checker: support lambda expressions in array methods like `a.map(|x|x…

…*10)` too (#19424)

vlib/builtin/lambda_expr_array_test.v

@@ -0,0 +1,35 @@
+const a = [4, 5, 1, 2, 5, 9]
+
+fn test_map() {
+	assert a.map(it) == a
+	assert a.map(it * 10) == [40, 50, 10, 20, 50, 90]
+	//
+	assert a.map(|x| x) == a
+	assert a.map(|x| x * 10) == [40, 50, 10, 20, 50, 90]
+	assert a.map(|x| 'x: ${x}') == ['x: 4', 'x: 5', 'x: 1', 'x: 2', 'x: 5', 'x: 9']
+	assert a.map(|x| f64(x) * 10.0) == [40.0, 50.0, 10.0, 20.0, 50.0, 90.0]
+}
+
+fn test_filter() {
+	assert a.filter(it > 4) == [5, 5, 9]
+	assert a.filter(it < 4) == [1, 2]
+	//
+	assert a.filter(|x| x > 4) == [5, 5, 9]
+	assert a.filter(|x| x < 4) == [1, 2]
+}
+
+fn test_any() {
+	assert a.any(it > 4)
+	assert !a.any(it > 40)
+
+	assert a.any(|x| x > 4)
+	assert !a.any(|x| x > 40)
+}
+
+fn test_all() {
+	assert !a.all(it > 4)
+	assert a.all(it < 40)
+
+	assert !a.all(|x| x > 4)
+	assert a.all(|x| x < 40)
+}

vlib/v/ast/ast.v

@@ -1786,9 +1786,9 @@ pub:
 
 pub struct LambdaExpr {
 pub:
-	pos    token.Pos
-	params []Ident
+	pos token.Pos
 pub mut:
+	params     []Ident
 	pos_expr   token.Pos
 	expr       Expr
 	pos_end    token.Pos

vlib/v/checker/fn.v

@@ -2587,6 +2587,7 @@ fn (mut c Checker) array_builtin_method_call(mut node ast.CallExpr, left_type as
 	mut elem_typ := ast.void_type
 	if method_name == 'slice' && !c.is_builtin_mod {
 		c.error('.slice() is a private method, use `x[start..end]` instead', node.pos)
+		return ast.void_type
 	}
 	array_info := if left_sym.info is ast.Array {
 		left_sym.info as ast.Array
@@ -2595,10 +2596,27 @@ fn (mut c Checker) array_builtin_method_call(mut node ast.CallExpr, left_type as
 	}
 	elem_typ = array_info.elem_type
 	if method_name in ['filter', 'map', 'any', 'all'] {
-		// position of `it` doesn't matter
-		scope_register_it(mut node.scope, node.pos, elem_typ)
+		if node.args.len > 0 && mut node.args[0].expr is ast.LambdaExpr {
+			if node.args[0].expr.params.len != 1 {
+				c.error('lambda expressions used in the builtin array methods require exactly 1 parameter',
+					node.args[0].expr.pos)
+				return ast.void_type
+			}
+			if method_name == 'map' {
+				c.lambda_expr_fix_type_of_param(mut node.args[0].expr, mut node.args[0].expr.params[0],
+					elem_typ)
+				le_type := c.expr(mut node.args[0].expr.expr)
+				// eprintln('>>>>> node.args[0].expr: ${ast.Expr(node.args[0].expr)} | elem_typ: ${elem_typ} | etype: ${le_type}')
+				c.support_lambda_expr_one_param(elem_typ, le_type, mut node.args[0].expr)
+			} else {
+				c.support_lambda_expr_one_param(elem_typ, ast.bool_type, mut node.args[0].expr)
+			}
+		} else {
+			// position of `it` doesn't matter
+			scope_register_it(mut node.scope, node.pos, elem_typ)
+		}
 	} else if method_name == 'sorted_with_compare' && node.args.len == 1 {
-		if mut node.args[0].expr is ast.LambdaExpr {
+		if node.args.len > 0 && mut node.args[0].expr is ast.LambdaExpr {
 			c.support_lambda_expr_in_sort(elem_typ.ref(), ast.int_type, mut node.args[0].expr)
 		}
 	} else if method_name == 'sort' || method_name == 'sorted' {
@@ -2671,6 +2689,7 @@ fn (mut c Checker) array_builtin_method_call(mut node ast.CallExpr, left_type as
 		arg_type = c.check_expr_opt_call(arg.expr, c.expr(mut arg.expr))
 	}
 	if method_name == 'map' {
+		// eprintln('>>>>>>> map node.args[0].expr: ${node.args[0].expr}, left_type: ${left_type} | elem_typ: ${elem_typ} | arg_type: ${arg_type}')
 		// check fn
 		c.check_map_and_filter(true, elem_typ, node)
 		arg_sym := c.table.sym(arg_type)
@@ -2777,25 +2796,19 @@ fn (mut c Checker) array_builtin_method_call(mut node ast.CallExpr, left_type as
 }
 
