checker, cgen: fix match expr with result (#15706)

vlib/v/checker/match.v

@@ -61,6 +61,7 @@ pub fn (mut c Checker) match_expr(mut node ast.MatchExpr) ast.Type {
 				expr_type := c.expr(stmt.expr)
 				if first_iteration {
 					if node.is_expr && (node.expected_type.has_flag(.optional)
+						|| node.expected_type.has_flag(.result)
 						|| c.table.type_kind(node.expected_type) in [.sum_type, .multi_return]) {
 						ret_type = node.expected_type
 					} else {

vlib/v/gen/c/cgen.v

@@ -116,7 +116,9 @@ mut:
 	inside_map_index          bool
 	inside_opt_data           bool
 	inside_if_optional        bool
+	inside_if_result          bool
 	inside_match_optional     bool
+	inside_match_result       bool
 	inside_vweb_tmpl          bool
 	inside_return             bool
 	inside_struct_init        bool
@@ -1592,6 +1594,29 @@ fn (mut g Gen) stmts_with_tmp_var(stmts []ast.Stmt, tmp_var string) bool {
 						g.writeln(' }, ($c.option_name*)(&$tmp_var), sizeof($styp));')
 					}
 				}
+			} else if g.inside_if_result || g.inside_match_result {
+				g.set_current_pos_as_last_stmt_pos()
+				g.skip_stmt_pos = true
+				if stmt is ast.ExprStmt {
+					if stmt.typ == ast.error_type_idx {
+						g.writeln('${tmp_var}.is_error = true;')
+						g.write('${tmp_var}.err = ')
+						g.expr(stmt.expr)
+						g.writeln(';')
+					} else {
+						mut styp := g.base_type(stmt.typ)
+						$if tinyc && x32 && windows {
+							if stmt.typ == ast.int_literal_type {
+								styp = 'int'
+							} else if stmt.typ == ast.float_literal_type {
+								styp = 'f64'
+							}
+						}
+						g.write('opt_ok2(&($styp[]) { ')
+						g.stmt(stmt)
+						g.writeln(' }, ($c.result_name*)(&$tmp_var), sizeof($styp));')
+					}
+				}
 			} else {
 				g.set_current_pos_as_last_stmt_pos()
 				g.skip_stmt_pos = true
@@ -1609,7 +1634,8 @@ fn (mut g Gen) stmts_with_tmp_var(stmts []ast.Stmt, tmp_var string) bool {
 			}
 		} else {
 			g.stmt(stmt)
-			if (g.inside_if_optional || g.inside_match_optional) && stmt is ast.ExprStmt {
+			if (g.inside_if_optional || g.inside_if_result || g.inside_match_optional
+				|| g.inside_match_result) && stmt is ast.ExprStmt {
 				g.writeln(';')
 			}
 		}
@@ -1796,7 +1822,8 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 			// g.autofree_call_postgen()
 			// }
 			if g.inside_ternary == 0 && !g.inside_if_optional && !g.inside_match_optional
-				&& !node.is_expr && node.expr !is ast.IfExpr {
+				&& !g.inside_if_result && !g.inside_match_result && !node.is_expr
+				&& node.expr !is ast.IfExpr {
 				if node.expr is ast.MatchExpr {
 					g.writeln('')
 				} else {

vlib/v/gen/c/match.v

@@ -12,7 +12,7 @@ fn (mut g Gen) need_tmp_var_in_match(node ast.MatchExpr) bool {
 		if g.table.type_kind(node.return_type) == .sum_type {
 			return true
 		}
-		if node.return_type.has_flag(.optional) {
+		if node.return_type.has_flag(.optional) || node.return_type.has_flag(.result) {
 			return true
 		}
 		if sym.kind == .multi_return {
@@ -52,12 +52,20 @@ fn (mut g Gen) match_expr(node ast.MatchExpr) {
 	if is_expr && !need_tmp_var {
 		g.inside_ternary++
 	}
-	if is_expr && node.return_type.has_flag(.optional) {
-		old := g.inside_match_optional
-		defer {
-			g.inside_match_optional = old
+	if is_expr {
+		if node.return_type.has_flag(.optional) {
+			old := g.inside_match_optional
+			defer {
+				g.inside_match_optional = old
+			}
+			g.inside_match_optional = true
+		} else if node.return_type.has_flag(.result) {
+			old := g.inside_match_result
+			defer {
+				g.inside_match_result = old
+			}
+			g.inside_match_result = true
 		}
-		g.inside_match_optional = true
 	}
 	if node.cond in [ast.Ident, ast.SelectorExpr, ast.IntegerLiteral, ast.StringLiteral, ast.FloatLiteral] {
 		cond_var = g.expr_string(node.cond)

vlib/v/tests/match_expr_with_result_test.v

@@ -0,0 +1,23 @@
+fn foo(i int) ?bool {
+	return match true {
+		i == 0 { true }
+		else { none }
+	}
+}
+
+fn bar(i int) !bool {
+	return match true {
+		i == 0 { true }
+		else { error('') }
+	}
+}
+
+fn test_match_expr_with_result() {
+	r1 := foo(0) or { false }
+	println(r1)
+	assert r1
+
+	r2 := bar(0) or { false }
+	println(r2)
+	assert r2
+}