parser, checker: check invalid lambda expr (#20461)

Author: yuyi98

vlib/v/checker/errors.v

@@ -41,6 +41,16 @@ fn (mut c Checker) error(message string, pos token.Pos) {
 	c.warn_or_error(msg, pos, false)
 }
 
+fn (mut c Checker) fatal(message string, pos token.Pos) {
+	if (c.pref.translated || c.file.is_translated) && message.starts_with('mismatched types') {
+		// TODO move this
+		return
+	}
+	msg := message.replace('`Array_', '`[]')
+	c.pref.fatal_errors = true
+	c.warn_or_error(msg, pos, false)
+}
+
 fn (mut c Checker) note(message string, pos token.Pos) {
 	if c.pref.message_limit >= 0 && c.nr_notices >= c.pref.message_limit {
 		c.should_abort = true

vlib/v/checker/lambda_expr.v

@@ -7,8 +7,8 @@ pub fn (mut c Checker) lambda_expr(mut node ast.LambdaExpr, exp_typ ast.Type) as
 	if node.is_checked {
 		return node.typ
 	}
-	if exp_typ == 0 {
-		c.error('lambda expressions are allowed only in places expecting function callbacks',
+	if exp_typ in [0, ast.void_type] {
+		c.fatal('lambda expressions are allowed only in places expecting function callbacks',
 			node.pos)
 		return ast.void_type
 	}

vlib/v/checker/tests/lambda_expression_in_map.out

@@ -2,7 +2,7 @@ vlib/v/checker/tests/lambda_expression_in_map.vv:3:12: error: lambda expressions
     1 | a := [4, 5]
     2 | dump(a.map(it))
     3 | dump(a.map(|| 5))
-      |            ~~
+      |            ~~~~
     4 | dump(a.map(|x| 5 * x))
     5 | dump(a.map(|x| x))
 vlib/v/checker/tests/lambda_expression_in_map.vv:3:8: error: dump expression can not be void
@@ -16,7 +16,7 @@ vlib/v/checker/tests/lambda_expression_in_map.vv:6:12: error: lambda expressions
     4 | dump(a.map(|x| 5 * x))
     5 | dump(a.map(|x| x))
     6 | dump(a.map(|x, y| x))
-      |            ^
+      |            ~~~~~~~~
 vlib/v/checker/tests/lambda_expression_in_map.vv:6:8: error: dump expression can not be void
     4 | dump(a.map(|x| 5 * x))
     5 | dump(a.map(|x| x))

vlib/v/checker/tests/lambda_expression_invalid.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/lambda_expression_invalid.vv:3:19: error: lambda expressions are allowed only in places expecting function callbacks
+    1 | fn main() {
+    2 |     x := 5
+    3 |     f := if x == 5 { |x| x - 5 } else { |x| x }
+      |                      ~~~~~~~~~
+    4 |     println(f(x))
+    5 | }

vlib/v/checker/tests/lambda_expression_invalid.vv

@@ -0,0 +1,5 @@
+fn main() {
+	x := 5
+	f := if x == 5 { |x| x - 5 } else { |x| x }
+	println(f(x))
+}

vlib/v/checker/tests/lambda_undefined_variables_err.out

@@ -1,33 +1,33 @@
 vlib/v/checker/tests/lambda_undefined_variables_err.vv:7:2: warning: unused variable: `s2`
     5 |     f(|x| s1)
-    6 | 
+    6 |
     7 |     s2 := 'abc'
       |     ~~
     8 |     f(|x| s2)
     9 | }
 vlib/v/checker/tests/lambda_undefined_variables_err.vv:5:8: error: undefined ident: `s1`
-    3 | 
+    3 |
     4 | fn main() {
     5 |     f(|x| s1)
       |           ~~
-    6 | 
+    6 |
     7 |     s2 := 'abc'
 vlib/v/checker/tests/lambda_undefined_variables_err.vv:5:4: error: `s1` used as value
-    3 | 
+    3 |
     4 | fn main() {
     5 |     f(|x| s1)
-      |       ^
-    6 | 
+      |       ~~~~~~
+    6 |
     7 |     s2 := 'abc'
 vlib/v/checker/tests/lambda_undefined_variables_err.vv:8:8: error: undefined variable `s2`
-    6 | 
+    6 |
     7 |     s2 := 'abc'
     8 |     f(|x| s2)
       |           ~~
     9 | }
 vlib/v/checker/tests/lambda_undefined_variables_err.vv:8:4: error: `s2` used as value
-    6 | 
+    6 |
     7 |     s2 := 'abc'
     8 |     f(|x| s2)
-      |       ^
+      |       ~~~~~~
     9 | }

vlib/v/parser/expr.v

@@ -900,7 +900,7 @@ fn (mut p Parser) lambda_expr() ?ast.LambdaExpr {
 	e := p.expr(0)
 	pos_end := p.tok.pos()
 	return ast.LambdaExpr{
-		pos: pos
+		pos: pos.extend(e.pos())
 		pos_expr: pos_expr
 		pos_end: pos_end
 		params: params