 fn scope_register_it(mut s ast.Scope, pos token.Pos, typ ast.Type) {
-	s.register(ast.Var{
-		name: 'it'
-		pos: pos
-		typ: typ
-		is_used: true
-	})
+	scope_register_var_name(mut s, pos, typ, 'it')
 }
 
 fn scope_register_a_b(mut s ast.Scope, pos token.Pos, typ ast.Type) {
+	scope_register_var_name(mut s, pos, typ.ref(), 'a')
+	scope_register_var_name(mut s, pos, typ.ref(), 'b')
+}
+
+fn scope_register_var_name(mut s ast.Scope, pos token.Pos, typ ast.Type, name string) {
 	s.register(ast.Var{
-		name: 'a'
-		pos: pos
-		typ: typ.ref()
-		is_used: true
-	})
-	s.register(ast.Var{
-		name: 'b'
+		name: name
 		pos: pos
-		typ: typ.ref()
+		typ: typ
 		is_used: true
 	})
 }

vlib/v/checker/lambda_expr.v

@@ -33,17 +33,7 @@ pub fn (mut c Checker) lambda_expr(mut node ast.LambdaExpr, exp_typ ast.Type) as
 			eparam := exp_sym.info.func.params[idx]
 			eparam_type := eparam.typ
 			eparam_auto_deref := eparam.typ.is_ptr()
-			if mut v := node.scope.find(x.name) {
-				if mut v is ast.Var {
-					v.is_arg = true
-					v.typ = eparam_type
-					v.expr = ast.empty_expr
-					v.is_auto_deref = eparam_auto_deref
-				}
-			}
-			c.ident(mut x)
-			x.obj.typ = eparam_type
-
+			c.lambda_expr_fix_type_of_param(mut node, mut x, eparam_type)
 			params << ast.Param{
 				pos: x.pos
 				name: x.name
@@ -100,6 +90,19 @@ pub fn (mut c Checker) lambda_expr(mut node ast.LambdaExpr, exp_typ ast.Type) as
 	return exp_typ
 }
 
+pub fn (mut c Checker) lambda_expr_fix_type_of_param(mut node ast.LambdaExpr, mut pident ast.Ident, ptype ast.Type) {
+	if mut v := node.scope.find(pident.name) {
+		if mut v is ast.Var {
+			v.is_arg = true
+			v.typ = ptype
+			v.is_auto_deref = ptype.is_ptr()
+			v.expr = ast.empty_expr
+		}
+	}
+	c.ident(mut pident)
+	pident.obj.typ = ptype
+}
+
 pub fn (mut c Checker) support_lambda_expr_in_sort(param_type ast.Type, return_type ast.Type, mut expr ast.LambdaExpr) {
 	is_auto_rec := param_type.is_ptr()
 	mut expected_fn := ast.Fn{
@@ -121,3 +124,19 @@ pub fn (mut c Checker) support_lambda_expr_in_sort(param_type ast.Type, return_t
 		false))
 	c.lambda_expr(mut expr, expected_fn_type)
 }
+
+pub fn (mut c Checker) support_lambda_expr_one_param(param_type ast.Type, return_type ast.Type, mut expr ast.LambdaExpr) {
+	mut expected_fn := ast.Fn{
+		params: [
+			ast.Param{
+				name: 'xx'
+				typ: param_type
+				is_auto_rec: param_type.is_ptr()
+			},
+		]
+		return_type: return_type
+	}
+	cb_type := c.table.find_or_register_fn_type(expected_fn, true, false)
+	expected_fn_type := ast.new_type(cb_type)
+	c.lambda_expr(mut expr, expected_fn_type)
+}

vlib/v/checker/tests/lambda_expression_in_map.out

@@ -0,0 +1,12 @@
+vlib/v/checker/tests/lambda_expression_in_map.vv:3:12: error: lambda expressions used in the builtin array methods require exactly 1 parameter
+    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:6:12: error: lambda expressions used in the builtin array methods require exactly 1 parameter
+    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

@@ -0,0 +1,6 @@
+a := [4, 5]
+dump(a.map(it))
+dump(a.map(|| 5))
+dump(a.map(|x| 5 * x))
+dump(a.map(|x| x))
+dump(a.map(|x, y| x))