cgen: fix bit-field generation for option/result types in minified st… (#26670)

* cgen: fix bit-field generation for option/result types in minified structs (fixes #26622)

Option and result types are represented as structs in C, which cannot be
used as bit-fields. Skip the bit-field optimization for these types in
minified structs to avoid C compilation errors.

Co-authored-by: iFlow CLI <iflow> (glm-5)

* tests: skip minify_option_field test on MSVC

MSVC handles bit-fields differently than GCC/Clang, causing the
minify_option_field test to fail on Windows MSVC CI.

- Add _not_msvc_windows.vv suffix pattern to skip logic
- Rename test files to use the new suffix

This follows the existing naming convention for platform/compiler-
specific test handling (similar to _nix.vv, _msvc_windows.vv).

Author: kbkpbot

vlib/v/gen/c/coutput_test.v

@@ -284,6 +284,12 @@ fn should_skip(relpath string) bool {
 				return true
 			}
 		}
+		$if msvc {
+			if relpath.contains('_not_msvc_windows.vv') {
+				eprintln('> skipping ${relpath} on msvc')
+				return true
+			}
+		}
 	} else {
 		if relpath.contains('_windows.vv') {
 			eprintln('> skipping ${relpath} on !windows')

vlib/v/gen/c/struct.v

@@ -703,7 +703,8 @@ fn (mut g Gen) struct_decl(s ast.Struct, name string, is_anon bool, is_option bo
 			field_name := c_name(field.name)
 			volatile_prefix := if field.is_volatile { 'volatile ' } else { '' }
 			mut size_suffix := ''
-			if is_minify && !g.is_cc_msvc && !g.pref.output_cross_c {
+			if is_minify && !g.is_cc_msvc && !g.pref.output_cross_c && !field.typ.has_flag(.option)
+				&& !field.typ.has_flag(.result) {
 				if field.typ == ast.bool_type_idx {
 					size_suffix = ' : 1'
 				} else {

vlib/v/gen/c/testdata/minify_option_field_not_msvc_windows.c.must_have

@@ -0,0 +1,4 @@
+_option_bool optional;
+main__Status status : 2;
+_option_main__Priority priority;
+bool done : 1;

vlib/v/gen/c/testdata/minify_option_field_not_msvc_windows.out

@@ -0,0 +1,4 @@
+active
+low
+false
+false

vlib/v/gen/c/testdata/minify_option_field_not_msvc_windows.vv

@@ -0,0 +1,35 @@
+// Test that minified structs with option fields don't use bit-fields
+// Bit-fields can only have integral types in C, not struct types
+// Option types are represented as structs in C
+
+module main
+
+enum Status as u8 {
+	pending
+	active
+	inactive
+}
+
+enum Priority as u8 {
+	low
+	medium
+	high
+}
+
+@[minify]
+struct Task {
+	status   Status
+	priority ?Priority
+	done     bool
+	optional ?bool
+}
+
+fn main() {
+	task := Task{
+		status: .active
+	}
+	println(task.status)
+	println(task.priority or { Priority.low })
+	println(task.done)
+	println(task.optional or { false })
+}