From 2cd1f6e924ed91e30a25cc6621b301aa9b0a3f77 Mon Sep 17 00:00:00 2001
From: Felipe Pena <felipensp@gmail.com>
Date: Sat, 1 Mar 2025 08:08:24 -0300
Subject: [PATCH] checker: add missing check for IfExpr and MatchExpr with no
 valid type (#23832)

---
 vlib/v/checker/if.v                                |  4 ++++
 vlib/v/checker/match.v                             |  4 ++++
 vlib/v/checker/tests/if_expr_with_none_only.out    | 10 ++++++++++
 vlib/v/checker/tests/if_expr_with_none_only.vv     |  3 +++
 vlib/v/checker/tests/match_expr_with_none_only.out | 12 ++++++++++++
 vlib/v/checker/tests/match_expr_with_none_only.vv  |  6 ++++++
 6 files changed, 39 insertions(+)
 create mode 100644 vlib/v/checker/tests/if_expr_with_none_only.out
 create mode 100644 vlib/v/checker/tests/if_expr_with_none_only.vv
 create mode 100644 vlib/v/checker/tests/match_expr_with_none_only.out
 create mode 100644 vlib/v/checker/tests/match_expr_with_none_only.vv

diff --git a/vlib/v/checker/if.v b/vlib/v/checker/if.v
index b3f3ac78f..eecb72628 100644
--- a/vlib/v/checker/if.v
+++ b/vlib/v/checker/if.v
@@ -575,6 +575,10 @@ fn (mut c Checker) if_expr(mut node ast.IfExpr) ast.Type {
 			c.returns = false
 		}
 	}
+	if node.typ == ast.none_type {
+		c.error('invalid if expression, must supply at least one value other than `none`',
+			node.pos)
+	}
 	// if only untyped literals were given default to int/f64
 	node.typ = ast.mktyp(node.typ)
 	if expr_required && !node.has_else {
diff --git a/vlib/v/checker/match.v b/vlib/v/checker/match.v
index ba49aef36..2b4bc0451 100644
--- a/vlib/v/checker/match.v
+++ b/vlib/v/checker/match.v
@@ -245,6 +245,10 @@ fn (mut c Checker) match_expr(mut node ast.MatchExpr) ast.Type {
 			c.returns = false
 		}
 	}
+	if ret_type == ast.none_type {
+		c.error('invalid match expression, must supply at least one value other than `none`',
+			node.pos)
+	}
 	node.return_type = ret_type
 	cond_var := c.get_base_name(&node.cond)
 	if cond_var != '' {
diff --git a/vlib/v/checker/tests/if_expr_with_none_only.out b/vlib/v/checker/tests/if_expr_with_none_only.out
new file mode 100644
index 000000000..b0350ccb7
--- /dev/null
+++ b/vlib/v/checker/tests/if_expr_with_none_only.out
@@ -0,0 +1,10 @@
+vlib/v/checker/tests/if_expr_with_none_only.vv:2:2: warning: unused variable: `a`
+    1 | fn main() {
+    2 |     a := if true { none } else { none }
+      |     ^
+    3 | }
+vlib/v/checker/tests/if_expr_with_none_only.vv:2:7: error: invalid if expression, must supply at least one value other than `none`
+    1 | fn main() {
+    2 |     a := if true { none } else { none }
+      |          ~~
+    3 | }
diff --git a/vlib/v/checker/tests/if_expr_with_none_only.vv b/vlib/v/checker/tests/if_expr_with_none_only.vv
new file mode 100644
index 000000000..88685686d
--- /dev/null
+++ b/vlib/v/checker/tests/if_expr_with_none_only.vv
@@ -0,0 +1,3 @@
+fn main() {
+	a := if true { none } else { none }
+}
diff --git a/vlib/v/checker/tests/match_expr_with_none_only.out b/vlib/v/checker/tests/match_expr_with_none_only.out
new file mode 100644
index 000000000..c1226c5ff
--- /dev/null
+++ b/vlib/v/checker/tests/match_expr_with_none_only.out
@@ -0,0 +1,12 @@
+vlib/v/checker/tests/match_expr_with_none_only.vv:2:2: warning: unused variable: `a`
+    1 | fn main() {
+    2 |     a := match 1 {
+      |     ^
+    3 |         1 { none }
+    4 |         else { none }
+vlib/v/checker/tests/match_expr_with_none_only.vv:2:7: error: invalid match expression, must supply at least one value other than `none`
+    1 | fn main() {
+    2 |     a := match 1 {
+      |          ~~~~~~~~~
+    3 |         1 { none }
+    4 |         else { none }
diff --git a/vlib/v/checker/tests/match_expr_with_none_only.vv b/vlib/v/checker/tests/match_expr_with_none_only.vv
new file mode 100644
index 000000000..b4936ca42
--- /dev/null
+++ b/vlib/v/checker/tests/match_expr_with_none_only.vv
@@ -0,0 +1,6 @@
+fn main() {
+	a := match 1 {
+		1 { none }
+		else { none }
+	}
+}
-- 
2.39.5