checker, cgen: fix match branches return type ref mismatch, when the return type exists as interface or sumtype (fix #16203) (#19806)

Author: shove70

vlib/v/checker/checker.v

@@ -3564,9 +3564,7 @@ fn (mut c Checker) ident(mut node ast.Ident) ast.Type {
 							typ = c.expr(mut obj.expr)
 						}
 					}
-					if c.inside_casting_to_str && obj.orig_type != 0
-						&& c.table.sym(obj.orig_type).kind == .interface_
-						&& c.table.sym(obj.smartcasts.last()).kind != .interface_ {
+					if c.inside_casting_to_str && c.is_interface_var(obj) {
 						typ = typ.deref()
 					}
 					is_option := typ.has_flag(.option) || typ.has_flag(.result)
@@ -4028,6 +4026,12 @@ pub fn (mut c Checker) is_comptime_var(node ast.Expr) bool {
 		&& (node.obj as ast.Var).ct_type_var != .no_comptime
 }
 
+[inline]
+fn (mut c Checker) is_interface_var(var ast.ScopeObject) bool {
+	return var is ast.Var && var.orig_type != 0 && c.table.sym(var.orig_type).kind == .interface_
+		&& c.table.sym(var.smartcasts.last()).kind != .interface_
+}
+
 fn (mut c Checker) mark_as_referenced(mut node ast.Expr, as_interface bool) {
 	match mut node {
 		ast.Ident {

vlib/v/checker/match.v

@@ -74,22 +74,51 @@ fn (mut c Checker) match_expr(mut node ast.MatchExpr) ast.Type {
 						ret_type = node.expected_type
 					} else {
 						ret_type = expr_type
+						if expr_type.is_ptr() {
+							if stmt.expr is ast.Ident && stmt.expr.obj is ast.Var
+								&& c.is_interface_var(stmt.expr.obj) {
+								ret_type = expr_type.deref()
+							} else if mut stmt.expr is ast.PrefixExpr
+								&& stmt.expr.right is ast.Ident {
+								ident := stmt.expr.right as ast.Ident
+								if ident.obj is ast.Var && c.is_interface_var(ident.obj) {
+									ret_type = expr_type.deref()
+								}
+							}
+						}
+					}
+				} else {
+					if node.is_expr && ret_type.idx() != expr_type.idx() {
+						if (node.expected_type.has_flag(.option)
+							|| node.expected_type.has_flag(.result))
+							&& c.table.sym(stmt.typ).kind == .struct_
+							&& c.type_implements(stmt.typ, ast.error_type, node.pos) {
+							stmt.expr = ast.CastExpr{
+								expr: stmt.expr
+								typname: 'IError'
+								typ: ast.error_type
+								expr_type: stmt.typ
+								pos: node.pos
+							}
+							stmt.typ = ast.error_type
+						} else {
+							c.check_match_branch_last_stmt(stmt, ret_type, expr_type)
+						}
 					}
-				} else if node.is_expr && ret_type.idx() != expr_type.idx() {
-					if (node.expected_type.has_flag(.option)
-						|| node.expected_type.has_flag(.result))
-						&& c.table.sym(stmt.typ).kind == .struct_
-						&& c.type_implements(stmt.typ, ast.error_type, node.pos) {
-						stmt.expr = ast.CastExpr{
-							expr: stmt.expr
-							typname: 'IError'
-							typ: ast.error_type
-							expr_type: stmt.typ
-							pos: node.pos
+					if node.is_expr && stmt.typ != ast.error_type {
+						ret_sym := c.table.sym(ret_type)
+						stmt_sym := c.table.sym(stmt.typ)
+						if ret_sym.kind !in [.sum_type, .interface_]
+							&& stmt_sym.kind in [.sum_type, .interface_] {
+							c.error('return type mismatch, it should be `${ret_sym.name}`',
+								stmt.pos)
+						}
+						if ret_type.nr_muls() != stmt.typ.nr_muls()
+							&& stmt.typ.idx() !in [ast.voidptr_type_idx, ast.nil_type_idx] {
+							type_name := '&'.repeat(ret_type.nr_muls()) + ret_sym.name
+							c.error('return type mismatch, it should be `${type_name}`',
+								stmt.pos)
 						}
-						stmt.typ = ast.error_type
-					} else {
-						c.check_match_branch_last_stmt(stmt, ret_type, expr_type)
 					}
 				}
 			} else if stmt !in [ast.Return, ast.BranchStmt] {

