From e03ece2a4b0eb3c1400c2ad813f4c7d5b22e4b66 Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Sat, 30 Jan 2021 02:41:05 +0530
Subject: [PATCH] checker: check the fn decl for anon fns too (#7529)

---
 vlib/net/udp.v                  | 13 +++++++------
 vlib/v/ast/ast.v                |  5 ++---
 vlib/v/checker/checker.v        | 10 +++++++++-
 vlib/v/checker/tests/fn_var.out |  5 +++++
 4 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/vlib/net/udp.v b/vlib/net/udp.v
index e69cf39ab1..7d769c5e77 100644
--- a/vlib/net/udp.v
+++ b/vlib/net/udp.v
@@ -18,12 +18,6 @@ mut:
 }
 
 pub fn dial_udp(laddr string, raddr string) ?&UdpConn {
-	// Dont have to do this when its fixed
-	// this just allows us to store this `none` optional in a struct
-	resolve_wrapper := fn (raddr string) ?Addr {
-		x := resolve_addr(raddr, .inet, .udp) or { return none }
-		return x
-	}
 	local := resolve_addr(laddr, .inet, .udp) ?
 	sbase := new_udp_socket(local.port) ?
 	sock := UdpSocket{
@@ -38,6 +32,13 @@ pub fn dial_udp(laddr string, raddr string) ?&UdpConn {
 	}
 }
 
+fn resolve_wrapper(raddr string) ?Addr {
+	// Dont have to do this when its fixed
+	// this just allows us to store this `none` optional in a struct
+	x := resolve_addr(raddr, .inet, .udp) or { return none }
+	return x
+}
+
 pub fn (mut c UdpConn) write_ptr(b byteptr, len int) ? {
 	remote := c.sock.remote() or { return err_no_udp_remote }
 	return c.write_to_ptr(remote, b, len)
diff --git a/vlib/v/ast/ast.v b/vlib/v/ast/ast.v
index 3cf5ada5d8..8f6a82da08 100644
--- a/vlib/v/ast/ast.v
+++ b/vlib/v/ast/ast.v
@@ -295,10 +295,9 @@ pub:
 
 // anonymous function
 pub struct AnonFn {
-pub:
-	decl FnDecl
 pub mut:
-	typ table.Type // the type of anonymous fn. Both .typ and .decl.name are auto generated
+	decl FnDecl
+	typ  table.Type // the type of anonymous fn. Both .typ and .decl.name are auto generated
 }
 
 // function or method declaration
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index b4cdb91126..43fa4a0886 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -59,6 +59,7 @@ pub mut:
 	is_builtin_mod    bool   // are we in `builtin`?
 	inside_unsafe     bool
 	inside_const      bool
+	inside_anon_fn    bool
 	skip_flags        bool // should `#flag` and `#include` be skipped
 	cur_generic_types []table.Type
 mut:
@@ -3283,10 +3284,13 @@ pub fn (mut c Checker) expr(node ast.Expr) table.Type {
 			return node.typ
 		}
 		ast.AnonFn {
+			c.inside_anon_fn = true
 			keep_fn := c.cur_fn
 			c.cur_fn = &node.decl
 			c.stmts(node.decl.stmts)
+			c.fn_decl(mut node.decl)
 			c.cur_fn = keep_fn
+			c.inside_anon_fn = false
 			return node.typ
 		}
 		ast.ArrayDecompose {
@@ -5400,7 +5404,11 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
 	returns := c.returns || has_top_return(node.stmts)
 	if node.language == .v && !node.no_body && node.return_type != table.void_type && !returns
 		&& node.name !in ['panic', 'exit'] {
-		c.error('missing return at end of function `$node.name`', node.pos)
+		if c.inside_anon_fn {
+			c.error('missing return at the end of an anonymous function', node.pos)
+		} else {
+			c.error('missing return at end of function `$node.name`', node.pos)
+		}
 	}
 	c.returns = false
 	node.source_file = c.file
diff --git a/vlib/v/checker/tests/fn_var.out b/vlib/v/checker/tests/fn_var.out
index ace817b996..d1db2a0f07 100644
--- a/vlib/v/checker/tests/fn_var.out
+++ b/vlib/v/checker/tests/fn_var.out
@@ -1,3 +1,8 @@
+vlib/v/checker/tests/fn_var.vv:1:10: error: missing return at the end of an anonymous function
+    1 | mut f := fn(i int) byte {}
+      |          ~~~~~~~~~~~~~~~~~
+    2 | f = 4
+    3 | mut p := &f
 vlib/v/checker/tests/fn_var.vv:2:5: error: cannot assign to `f`: expected `fn (int) byte`, not `int literal`
     1 | mut f := fn(i int) byte {}
     2 | f = 4