checker: fix .variant smartcast on non-comptime variables (#20575)

vlib/v/checker/checker.v

@@ -3884,7 +3884,7 @@ fn (mut c Checker) smartcast(mut expr ast.Expr, cur_type ast.Type, to_type_ ast.
 					orig_type = expr.obj.typ
 				}
 				is_inherited = expr.obj.is_inherited
-				ct_type_var = if is_comptime && expr.obj.ct_type_var != .no_comptime {
+				ct_type_var = if is_comptime {
 					.smartcast
 				} else {
 					.no_comptime

vlib/v/debug/tests/comptime_variant.expect

@@ -1,9 +1,13 @@
 #!/usr/bin/env expect
 source "common.tcl"
 
-expect "Break on * comptime_variant_int in ${test_file}:7"
-expect "${test_file}:7 vdbg> "
-send "p a\n"
-expect "a = 0 (int)"
+expect "Break on * comptime_variant in ${test_file}:6"
+expect "${test_file}:6 vdbg> "
+send "p arg\n"
+expect "arg = 0 (int)"
+send "c\n"
+expect "${test_file}:6 vdbg> "
+send "p arg\n"
+expect "arg = foo (string)"
 send "q\n"
 expect eof

vlib/v/debug/tests/comptime_variant.vv

@@ -1,15 +1,15 @@
 type MySum = int | string
 
-fn comptime_variant_int() {
-	a := MySum(int(0))
-	$for v in MySum.variants {
-		if a is v {
+fn comptime_variant(arg MySum) {
+	$for v in arg.variants {
+		if arg is v {
 			$dbg;
-			dump(a)
+			dump(arg)
 		}
 	}
 }
 
 fn main() {
-	comptime_variant_int()
+	comptime_variant(MySum(int(0)))
+	comptime_variant(MySum('foo'))
 }

vlib/v/gen/c/cgen.v

@@ -3937,7 +3937,13 @@ fn (mut g Gen) debugger_stmt(node ast.DebuggerStmt) {
 		if obj.name !in vars {
 			if obj is ast.Var && obj.pos.pos < node.pos.pos {
 				keys.write_string('_SLIT("${obj.name}")')
-				var_typ := if obj.smartcasts.len > 0 { obj.smartcasts.last() } else { obj.typ }
+				var_typ := if obj.ct_type_var != .no_comptime {
+					g.comptime.get_comptime_var_type(ast.Ident{ obj: obj })
+				} else if obj.smartcasts.len > 0 {
+					obj.smartcasts.last()
+				} else {
+					obj.typ
+				}
 				values.write_string('{.typ=_SLIT("${g.table.type_to_str(g.unwrap_generic(var_typ))}"),.value=')
 				obj_sym := g.table.sym(obj.typ)
 				cast_sym := g.table.sym(var_typ)

vlib/v/tests/comptime_smartcast_var_test.v

@@ -0,0 +1,22 @@
+type TestSum = bool | f64 | int | string
+
+fn test_main() {
+	a := TestSum(true)
+	$for v in TestSum.variants {
+		if a is v {
+			$if a is bool {
+				assert a == true
+			}
+			$if a is string {
+				assert a == ''
+			}
+			$if a is f64 {
+				assert a == 0
+			}
+			$if a is int {
+				assert a == 0
+			}
+		}
+	}
+	assert true
+}