semver: add custom errors (#9493)

examples/errors.v

@@ -0,0 +1,20 @@
+import semver
+
+fn main() {
+	semver.from('asd') or { check_error(err) }
+	semver.from('') or { check_error(err) }
+}
+
+fn check_error(err IError) {
+	match err {
+		semver.InvalidVersionFormatError {
+			println('wrong format')
+		}
+		semver.EmptyInputError {
+			println('empty input')
+		}
+		else {
+			println('unknown error')
+		}
+	}
+}

vlib/semver/range.v

@@ -29,6 +29,16 @@ struct Range {
 	comparator_sets []ComparatorSet
 }
 
+struct InvalidComparatorCountError {
+	msg  string
+	code int
+}
+
+struct InvalidComparatorFormatError {
+	msg  string
+	code int
+}
+
 fn (r Range) satisfies(ver Version) bool {
 	mut final_result := false
 	for set in r.comparator_sets {
@@ -74,12 +84,16 @@ fn parse_range(input string) ?Range {
 fn parse_comparator_set(input string) ?ComparatorSet {
 	raw_comparators := input.split(semver.comparator_sep)
 	if raw_comparators.len > 2 {
-		return error('Invalid format of comparator set for input "$input"')
+		return IError(&InvalidComparatorFormatError{
+			msg: 'Invalid format of comparator set for input "$input"'
+		})
 	}
 	mut comparators := []Comparator{}
 	for raw_comp in raw_comparators {
 		c := parse_comparator(raw_comp) or {
-			return error('Invalid comparator "$raw_comp" in input "$input"')
+			return IError(&InvalidComparatorFormatError{
+				msg: 'Invalid comparator "$raw_comp" in input "$input"'
+			})
 		}
 		comparators << c
 	}

vlib/semver/semver.v

@@ -19,15 +19,27 @@ pub enum Increment {
 	patch
 }
 
+struct EmptyInputError {
+	msg  string = 'Empty input'
+	code int
+}
+
+struct InvalidVersionFormatError {
+	msg  string
+	code int
+}
+
 // * Constructor.
 // from returns a `Version` structure parsed from `input` `string`.
 pub fn from(input string) ?Version {
 	if input.len == 0 {
-		return error('Empty input')
+		return IError(&EmptyInputError{})
 	}
 	raw_version := parse(input)
 	version := raw_version.validate() or {
-		return error('Invalid version format for input "$input"')
+		return IError(&InvalidVersionFormatError{
+			msg: 'Invalid version format for input "$input"'
+		})
 	}
 	return version
 }
@@ -88,8 +100,7 @@ v := semver.coerce('1.3-RC1-b2') or { semver.Version{} }
 assert v.satisfies('>1.0 <2.0') == true // 1.3.0
 */
 pub fn coerce(input string) ?Version {
-	ver := coerce_version(input) or { return error('Invalid version for input "$input"') }
+	return coerce_version(input)
-	return ver
 }
 
 // is_valid returns `true` if the `input` `string` can be converted to