From a57e01fee7a097301f390cfa8b46bb84bf7e3891 Mon Sep 17 00:00:00 2001
From: Henrixounez <30901439+Henrixounez@users.noreply.github.com>
Date: Thu, 1 Oct 2020 22:29:49 +0200
Subject: [PATCH] parser: dont allow single letter enums (#6526)

---
 vlib/v/checker/tests/enum_single_letter.out | 5 +++++
 vlib/v/checker/tests/enum_single_letter.vv  | 4 ++++
 vlib/v/parser/parse_type.v                  | 2 +-
 vlib/v/parser/parser.v                      | 4 ++++
 4 files changed, 14 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/checker/tests/enum_single_letter.out
 create mode 100644 vlib/v/checker/tests/enum_single_letter.vv

diff --git a/vlib/v/checker/tests/enum_single_letter.out b/vlib/v/checker/tests/enum_single_letter.out
new file mode 100644
index 0000000000..b509c5e2a5
--- /dev/null
+++ b/vlib/v/checker/tests/enum_single_letter.out
@@ -0,0 +1,5 @@
+vlib/v/checker/tests/enum_single_letter.vv:1:6: error: single letter capital names are reserved for generic template types.
+    1 | enum E {
+      |      ^
+    2 |     v w
+    3 | }
diff --git a/vlib/v/checker/tests/enum_single_letter.vv b/vlib/v/checker/tests/enum_single_letter.vv
new file mode 100644
index 0000000000..ef7bc65cec
--- /dev/null
+++ b/vlib/v/checker/tests/enum_single_letter.vv
@@ -0,0 +1,4 @@
+enum E {
+    v w
+}
+println(E.v)
diff --git a/vlib/v/parser/parse_type.v b/vlib/v/parser/parse_type.v
index 977058c9eb..ec596e3275 100644
--- a/vlib/v/parser/parse_type.v
+++ b/vlib/v/parser/parse_type.v
@@ -206,7 +206,7 @@ pub fn (mut p Parser) parse_any_type(language table.Language, is_ptr, check_dot
 		}
 	} else if p.expr_mod != '' {
 		name = p.expr_mod + '.' + name
-	} else if p.mod != 'builtin' && name !in p.table.type_idxs && name.len > 1 {
+	} else if p.mod != 'builtin' && name.len > 1 && name !in p.table.type_idxs {
 		// `Foo` in module `mod` means `mod.Foo`
 		name = p.mod + '.' + name
 	}
diff --git a/vlib/v/parser/parser.v b/vlib/v/parser/parser.v
index 214af5f08f..6461709d8e 100644
--- a/vlib/v/parser/parser.v
+++ b/vlib/v/parser/parser.v
@@ -1723,6 +1723,10 @@ fn (mut p Parser) enum_decl() ast.EnumDecl {
 	p.check(.key_enum)
 	end_pos := p.tok.position()
 	enum_name := p.check_name()
+	if enum_name.len == 1 {
+		p.error_with_pos('single letter capital names are reserved for generic template types.',
+			end_pos)
+	}
 	name := p.prepend_mod(enum_name)
 	p.check(.lcbr)
 	enum_decl_comments := p.eat_comments()