From 8ab0d42b5ffa903085db0fd60f2ad1877e64013a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Uwe=20Kr=C3=BCger?=
 <45282134+UweKrueger@users.noreply.github.com>
Date: Mon, 19 Apr 2021 10:41:21 +0200
Subject: [PATCH] checker: check argument for `chan.try_push/pop()` (#9798)

---
 doc/docs.md                        |  2 +-
 vlib/sync/channel_polling_test.v   |  2 +-
 vlib/sync/channel_try_buf_test.v   |  2 +-
 vlib/sync/channel_try_unbuf_test.v |  2 +-
 vlib/v/checker/checker.v           | 39 ++++++++++++++++++++++++------
 vlib/v/checker/tests/chan_args.out | 28 +++++++++++++++++++++
 vlib/v/checker/tests/chan_args.vv  | 15 ++++++++++++
 7 files changed, 78 insertions(+), 12 deletions(-)
 create mode 100644 vlib/v/checker/tests/chan_args.out
 create mode 100644 vlib/v/checker/tests/chan_args.vv

diff --git a/doc/docs.md b/doc/docs.md
index 3daa934acd..f3417d2aec 100644
--- a/doc/docs.md
+++ b/doc/docs.md
@@ -2904,7 +2904,7 @@ println(l)
 println(c)
 mut b := Abc{}
 ch2 := chan Abc{}
-res2 := ch2.try_pop(b) // try to perform `b = <-ch2`
+res2 := ch2.try_pop(mut b) // try to perform `b = <-ch2`
 ```
 
 The `try_push/pop()` methods will return immediately with one of the results
diff --git a/vlib/sync/channel_polling_test.v b/vlib/sync/channel_polling_test.v
index ba8e1d5c03..f1a7329c7c 100644
--- a/vlib/sync/channel_polling_test.v
+++ b/vlib/sync/channel_polling_test.v
@@ -18,7 +18,7 @@ fn do_rec(ch chan int, resch chan i64, n int) {
 	mut sum := i64(0)
 	for _ in 0 .. n {
 		mut r := 0
-		for ch.try_pop(r) != .success {
+		for ch.try_pop(mut r) != .success {
 		}
 		sum += r
 	}
diff --git a/vlib/sync/channel_try_buf_test.v b/vlib/sync/channel_try_buf_test.v
index 6a0a88dfa3..0d718386aa 100644
--- a/vlib/sync/channel_try_buf_test.v
+++ b/vlib/sync/channel_try_buf_test.v
@@ -7,7 +7,7 @@ fn test_channel_try_buffered() {
 		}
 	}
 	mut obj := int(0)
-	for ch.try_pop(obj) == .success {
+	for ch.try_pop(mut obj) == .success {
 		println(obj)
 	}
 	assert obj == 6
diff --git a/vlib/sync/channel_try_unbuf_test.v b/vlib/sync/channel_try_unbuf_test.v
index 45dbe33443..9b710f20fc 100644
--- a/vlib/sync/channel_try_unbuf_test.v
+++ b/vlib/sync/channel_try_unbuf_test.v
@@ -8,6 +8,6 @@ fn test_channel_try_unbuffered() {
 		panic('push on non-ready channel not detected')
 	}
 	mut obj := -17
-	for ch.try_pop(obj) == .success {}
+	for ch.try_pop(mut obj) == .success {}
 	assert obj == -17
 }
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index e584f21712..6f3da5837f 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1612,22 +1612,44 @@ pub fn (mut c Checker) method_call(mut call_expr ast.CallExpr) ast.Type {
 		} else {
 			call_expr.return_type = method.return_type
 		}
-
+		mut exp_arg_typ := ast.Type(0) // type of 1st arg for special builtin methods
+		mut param_is_mut := false
+		mut no_type_promotion := false
+		if left_type_sym.kind == .chan {
+			elem_typ := (left_type_sym.info as ast.Chan).elem_type
+			if method_name == 'try_push' {
+				exp_arg_typ = elem_typ.to_ptr()
+			} else if method_name == 'try_pop' {
+				exp_arg_typ = elem_typ
+				param_is_mut = true
+				no_type_promotion = true
+			}
+		}
 		// if method_name == 'clone' {
 		// println('CLONE nr args=$method.args.len')
 		// }
 		// call_expr.args << method.args[0].typ
 		// call_expr.exp_arg_types << method.args[0].typ
 		for i, arg in call_expr.args {
-			exp_arg_typ := if method.is_variadic && i >= method.params.len - 1 {
-				method.params[method.params.len - 1].typ
-			} else {
-				method.params[i + 1].typ
+			if i > 0 || exp_arg_typ == ast.Type(0) {
+				exp_arg_typ = if method.is_variadic && i >= method.params.len - 1 {
+					method.params[method.params.len - 1].typ
+				} else {
+					method.params[i + 1].typ
+				}
+				param_is_mut = false
+				no_type_promotion = false
 			}
