From a68d03ac599460401c635b173477a16098de7d43 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@vlang.io>
Date: Thu, 21 Jul 2022 20:56:24 +0300
Subject: [PATCH] checker: allow `x := unsafe { nil }`

---
 vlib/strings/builder.c.v     |  4 ++--
 vlib/term/ui/input.v         | 10 +++++-----
 vlib/v/ast/types.v           |  2 +-
 vlib/v/checker/assign.v      |  3 ++-
 vlib/v/checker/tests/nil.out |  2 +-
 5 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/vlib/strings/builder.c.v b/vlib/strings/builder.c.v
index dcdc5e2957..34c3afdfc4 100644
--- a/vlib/strings/builder.c.v
+++ b/vlib/strings/builder.c.v
@@ -191,7 +191,7 @@ pub fn (mut b Builder) ensure_cap(n int) {
 	}
 
 	new_data := vcalloc(n * b.element_size)
-	if b.data != voidptr(0) {
+	if b.data != unsafe { nil } {
 		unsafe { vmemcpy(new_data, b.data, b.len * b.element_size) }
 		// TODO: the old data may be leaked when no GC is used (ref-counting?)
 		if b.flags.has(.noslices) {
@@ -212,7 +212,7 @@ pub fn (mut b Builder) free() {
 	if b.data != 0 {
 		unsafe { free(b.data) }
 		unsafe {
-			b.data = voidptr(0)
+			b.data = nil
 		}
 	}
 }
diff --git a/vlib/term/ui/input.v b/vlib/term/ui/input.v
index 81b887f837..6041f10070 100644
--- a/vlib/term/ui/input.v
+++ b/vlib/term/ui/input.v
@@ -206,35 +206,35 @@ pub struct Config {
 
 [inline]
 fn (ctx &Context) init() {
-	if ctx.cfg.init_fn != voidptr(0) {
+	if ctx.cfg.init_fn != unsafe { nil } {
 		ctx.cfg.init_fn(ctx.cfg.user_data)
 	}
 }
 
 [inline]
 fn (ctx &Context) frame() {
-	if ctx.cfg.frame_fn != voidptr(0) {
+	if ctx.cfg.frame_fn != unsafe { nil } {
 		ctx.cfg.frame_fn(ctx.cfg.user_data)
 	}
 }
 
 [inline]
 fn (ctx &Context) cleanup() {
-	if ctx.cfg.cleanup_fn != voidptr(0) {
+	if ctx.cfg.cleanup_fn != unsafe { nil } {
 		ctx.cfg.cleanup_fn(ctx.cfg.user_data)
 	}
 }
 
 [inline]
 fn (ctx &Context) fail(error string) {
-	if ctx.cfg.fail_fn != voidptr(0) {
+	if ctx.cfg.fail_fn != unsafe { nil } {
 		ctx.cfg.fail_fn(error)
 	}
 }
 
 [inline]
 fn (ctx &Context) event(event &Event) {
-	if ctx.cfg.event_fn != voidptr(0) {
+	if ctx.cfg.event_fn != unsafe { nil } {
 		ctx.cfg.event_fn(event, ctx.cfg.user_data)
 	}
 }
diff --git a/vlib/v/ast/types.v b/vlib/v/ast/types.v
index 944738318d..dedf336e27 100644
--- a/vlib/v/ast/types.v
+++ b/vlib/v/ast/types.v
@@ -812,7 +812,7 @@ pub fn (mut t Table) register_builtin_type_symbols() {
 		}
 	)
 	t.register_sym(kind: .interface_, name: 'IError', cname: 'IError', mod: 'builtin')
-	t.register_sym(kind: .voidptr, name: 'nil', cname: 'nil', mod: 'builtin')
+	t.register_sym(kind: .voidptr, name: 'nil', cname: 'voidptr', mod: 'builtin')
 }
 
 [inline]
diff --git a/vlib/v/checker/assign.v b/vlib/v/checker/assign.v
index 0df46b0cff..75d3d3d157 100644
--- a/vlib/v/checker/assign.v
+++ b/vlib/v/checker/assign.v
@@ -222,7 +222,8 @@ pub fn (mut c Checker) assign_stmt(mut node ast.AssignStmt) {
 						}
 						if right is ast.Nil {
 							// `x := unsafe { nil }` is allowed
-							c.error('use of untyped nil in assignment', right.pos())
+							c.error('use of untyped nil in assignment (use `unsafe`)',
+								right.pos())
 						}
 					}
 					mut ident_var_info := left.info as ast.IdentVar
diff --git a/vlib/v/checker/tests/nil.out b/vlib/v/checker/tests/nil.out
index 6d4d981d28..74f4da2ba4 100644
--- a/vlib/v/checker/tests/nil.out
+++ b/vlib/v/checker/tests/nil.out
@@ -1,4 +1,4 @@
-vlib/v/checker/tests/nil.vv:3:18: error: use of untyped nil in assignment
+vlib/v/checker/tests/nil.vv:3:18: error: use of untyped nil in assignment (use `unsafe`)
     1 | fn main() {
     2 |     unsafe {
     3 |         value := nil