From be8be3d3192be0ee89673245877cd1d401999e8f Mon Sep 17 00:00:00 2001
From: shadowninja55 <49539636+shadowninja55@users.noreply.github.com>
Date: Fri, 25 Jun 2021 06:08:56 -0400
Subject: [PATCH] v.parser: prohibit redeclaration of builtin types (#10563)

---
 vlib/eventbus/README.md                       |  8 +-
 vlib/v/ast/table.v                            | 81 +++++++++++--------
 ...rohibit_redeclaration_of_builtin_types.out |  3 +
 ...prohibit_redeclaration_of_builtin_types.vv |  1 +
 4 files changed, 59 insertions(+), 34 deletions(-)
 create mode 100644 vlib/v/parser/tests/prohibit_redeclaration_of_builtin_types.out
 create mode 100644 vlib/v/parser/tests/prohibit_redeclaration_of_builtin_types.vv

diff --git a/vlib/eventbus/README.md b/vlib/eventbus/README.md
index 90d2e3d1d..93047db53 100644
--- a/vlib/eventbus/README.md
+++ b/vlib/eventbus/README.md
@@ -85,18 +85,22 @@ fn on_error(receiver voidptr, e &Error, work &Work) {
 ```v oksyntax
 module main
 
+import eventbus
+
+const eb = eventbus.new()
+
 struct Work {
 	hours int
 }
 
-struct Error {
+struct AnError {
 	message string
 }
 
 fn do_work() {
 	work := Work{20}
 	// get a mutable Params instance & put some data into it
-	error := &Error{'Error: no internet connection.'}
+	error := &AnError{'Error: no internet connection.'}
 	// publish the event
 	eb.publish('error', work, error)
 }
diff --git a/vlib/v/ast/table.v b/vlib/v/ast/table.v
index ff4376f53..966423217 100644
--- a/vlib/v/ast/table.v
+++ b/vlib/v/ast/table.v
@@ -542,44 +542,61 @@ pub fn (t &Table) unalias_num_type(typ Type) Type {
 	return typ
 }
 
-[inline]
-pub fn (mut t Table) register_type_symbol(typ TypeSymbol) int {
-	// println('register_type_symbol( $typ.name )')
-	existing_idx := t.type_idxs[typ.name]
-	if existing_idx > 0 {
-		ex_type := t.type_symbols[existing_idx]
-		match ex_type.kind {
-			.placeholder {
-				// override placeholder
-				// println('overriding type placeholder `$typ.name`')
-				t.type_symbols[existing_idx] = {
-					...typ
-					methods: ex_type.methods
-				}
-				return existing_idx
+fn (mut t Table) check_for_already_registered_symbol(typ TypeSymbol, existing_idx int) int {
+	ex_type := t.type_symbols[existing_idx]
+	match ex_type.kind {
+		.placeholder {
+			// override placeholder
+			// println('overriding type placeholder `$typ.name`')
+			t.type_symbols[existing_idx] = {
+				...typ
+				methods: ex_type.methods
 			}
-			else {
-				// builtin
-				// this will override the already registered builtin types
-				// with the actual v struct declaration in the source
-				if (existing_idx >= string_type_idx && existing_idx <= map_type_idx)
-					|| existing_idx == error_type_idx {
-					if existing_idx == string_type_idx {
-						// existing_type := t.type_symbols[existing_idx]
-						t.type_symbols[existing_idx] = TypeSymbol{
-							...typ
-							kind: ex_type.kind
-						}
-					} else {
-						t.type_symbols[existing_idx] = typ
+			return existing_idx
+		}
+		else {
+			// builtin
+			// this will override the already registered builtin types
+			// with the actual v struct declaration in the source
+			if (existing_idx >= string_type_idx && existing_idx <= map_type_idx)
+				|| existing_idx == error_type_idx {
+				if existing_idx == string_type_idx {
+					// existing_type := t.type_symbols[existing_idx]
+					t.type_symbols[existing_idx] = TypeSymbol{
+						...typ
+						kind: ex_type.kind
 					}
-					return existing_idx
+				} else {
+					t.type_symbols[existing_idx] = typ
 				}
-				return -1
+				return existing_idx
+			}
+			return -1
+		}
+	}
+	return -2
+}
+
+[inline]
+pub fn (mut t Table) register_type_symbol(typ TypeSymbol) int {
+	mut typ_idx := -2
+	mut existing_idx := t.type_idxs[typ.name]
+	if existing_idx > 0 {
+		typ_idx = t.check_for_already_registered_symbol(typ, existing_idx)
+		if typ_idx != -2 {
+			return typ_idx
+		}
+	}
+	if typ.mod == 'main' {
+		existing_idx = t.type_idxs[typ.name.trim_prefix('main.')]
+		if existing_idx > 0 {
+			typ_idx = t.check_for_already_registered_symbol(typ, existing_idx)
+			if typ_idx != -2 {
+				return typ_idx
 			}
 		}
 	}
-	typ_idx := t.type_symbols.len
+	typ_idx = t.type_symbols.len
 	t.type_symbols << typ
 	t.type_idxs[typ.name] = typ_idx
 	return typ_idx
diff --git a/vlib/v/parser/tests/prohibit_redeclaration_of_builtin_types.out b/vlib/v/parser/tests/prohibit_redeclaration_of_builtin_types.out
new file mode 100644
index 000000000..e292e0a01
--- /dev/null
+++ b/vlib/v/parser/tests/prohibit_redeclaration_of_builtin_types.out
@@ -0,0 +1,3 @@
+vlib/v/parser/tests/prohibit_redeclaration_of_builtin_types.vv:1:8: error: cannot register struct `Option`, another type with this name exists
+    1 | struct Option {}
+      |        ~~~~~~
diff --git a/vlib/v/parser/tests/prohibit_redeclaration_of_builtin_types.vv b/vlib/v/parser/tests/prohibit_redeclaration_of_builtin_types.vv
new file mode 100644
index 000000000..26669cca0
--- /dev/null
+++ b/vlib/v/parser/tests/prohibit_redeclaration_of_builtin_types.vv
@@ -0,0 +1 @@
+struct Option {}
-- 
2.30.2