 			exp_arg_sym := c.table.get_type_symbol(exp_arg_typ)
 			c.expected_type = exp_arg_typ
 			got_arg_typ := c.check_expr_opt_call(arg.expr, c.expr(arg.expr))
 			call_expr.args[i].typ = got_arg_typ
+			if no_type_promotion {
+				if got_arg_typ != exp_arg_typ {
+					c.error('cannot use `${c.table.get_type_symbol(got_arg_typ).name}` as argument for `$method.name` (`$exp_arg_sym.name` expected)',
+						arg.pos)
+				}
+			}
 			if method.is_variadic && got_arg_typ.has_flag(.variadic) && call_expr.args.len - 1 > i {
 				c.error('when forwarding a variadic variable, it must be the final argument',
 					arg.pos)
@@ -1656,6 +1678,7 @@ pub fn (mut c Checker) method_call(mut call_expr ast.CallExpr) ast.Type {
 			} else {
 				method.params[i + 1]
 			}
+			param_is_mut = param_is_mut || param.is_mut
 			param_share := param.typ.share()
 			if param_share == .shared_t && (c.locked_names.len > 0 || c.rlocked_names.len > 0) {
 				c.error('method with `shared` arguments cannot be called inside `lock`/`rlock` block',
@@ -1663,12 +1686,12 @@ pub fn (mut c Checker) method_call(mut call_expr ast.CallExpr) ast.Type {
 			}
 			if arg.is_mut {
 				to_lock, pos := c.fail_if_immutable(arg.expr)
-				if !param.is_mut {
+				if !param_is_mut {
 					tok := arg.share.str()
 					c.error('`$call_expr.name` parameter `$param.name` is not `$tok`, `$tok` is not needed`',
 						arg.expr.position())
 				} else {
-					if param.typ.share() != arg.share {
+					if param_share != arg.share {
 						c.error('wrong shared type', arg.expr.position())
 					}
 					if to_lock != '' && param_share != .shared_t {
@@ -1677,7 +1700,7 @@ pub fn (mut c Checker) method_call(mut call_expr ast.CallExpr) ast.Type {
 					}
 				}
 			} else {
-				if param.is_mut {
+				if param_is_mut {
 					tok := arg.share.str()
 					c.error('`$call_expr.name` parameter `$param.name` is `$tok`, you need to provide `$tok` e.g. `$tok arg${
 						i + 1}`', arg.expr.position())
diff --git a/vlib/v/checker/tests/chan_args.out b/vlib/v/checker/tests/chan_args.out
new file mode 100644
index 0000000000..605bcfe790
--- /dev/null
+++ b/vlib/v/checker/tests/chan_args.out
@@ -0,0 +1,28 @@
+vlib/v/checker/tests/chan_args.vv:4:19: error: cannot use `int` as `&f64` in argument 1 to `chan f64.try_push`
+    2 |     ch := chan f64{cap: 5}
+    3 |     a := 2
+    4 |     _ := ch.try_push(a)
+      |                      ^
+    5 |     _ := ch.try_push(2.5)
+    6 |     b := 2.5
+vlib/v/checker/tests/chan_args.vv:5:19: error: cannot use `float literal` as `&f64` in argument 1 to `chan f64.try_push`
+    3 |     a := 2
+    4 |     _ := ch.try_push(a)
+    5 |     _ := ch.try_push(2.5)
+      |                      ~~~
+    6 |     b := 2.5
+    7 |     _ := ch.try_pop(b)
+vlib/v/checker/tests/chan_args.vv:7:18: error: `try_pop` parameter `obj` is `mut`, you need to provide `mut` e.g. `mut arg1`
+    5 |     _ := ch.try_push(2.5)
+    6 |     b := 2.5
+    7 |     _ := ch.try_pop(b)
+      |                     ^
+    8 |     // this should work:
+    9 |     _ := ch.try_push(b)
+vlib/v/checker/tests/chan_args.vv:11:22: error: cannot use `int` as argument for `try_pop` (`f64` expected)
+    9 |     _ := ch.try_push(b)
+   10 |     mut c := 7
+   11 |     _ := ch.try_pop(mut c)
+      |                         ^
+   12 |     mut x := 12.5
+   13 |     // this should work:
diff --git a/vlib/v/checker/tests/chan_args.vv b/vlib/v/checker/tests/chan_args.vv
new file mode 100644
index 0000000000..ce16cd8afe
--- /dev/null
+++ b/vlib/v/checker/tests/chan_args.vv
@@ -0,0 +1,15 @@
+fn main() {
+	ch := chan f64{cap: 5}
+	a := 2
+	_ := ch.try_push(a)
+	_ := ch.try_push(2.5)
+	b := 2.5
+	_ := ch.try_pop(b)
+	// this should work:
+	_ := ch.try_push(b)
+	mut c := 7
+	_ := ch.try_pop(mut c)
+	mut x := 12.5
+	// this should work:
+	_ := ch.try_pop(mut x)
+}