From 0fd0855da01b4a25bb73eaebf570080ceb93a50c Mon Sep 17 00:00:00 2001
From: Amr Hesham <amr96@programmer.net>
Date: Thu, 13 Apr 2023 01:24:29 +0200
Subject: [PATCH] Detect duplicate struct member names  (#2764)

Detect struct literal or struct type literal member duplicate name

Closes #2762
---
 explorer/interpreter/resolve_names.cpp          | 17 +++++++++++++++--
 .../fail_struct_literal_duplicate_member.carbon | 15 +++++++++++++++
 ..._struct_type_literal_duplicate_member.carbon | 15 +++++++++++++++
 3 files changed, 45 insertions(+), 2 deletions(-)
 create mode 100644 explorer/testdata/struct/fail_struct_literal_duplicate_member.carbon
 create mode 100644 explorer/testdata/struct/fail_struct_type_literal_duplicate_member.carbon

diff --git a/explorer/interpreter/resolve_names.cpp b/explorer/interpreter/resolve_names.cpp
index e4aad27f9bd2..0e2c2e2ee709 100644
--- a/explorer/interpreter/resolve_names.cpp
+++ b/explorer/interpreter/resolve_names.cpp
@@ -320,19 +320,32 @@ auto NameResolver::ResolveNames(Expression& expression,
         CARBON_RETURN_IF_ERROR(ResolveNames(*field, enclosing_scope));
       }
       break;
-    case ExpressionKind::StructLiteral:
+    case ExpressionKind::StructLiteral: {
+      std::set<std::string_view> member_names;
       for (FieldInitializer& init : cast<StructLiteral>(expression).fields()) {
         CARBON_RETURN_IF_ERROR(
             ResolveNames(init.expression(), enclosing_scope));
+        if (!member_names.insert(init.name()).second) {
+          return ProgramError(init.expression().source_loc())
+                 << "Duplicate name `" << init.name() << "` in struct literal";
+        }
       }
       break;
-    case ExpressionKind::StructTypeLiteral:
+    }
+    case ExpressionKind::StructTypeLiteral: {
+      std::set<std::string_view> member_names;
       for (FieldInitializer& init :
            cast<StructTypeLiteral>(expression).fields()) {
         CARBON_RETURN_IF_ERROR(
             ResolveNames(init.expression(), enclosing_scope));
+        if (!member_names.insert(init.name()).second) {
+          return ProgramError(init.expression().source_loc())
+                 << "Duplicate name `" << init.name()
+                 << "` in struct type literal";
+        }
       }
       break;
+    }
     case ExpressionKind::IdentifierExpression: {
       auto& identifier = cast<IdentifierExpression>(expression);
       CARBON_ASSIGN_OR_RETURN(
diff --git a/explorer/testdata/struct/fail_struct_literal_duplicate_member.carbon b/explorer/testdata/struct/fail_struct_literal_duplicate_member.carbon
new file mode 100644
index 000000000000..00d68caf137b
--- /dev/null
+++ b/explorer/testdata/struct/fail_struct_literal_duplicate_member.carbon
@@ -0,0 +1,15 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// AUTOUPDATE
+// RUN: %{not} %{explorer-run}
+// RUN: %{not} %{explorer-run-trace}
+
+package ExplorerTest api;
+
+fn Main() -> i32 {
+  // CHECK:STDERR: COMPILATION ERROR: {{.*}}/explorer/testdata/struct/fail_struct_literal_duplicate_member.carbon:[[@LINE+1]]: Duplicate name `x` in struct literal
+  var x: auto = {.x = 0, .x = 0};
+  return 0;
+}
diff --git a/explorer/testdata/struct/fail_struct_type_literal_duplicate_member.carbon b/explorer/testdata/struct/fail_struct_type_literal_duplicate_member.carbon
new file mode 100644
index 000000000000..c4d105204ec5
--- /dev/null
+++ b/explorer/testdata/struct/fail_struct_type_literal_duplicate_member.carbon
@@ -0,0 +1,15 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// AUTOUPDATE
+// RUN: %{not} %{explorer-run}
+// RUN: %{not} %{explorer-run-trace}
+
+package ExplorerTest api;
+
+fn Main() -> i32 {
+  // CHECK:STDERR: COMPILATION ERROR: {{.*}}/explorer/testdata/struct/fail_struct_type_literal_duplicate_member.carbon:[[@LINE+1]]: Duplicate name `x` in struct type literal
+  var y: {.x: i32, .x: i32};
+  return 0;
+}