From cd152169e8792d07ce8ef5403f397f2dc4721610 Mon Sep 17 00:00:00 2001
From: Felipe Pena <felipensp@gmail.com>
Date: Sun, 21 Sep 2025 02:42:35 -0300
Subject: [PATCH] markused: fix or block handling and result propagation from
 indexexpr (fix #25339) (#25356)

---
 vlib/v/markused/walker.v                             | 11 ++++++-----
 vlib/v/tests/skip_unused/ident_or_block.run.out      |  1 +
 .../skip_unused/ident_or_block.skip_unused.run.out   |  1 +
 vlib/v/tests/skip_unused/ident_or_block.vv           | 12 ++++++++++++
 .../skip_unused/indexexpr_result_propagation.run.out |  1 +
 .../indexexpr_result_propagation.skip_unused.run.out |  1 +
 .../skip_unused/indexexpr_result_propagation.vv      | 12 ++++++++++++
 7 files changed, 34 insertions(+), 5 deletions(-)
 create mode 100644 vlib/v/tests/skip_unused/ident_or_block.run.out
 create mode 100644 vlib/v/tests/skip_unused/ident_or_block.skip_unused.run.out
 create mode 100644 vlib/v/tests/skip_unused/ident_or_block.vv
 create mode 100644 vlib/v/tests/skip_unused/indexexpr_result_propagation.run.out
 create mode 100644 vlib/v/tests/skip_unused/indexexpr_result_propagation.skip_unused.run.out
 create mode 100644 vlib/v/tests/skip_unused/indexexpr_result_propagation.vv

diff --git a/vlib/v/markused/walker.v b/vlib/v/markused/walker.v
index ce63ea569..6b7bfc48f 100644
--- a/vlib/v/markused/walker.v
+++ b/vlib/v/markused/walker.v
@@ -53,7 +53,7 @@ mut:
 	uses_ct_variants           bool // $for .variants
 	uses_ct_attribute          bool // $for .attributes
 	uses_external_type         bool
-	uses_err                   bool // err var
+	uses_err_block             bool // or { err var }
 	uses_asserts               bool // assert
 	uses_map_update            bool // has {...expr}
 	uses_debugger              bool // has debugger;
@@ -547,7 +547,7 @@ fn (mut w Walker) expr(node_ ast.Expr) {
 		ast.IndexExpr {
 			w.expr(node.left)
 			w.expr(node.index)
-			if node.or_expr.kind == .block {
+			if node.or_expr.kind != .absent {
 				w.uses_index_check = true
 			}
 			w.mark_by_type(node.typ)
@@ -709,9 +709,6 @@ fn (mut w Walker) expr(node_ ast.Expr) {
 					} else if node.name in w.all_globals {
 						w.mark_global_as_used(node.name)
 					} else {
-						if !w.uses_err && node.name == 'err' {
-							w.uses_err = true
-						}
 						w.fn_by_name(node.name)
 					}
 					if !w.uses_atomic && node.info is ast.IdentVar {
@@ -1105,6 +1102,7 @@ pub fn (mut w Walker) const_fields(cfields []ast.ConstField) {
 @[inline]
 pub fn (mut w Walker) or_block(node ast.OrExpr) {
 	if node.kind == .block {
+		w.uses_err_block = true
 		w.stmts(node.stmts)
 	} else if node.kind == .propagate_option {
 		w.used_option++
@@ -1470,6 +1468,9 @@ fn (mut w Walker) mark_resource_dependencies() {
 			continue
 		}
 	}
+	if w.uses_err_block {
+		w.fn_by_name('error')
+	}
 	if w.uses_guard || w.uses_index_check {
 		w.fn_by_name('error')
 		w.fn_by_name(array_idx_str + '.get_with_check')
diff --git a/vlib/v/tests/skip_unused/ident_or_block.run.out b/vlib/v/tests/skip_unused/ident_or_block.run.out
new file mode 100644
index 000000000..e30f1a968
--- /dev/null
+++ b/vlib/v/tests/skip_unused/ident_or_block.run.out
@@ -0,0 +1 @@
+[vlib/v/tests/skip_unused/ident_or_block.vv:12] set.len: 0
diff --git a/vlib/v/tests/skip_unused/ident_or_block.skip_unused.run.out b/vlib/v/tests/skip_unused/ident_or_block.skip_unused.run.out
new file mode 100644
index 000000000..e30f1a968
--- /dev/null
+++ b/vlib/v/tests/skip_unused/ident_or_block.skip_unused.run.out
@@ -0,0 +1 @@
+[vlib/v/tests/skip_unused/ident_or_block.vv:12] set.len: 0
diff --git a/vlib/v/tests/skip_unused/ident_or_block.vv b/vlib/v/tests/skip_unused/ident_or_block.vv
new file mode 100644
index 000000000..33c83be70
--- /dev/null
+++ b/vlib/v/tests/skip_unused/ident_or_block.vv
@@ -0,0 +1,12 @@
+pub struct Row {
+pub mut:
+	vals []?string
+}
+
+mut set := map[string]bool{}
+rows := []Row{}
+for row in rows {
+	val := row.vals[0]
+	set[val or { 'invariant' }] = true
+}
+dump(set.len)
diff --git a/vlib/v/tests/skip_unused/indexexpr_result_propagation.run.out b/vlib/v/tests/skip_unused/indexexpr_result_propagation.run.out
new file mode 100644
index 000000000..0dc461651
--- /dev/null
+++ b/vlib/v/tests/skip_unused/indexexpr_result_propagation.run.out
@@ -0,0 +1 @@
+[vlib/v/tests/skip_unused/indexexpr_result_propagation.vv:12] set.len: 0
diff --git a/vlib/v/tests/skip_unused/indexexpr_result_propagation.skip_unused.run.out b/vlib/v/tests/skip_unused/indexexpr_result_propagation.skip_unused.run.out
new file mode 100644
index 000000000..0dc461651
--- /dev/null
+++ b/vlib/v/tests/skip_unused/indexexpr_result_propagation.skip_unused.run.out
@@ -0,0 +1 @@
+[vlib/v/tests/skip_unused/indexexpr_result_propagation.vv:12] set.len: 0
diff --git a/vlib/v/tests/skip_unused/indexexpr_result_propagation.vv b/vlib/v/tests/skip_unused/indexexpr_result_propagation.vv
new file mode 100644
index 000000000..3114e1fdf
--- /dev/null
+++ b/vlib/v/tests/skip_unused/indexexpr_result_propagation.vv
@@ -0,0 +1,12 @@
+pub struct Row {
+pub mut:
+	vals []?string
+}
+
+mut set := map[string]bool{}
+rows := []Row{}
+for row in rows {
+	val := row.vals[0]!
+	set[val] = true
+}
+dump(set.len)
-- 
2.39.5