From 738855bb58c1b27aa7ceeddaadbdeb373baf686f Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Tue, 14 Apr 2026 12:45:29 +0300
Subject: [PATCH] checker: asm bad operand with opcode error (fixes #10708)

---
 vlib/v/checker/checker.v                          | 15 +++++++++++++++
 .../tests/asm_mov_requires_two_operands.out       |  7 +++++++
 .../tests/asm_mov_requires_two_operands.vv        |  5 +++++
 3 files changed, 27 insertions(+)
 create mode 100644 vlib/v/checker/tests/asm_mov_requires_two_operands.out
 create mode 100644 vlib/v/checker/tests/asm_mov_requires_two_operands.vv

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 0b9ad2647..620b1162c 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -3883,6 +3883,11 @@ fn (mut c Checker) asm_stmt(mut stmt ast.AsmStmt) {
 				'string', 'asciz', 'ascii'] { // all tcc-supported assembler directives
 				c.error('unknown assembler directive: `${template.name}`', template.pos)
 			}
+		} else if expected_operands := asm_expected_operand_count(stmt.arch, template.name) {
+			if template.args.len != expected_operands {
+				c.error('asm instruction `${template.name}` expects ${expected_operands} operands, but got ${template.args.len}',
+					template.pos)
+			}
 		}
 		for mut arg in template.args {
 			c.asm_arg(arg, stmt, aliases)
@@ -3893,6 +3898,16 @@ fn (mut c Checker) asm_stmt(mut stmt ast.AsmStmt) {
 	}
 }
 
+fn asm_expected_operand_count(arch pref.Arch, name string) ?int {
+	if arch !in [.amd64, .i386] {
+		return none
+	}
+	return match name {
+		'mov' { 2 }
+		else { none }
+	}
+}
+
 fn (mut c Checker) asm_arg(arg ast.AsmArg, stmt ast.AsmStmt, aliases []string) {
 	match arg {
 		ast.AsmAlias {}
diff --git a/vlib/v/checker/tests/asm_mov_requires_two_operands.out b/vlib/v/checker/tests/asm_mov_requires_two_operands.out
new file mode 100644
index 000000000..03ee36534
--- /dev/null
+++ b/vlib/v/checker/tests/asm_mov_requires_two_operands.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/asm_mov_requires_two_operands.vv:3:3: error: asm instruction `mov` expects 2 operands, but got 0
+    1 | fn main() {
+    2 |     asm amd64 {
+    3 |         mov
+      |         ~~~
+    4 |     }
+    5 | }
diff --git a/vlib/v/checker/tests/asm_mov_requires_two_operands.vv b/vlib/v/checker/tests/asm_mov_requires_two_operands.vv
new file mode 100644
index 000000000..a92c0c582
--- /dev/null
+++ b/vlib/v/checker/tests/asm_mov_requires_two_operands.vv
@@ -0,0 +1,5 @@
+fn main() {
+	asm amd64 {
+		mov
+	}
+}
-- 
2.39.5