From e7fd8c4e7c0c4c72fef6ff1d6ab5b7ae51346367 Mon Sep 17 00:00:00 2001
From: yuyi <yuyi98@163.com>
Date: Thu, 7 Apr 2022 17:01:54 +0800
Subject: [PATCH] cgen: fix error for dereference mut interface in loop (fix
 #13913) (#13941)

---
 vlib/v/gen/c/fn.v                              | 18 ++++++++++++++++--
 ...> dereference_mut_interface_in_loop_test.v} |  4 ++--
 vlib/v/tests/known_errors/testdata/README.md   |  8 ++++++++
 3 files changed, 26 insertions(+), 4 deletions(-)
 rename vlib/v/tests/{known_errors/testdata/dereference_mut_interface_in_loop.vv => dereference_mut_interface_in_loop_test.v} (82%)
 create mode 100644 vlib/v/tests/known_errors/testdata/README.md

diff --git a/vlib/v/gen/c/fn.v b/vlib/v/gen/c/fn.v
index 876cb53eb1..3bbd65a198 100644
--- a/vlib/v/gen/c/fn.v
+++ b/vlib/v/gen/c/fn.v
@@ -775,7 +775,14 @@ fn (mut g Gen) method_call(node ast.CallExpr) {
 		left_cc_type := g.cc_type(node.left_type, false)
 		left_type_name := util.no_dots(left_cc_type)
 		g.write('${c_name(left_type_name)}_name_table[')
-		g.expr(node.left)
+		if node.left.is_auto_deref_var() && node.left_type.nr_muls() > 1 {
+			g.write('(')
+			g.write('*'.repeat(node.left_type.nr_muls() - 1))
+			g.expr(node.left)
+			g.write(')')
+		} else {
+			g.expr(node.left)
+		}
 		dot := if left_is_shared {
 			'->val.'
 		} else if node.left_type.is_ptr() {
@@ -785,7 +792,14 @@ fn (mut g Gen) method_call(node ast.CallExpr) {
 		}
 		mname := c_name(node.name)
 		g.write('${dot}_typ]._method_${mname}(')
-		g.expr(node.left)
+		if node.left.is_auto_deref_var() && node.left_type.nr_muls() > 1 {
+			g.write('(')
+			g.write('*'.repeat(node.left_type.nr_muls() - 1))
+			g.expr(node.left)
+			g.write(')')
+		} else {
+			g.expr(node.left)
+		}
 		g.write('${dot}_object')
 		if node.args.len > 0 {
 			g.write(', ')
diff --git a/vlib/v/tests/known_errors/testdata/dereference_mut_interface_in_loop.vv b/vlib/v/tests/dereference_mut_interface_in_loop_test.v
similarity index 82%
rename from vlib/v/tests/known_errors/testdata/dereference_mut_interface_in_loop.vv
rename to vlib/v/tests/dereference_mut_interface_in_loop_test.v
index 223181211d..c8b53b1855 100644
--- a/vlib/v/tests/known_errors/testdata/dereference_mut_interface_in_loop.vv
+++ b/vlib/v/tests/dereference_mut_interface_in_loop_test.v
@@ -4,15 +4,15 @@ import rand
 import rand.wyrand
 import rand.splitmix64
 
-fn main() {
+fn test_deref_mut_interface_in_loop() {
 	mut wyrand_rng := &rand.PRNG(&wyrand.WyRandRNG{})
 	mut splitmix_rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
 
 	mut generators := [wyrand_rng, splitmix_rng]
 	for mut rng in generators {
 		seed_len := rng.block_size() / 32
-		// NB: `seed_len := (*rng).block_size() / 32` does compile
 		dump(seed_len)
 		println(rng.string(15))
+		assert seed_len == 2
 	}
 }
diff --git a/vlib/v/tests/known_errors/testdata/README.md b/vlib/v/tests/known_errors/testdata/README.md
new file mode 100644
index 0000000000..595b5dcc08
--- /dev/null
+++ b/vlib/v/tests/known_errors/testdata/README.md
@@ -0,0 +1,8 @@
+## Run the tests here with: `v vlib/v/tests/known_errors/known_errors_test.v`
+
+The intended use of this, is for providing samples, that currently do NOT compile,
+but that a future compiler improvement WILL be able to compile, and to track,
+whether they were not fixed incidentally, due to an unrelated change/improvement.
+For example, code that triggers generating invalid C code can go here,
+and later when a bug is fixed, can be moved to a proper _test.v or .vv/.out pair, 
+outside of the vlib/v/tests/known_errors/testdata/ folder.