fail_if_unreadable(expr.left, expr.left_type, what)
+			if c.fail_if_unreadable(expr.left, expr.left_type, what) {
+				return true
+			}
 		}
 		ast.InfixExpr {
 			pos = expr.left.pos().extend(expr.pos)
-			c.fail_if_unreadable(expr.left, expr.left_type, what)
+			if c.fail_if_unreadable(expr.left, expr.left_type, what) {
-			c.fail_if_unreadable(expr.right, expr.right_type, what)
+				return true
+			}
+			if c.fail_if_unreadable(expr.right, expr.right_type, what) {
+				return true
+			}
 		}
 		else {
 			pos = expr.pos()
@@ -4718,7 +4731,9 @@ fn (mut c Checker) fail_if_unreadable(expr ast.Expr, typ ast.Type, what string)
 	if typ.has_flag(.shared_f) {
 		c.error('you have to create a handle and `rlock` it to use a `shared` element as non-mut ${what}',
 			pos)
+		return true
 	}
+	return false
 }
 
 fn (mut c Checker) fail_if_stack_struct_action_outside_unsafe(mut ident ast.Ident, failed_action string) {

vlib/v/checker/tests/shared_param_assign_err.out

@@ -0,0 +1,13 @@
+vlib/v/checker/tests/shared_param_assign_err.vv:2:10: error: `arr` is `shared` and must be `rlock`ed or `lock`ed to be used as non-mut right-hand side of assignment
+    1 | fn foo(shared arr []string) {
+    2 |     arr2 := arr
+      |             ~~~
+    3 |     println(arr2)
+    4 | }
+vlib/v/checker/tests/shared_param_assign_err.vv:3:10: error: `arr2` is `shared` and must be `rlock`ed or `lock`ed to be used as non-mut argument to print
+    1 | fn foo(shared arr []string) {
+    2 |     arr2 := arr
+    3 |     println(arr2)
+      |             ~~~~
+    4 | }
+    5 |

vlib/v/checker/tests/shared_param_assign_err.vv

@@ -0,0 +1,9 @@
+fn foo(shared arr []string) {
+	arr2 := arr
+	println(arr2)
+}
+
+fn main() {
+	shared arr := ['']
+	foo(shared arr)
+}