compiler: handle ranges as `match` conditions (#5847)

vlib/v/checker/checker.v

@@ -2585,6 +2585,39 @@ fn (mut c Checker) match_exprs(mut node ast.MatchExpr, type_sym table.TypeSymbol
 	for branch in node.branches {
 		for expr in branch.exprs {
 			mut key := ''
+			if expr is ast.RangeExpr {
+				mut low := 0
+				mut high := 0
+				c.expected_type = node.expected_type
+				if expr.low is ast.IntegerLiteral as low_expr {
+					if expr.high is ast.IntegerLiteral as high_expr {
+						low = low_expr.val.int()
+						high = high_expr.val.int()
+					} else {
+						c.error('mismatched range types', low_expr.pos)
+					}
+				} else if expr.low is ast.CharLiteral as low_expr {
+					if expr.high is ast.CharLiteral as high_expr {
+						low = low_expr.val[0]
+						high = high_expr.val[0]
+					} else {
+						c.error('mismatched range types', low_expr.pos)
+					}
+				} else {
+					typ := c.table.type_to_str(c.expr(expr.low))
+					c.error('cannot use type `$typ` in match range', branch.pos)
+				}
+
+				for i in low..high {
+					key = i.str()
+					val := if key in branch_exprs { branch_exprs[key] } else { 0 }
+					if val == 1 {
+						c.error('match case `$key` is handled more than once', branch.pos)
+					}
+					branch_exprs[key] = val + 1
+				}
+				continue
+			}
 			match expr {
 				ast.Type { key = c.table.type_to_str(expr.typ) }
 				ast.EnumVal { key = expr.val }

vlib/v/checker/tests/match_duplicate_branch.out

@@ -33,3 +33,10 @@ vlib/v/checker/tests/match_duplicate_branch.v:43:3: error: match case `2` is han
       |         ~~~
    44 |         else { println('else') }
    45 |     }
+vlib/v/checker/tests/match_duplicate_branch.v:51:3: error: match case `3` is handled more than once
+   49 |     match i {
+   50 |         1..5 { println('1 to 4') }
+   51 |         3 { println('3') }
+      |         ~~~
+   52 |         else { println('else') }
+   53 |     }

vlib/v/checker/tests/match_duplicate_branch.vv

@@ -45,8 +45,17 @@ fn test_int(i int) {
 	}
 }
 
+fn test_range(i int) {
+	match i {
+		1..5 { println('1 to 4') }
+		3 { println('3') }
+		else { println('else') }
+	}
+}
+
 fn main() {
 	test_sum_type(St1{})
 	test_enum(.red)
 	test_int(2)
+	test_range(4)
 }

vlib/v/gen/cgen.v

@@ -2226,20 +2226,30 @@ fn (mut g Gen) match_expr(node ast.MatchExpr) {
 						// g.write('._interface_idx == _${sym.name}_${branch_sym} ')
 						g.write('._interface_idx == ')
 					}
+					g.expr(expr)
 				} else if type_sym.kind == .string {
 					g.write('string_eq(')
 					//
 					g.expr(node.cond)
 					g.write(', ')
 					// g.write('string_eq($tmp, ')
+					g.expr(expr)
+					g.write(')')
+				} else if expr is ast.RangeExpr {
+					g.write('(')
+					g.expr(node.cond)
+					g.write(' >= ')
+					g.expr(expr.low)
+					g.write(' && ')
+					g.expr(node.cond)
+					g.write(' < ')
+					g.expr(expr.high)
+					g.write(')')
 				} else {
 					g.expr(node.cond)
 					g.write(' == ')
 					// g.write('$tmp == ')
-				}
+					g.expr(expr)
-				g.expr(expr)
-				if type_sym.kind == .string {
-					g.write(')')
 				}
 				if i < branch.exprs.len - 1 {
 					g.write(' || ')

vlib/v/parser/if.v

@@ -187,7 +187,18 @@ fn (mut p Parser) match_expr() ast.MatchExpr {
 				p.inside_match_case = true
 				expr := p.expr(0)
 				p.inside_match_case = false
-				exprs << expr
+				if p.tok.kind == .dotdot {
+					p.next()
+					expr2 := p.expr(0)
+					exprs << ast.RangeExpr{
+						low: expr
+						high: expr2
+						has_low: true
+						has_high: true
+					}
+				} else {
+					exprs << expr
+				}
 				if p.tok.kind != .comma {
 					break
 				}

vlib/v/tests/match_test.v

@@ -62,6 +62,24 @@ fn test_match_integers() {
 	assert a == -2
 }
 
+fn test_match_multiple() {
+	assert match 5 {
+		1, 2, 3 { '1-3' }
+		4, 5 { '4-5' }
+		6..9, 9 { '6-9' }
+		else { 'other' }
+	} == '4-5'
+}
+
+fn test_match_range() {
+	assert match `f` {
+		`0`..`9` { 'digit' }
+		`A`..`Z` { 'uppercase' }
+		`a`..`z` { 'lowercase' }
+		else { 'other' }
+	} == 'lowercase'
+}
+
 fn test_match_enums() {
 	mut b := Color.red
 	match b {