From b2e79dbebd5a46c12a4b0b5b224547c002925681 Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Sun, 23 Aug 2020 05:42:25 +0530
Subject: [PATCH] parser: add an error for `import mod.sub as mod` and `import
 mod as mod` (#6194)

---
 examples/net_raw_http.v                            | 2 +-
 vlib/math/stats/stats_test.v                       | 2 +-
 vlib/v/checker/tests/import_mod_as_mod_err.out     | 5 +++++
 vlib/v/checker/tests/import_mod_as_mod_err.vv      | 5 +++++
 vlib/v/checker/tests/import_mod_sub_as_sub_err.out | 5 +++++
 vlib/v/checker/tests/import_mod_sub_as_sub_err.vv  | 5 +++++
 vlib/v/parser/parser.v                             | 3 +++
 vlib/x/net/udp_test.v                              | 2 +-
 8 files changed, 26 insertions(+), 3 deletions(-)
 create mode 100644 vlib/v/checker/tests/import_mod_as_mod_err.out
 create mode 100644 vlib/v/checker/tests/import_mod_as_mod_err.vv
 create mode 100644 vlib/v/checker/tests/import_mod_sub_as_sub_err.out
 create mode 100644 vlib/v/checker/tests/import_mod_sub_as_sub_err.vv

diff --git a/examples/net_raw_http.v b/examples/net_raw_http.v
index e3b4f20a2d..c03ad818bd 100644
--- a/examples/net_raw_http.v
+++ b/examples/net_raw_http.v
@@ -1,5 +1,5 @@
 // Simple raw HTTP head request
-import x.net as net
+import x.net
 import time
 
 // Make a new connection
diff --git a/vlib/math/stats/stats_test.v b/vlib/math/stats/stats_test.v
index 45ffc04b52..7b4bbbe75e 100644
--- a/vlib/math/stats/stats_test.v
+++ b/vlib/math/stats/stats_test.v
@@ -1,4 +1,4 @@
-import math.stats as stats
+import math.stats
 import math
 
 fn test_freq() {
diff --git a/vlib/v/checker/tests/import_mod_as_mod_err.out b/vlib/v/checker/tests/import_mod_as_mod_err.out
new file mode 100644
index 0000000000..1f0bb93312
--- /dev/null
+++ b/vlib/v/checker/tests/import_mod_as_mod_err.out
@@ -0,0 +1,5 @@
+vlib/v/checker/tests/import_mod_as_mod_err.v:1:16: error: import alias `math as math` is redundant
+    1 | import math as math
+      |                ~~~~
+    2 |
+    3 | fn main() {
diff --git a/vlib/v/checker/tests/import_mod_as_mod_err.vv b/vlib/v/checker/tests/import_mod_as_mod_err.vv
new file mode 100644
index 0000000000..2a125349ad
--- /dev/null
+++ b/vlib/v/checker/tests/import_mod_as_mod_err.vv
@@ -0,0 +1,5 @@
+import math as math
+
+fn main() {
+    println(math.e)
+}
diff --git a/vlib/v/checker/tests/import_mod_sub_as_sub_err.out b/vlib/v/checker/tests/import_mod_sub_as_sub_err.out
new file mode 100644
index 0000000000..6c9a63c246
--- /dev/null
+++ b/vlib/v/checker/tests/import_mod_sub_as_sub_err.out
@@ -0,0 +1,5 @@
+vlib/v/checker/tests/import_mod_sub_as_sub_err.v:1:25: error: import alias `encoding.utf8 as utf8` is redundant
+    1 | import encoding.utf8 as utf8
+      |                         ~~~~
+    2 |
+    3 | fn main() {
diff --git a/vlib/v/checker/tests/import_mod_sub_as_sub_err.vv b/vlib/v/checker/tests/import_mod_sub_as_sub_err.vv
new file mode 100644
index 0000000000..81846bfd70
--- /dev/null
+++ b/vlib/v/checker/tests/import_mod_sub_as_sub_err.vv
@@ -0,0 +1,5 @@
+import encoding.utf8 as utf8
+
+fn main() {
+    println(utf8.validate_str('añçá'))
+}
diff --git a/vlib/v/parser/parser.v b/vlib/v/parser/parser.v
index 518bc1352f..99008a78f5 100644
--- a/vlib/v/parser/parser.v
+++ b/vlib/v/parser/parser.v
@@ -1495,6 +1495,9 @@ fn (mut p Parser) import_stmt() ast.Import {
 	if p.tok.kind == .key_as {
 		p.next()
 		mod_alias = p.check_name()
+		if mod_alias == mod_name.split('.').last() {
+			p.error_with_pos('import alias `$mod_name as $mod_alias` is redundant', p.prev_tok.position())
+		}
 	}
 	node := ast.Import{
 		pos: pos
diff --git a/vlib/x/net/udp_test.v b/vlib/x/net/udp_test.v
index d47e692065..ef86475709 100644
--- a/vlib/x/net/udp_test.v
+++ b/vlib/x/net/udp_test.v
@@ -1,4 +1,4 @@
-import x.net as net
+import x.net
 import time
 
 fn echo_server(_c net.UdpConn) {