vlib/v/checker/tests/match_return_mismatch_type_err.out

@@ -1,7 +1,42 @@
+vlib/v/checker/tests/match_return_mismatch_type_err.vv:27:6: warning: cannot assign a reference to a value (this will be an error soon) left=string false right=string true ptr=true
+   25 | 
+   26 |     mut res := ''
+   27 |     res = match any {
+      |         ^
+   28 |         string { &any }
+   29 |         else { &variable }
 vlib/v/checker/tests/match_return_mismatch_type_err.vv:4:10: error: return type mismatch, it should be `string`
     2 |     a := match 1 {
     3 |         1 { 'aa' }
     4 |         else { 22 }
       |                ~~
     5 |     }
     6 |     println(a)
+vlib/v/checker/tests/match_return_mismatch_type_err.vv:18:10: error: return type mismatch, it should be `&string`
+   16 |     _ = match any {
+   17 |         string { &any }
+   18 |         else { variable }
+      |                ~~~~~~~~
+   19 |     }
+   20 |
+vlib/v/checker/tests/match_return_mismatch_type_err.vv:23:10: error: return type mismatch, it should be `string`
+   21 |     _ = match any {
+   22 |         string { any }
+   23 |         else { &variable }
+      |                ^
+   24 |     }
+   25 |
+vlib/v/checker/tests/match_return_mismatch_type_err.vv:43:10: error: return type mismatch, it should be `&string`
+   41 |     _ = match any {
+   42 |         string { &any }
+   43 |         else { variable }
+      |                ~~~~~~~~
+   44 |     }
+   45 |
+vlib/v/checker/tests/match_return_mismatch_type_err.vv:48:10: error: return type mismatch, it should be `string`
+   46 |     _ = match any {
+   47 |         string { any }
+   48 |         else { &variable }
+      |                ^
+   49 |     }
+   50 | }

vlib/v/checker/tests/match_return_mismatch_type_err.vv

@@ -5,3 +5,46 @@ fn main() {
 	}
 	println(a)
 }
+
+// for test the returns both interface or non-interface
+interface IAny {}
+
+fn returns_both_interface_and_non_interface() {
+	any := IAny('abc')
+	variable := ''
+
+	_ = match any {
+		string { &any }
+		else { variable }
+	}
+
+	_ = match any {
+		string { any }
+		else { &variable }
+	}
+
+	mut res := ''
+	res = match any {
+		string { &any }
+		else { &variable }
+	}
+	println(res)
+}
+
+// for test the returns both sumtype or non-sumtype
+type SAny = int | string
+
+fn returns_both_sumtype_and_non_sumtype() {
+	any := SAny('abc')
+	variable := ''
+
+	_ = match any {
+		string { &any }
+		else { variable }
+	}
+
+	_ = match any {
+		string { any }
+		else { &variable }
+	}
+}

vlib/v/gen/c/cgen.v

@@ -4349,6 +4349,12 @@ fn (mut g Gen) get_const_name(node ast.Ident) string {
 	}
 }
 
+[inline]
+fn (mut g Gen) is_interface_var(var ast.ScopeObject) bool {
+	return var is ast.Var && var.orig_type != 0 && g.table.sym(var.orig_type).kind == .interface_
+		&& g.table.sym(var.smartcasts.last()).kind != .interface_
+}
+
 fn (mut g Gen) ident(node ast.Ident) {
 	prevent_sum_type_unwrapping_once := g.prevent_sum_type_unwrapping_once
 	g.prevent_sum_type_unwrapping_once = false
@@ -4485,9 +4491,7 @@ fn (mut g Gen) ident(node ast.Ident) {
 						g.write('(')
 						if obj_sym.kind == .sum_type && !is_auto_heap {
 							g.write('*')
-						} else if g.inside_casting_to_str && node.obj.orig_type != 0
-							&& g.table.sym(node.obj.orig_type).kind == .interface_
-							&& g.table.sym(node.obj.smartcasts.last()).kind != .interface_ {
+						} else if g.inside_casting_to_str && g.is_interface_var(node.obj) {
 							g.write('*')
 						}
 					}

vlib/v/gen/c/match.v

@@ -230,7 +230,23 @@ fn (mut g Gen) match_expr_sumtype(node ast.MatchExpr, is_expr bool, cond_var str
 			if is_expr && tmp_var.len > 0 && g.table.sym(node.return_type).kind == .sum_type {
 				g.expected_cast_type = node.return_type
 			}
+			inside_casting_to_str_old := g.inside_casting_to_str
+			if is_expr && branch.stmts.len > 0 {
+				mut stmt := branch.stmts.last()
+				if mut stmt is ast.ExprStmt {
+					if mut stmt.expr is ast.Ident && stmt.expr.obj is ast.Var
+						&& g.is_interface_var(stmt.expr.obj) {
+						g.inside_casting_to_str = true
+					} else if mut stmt.expr is ast.PrefixExpr && stmt.expr.right is ast.Ident {
+						ident := stmt.expr.right as ast.Ident
+						if ident.obj is ast.Var && g.is_interface_var(ident.obj) {
+							g.inside_casting_to_str = true
+						}
+					}
+				}
+			}
 			g.stmts_with_tmp_var(branch.stmts, tmp_var)
+			g.inside_casting_to_str = inside_casting_to_str_old
 			g.expected_cast_type = 0
 			if g.inside_ternary == 0 {
 				g.writeln('}')

vlib/v/tests/match_test.v

@@ -301,3 +301,23 @@ fn test_noreturn() {
 		}
 	}
 }
+
+// for test the returns both interface and non-interface
+interface Any {}
+
+fn test_returns_both_interface_and_non_interface() {
+	any := Any('abc')
+
+	mut res := match any {
+		string { any }
+		else { 'literal' }
+	}
+	assert res == 'abc'
+
+	variable := ''
+	res = match any {
+		string { any }
+		else { variable }
+	}
+	assert res == 'abc'
+}