From 6748240e59d74b823097438c11f3807093139211 Mon Sep 17 00:00:00 2001
From: Yingchi Long <i@lyc.dev>
Date: Fri, 26 Apr 2024 13:49:28 +0800
Subject: [PATCH] libnixf: omit pedantic liveness warning on lambda arg (#464)

---
 libnixf/src/Sema/VariableLookup.cpp           |  5 ++
 .../nixd/test/diagnostic-liveness-formal.md   | 62 +++++++++++++++++++
 nixd/tools/nixd/test/diagnostic-liveness.md   | 23 +------
 3 files changed, 68 insertions(+), 22 deletions(-)
 create mode 100644 nixd/tools/nixd/test/diagnostic-liveness-formal.md

diff --git a/libnixf/src/Sema/VariableLookup.cpp b/libnixf/src/Sema/VariableLookup.cpp
index b56e1ac49..70040124a 100644
--- a/libnixf/src/Sema/VariableLookup.cpp
+++ b/libnixf/src/Sema/VariableLookup.cpp
@@ -43,6 +43,11 @@ bool EnvNode::isLive() const {
 void VariableLookupAnalysis::emitEnvLivenessWarning(
     const std::shared_ptr<EnvNode> &NewEnv) {
   for (const auto &[Name, Def] : NewEnv->defs()) {
+    // If the definition comes from lambda arg, omit the diagnostic
+    // because there is no elegant way to "fix" this trivially & keep
+    // the lambda signature.
+    if (Def->source() == Definition::DS_LambdaArg)
+      continue;
     if (Def->uses().empty()) {
       Diagnostic &D = Diags.emplace_back(Diagnostic::DK_DefinitionNotUsed,
                                          Def->syntax()->range());
diff --git a/nixd/tools/nixd/test/diagnostic-liveness-formal.md b/nixd/tools/nixd/test/diagnostic-liveness-formal.md
new file mode 100644
index 000000000..4fc39b44b
--- /dev/null
+++ b/nixd/tools/nixd/test/diagnostic-liveness-formal.md
@@ -0,0 +1,62 @@
+# RUN: nixd --lit-test < %s | FileCheck %s
+
+<-- initialize(0)
+
+```json
+{
+   "jsonrpc":"2.0",
+   "id":0,
+   "method":"initialize",
+   "params":{
+      "processId":123,
+      "rootPath":"",
+      "capabilities":{
+      },
+      "trace":"off"
+   }
+}
+```
+
+
+<-- textDocument/didOpen
+
+```json
+{
+   "jsonrpc":"2.0",
+   "method":"textDocument/didOpen",
+   "params":{
+      "textDocument":{
+         "uri":"file:///basic.nix",
+         "languageId":"nix",
+         "version":1,
+         "text":"{x, y}: x + 1"
+      }
+   }
+}
+```
+
+```
+     CHECK: "diagnostics": [
+CHECK-NEXT:   {
+CHECK-NEXT:     "code": "sema-def-not-used",
+CHECK-NEXT:     "message": "definition `y` is not used",
+CHECK-NEXT:     "range": {
+CHECK-NEXT:       "end": {
+CHECK-NEXT:         "character": 5,
+CHECK-NEXT:         "line": 0
+CHECK-NEXT:       },
+CHECK-NEXT:       "start": {
+CHECK-NEXT:         "character": 4,
+CHECK-NEXT:         "line": 0
+CHECK-NEXT:       }
+CHECK-NEXT:     },
+CHECK-NEXT:     "relatedInformation": [],
+CHECK-NEXT:     "severity": 2,
+CHECK-NEXT:     "source": "nixf",
+CHECK-NEXT:     "tags": [
+CHECK-NEXT:       1
+CHECK-NEXT:     ]
+CHECK-NEXT:   }
+CHECK-NEXT: ],
+CHECK-NEXT: "uri": "file:///basic.nix",
+```
diff --git a/nixd/tools/nixd/test/diagnostic-liveness.md b/nixd/tools/nixd/test/diagnostic-liveness.md
index 06fec9492..e8ec72c09 100644
--- a/nixd/tools/nixd/test/diagnostic-liveness.md
+++ b/nixd/tools/nixd/test/diagnostic-liveness.md
@@ -36,28 +36,7 @@
 ```
 
 ```
-     CHECK: "diagnostics": [
-CHECK-NEXT:   {
-CHECK-NEXT:     "code": "sema-def-not-used",
-CHECK-NEXT:     "message": "definition `y` is not used",
-CHECK-NEXT:     "range": {
-CHECK-NEXT:       "end": {
-CHECK-NEXT:         "character": 4,
-CHECK-NEXT:         "line": 0
-CHECK-NEXT:       },
-CHECK-NEXT:       "start": {
-CHECK-NEXT:         "character": 3,
-CHECK-NEXT:         "line": 0
-CHECK-NEXT:       }
-CHECK-NEXT:     },
-CHECK-NEXT:     "relatedInformation": [],
-CHECK-NEXT:     "severity": 2,
-CHECK-NEXT:     "source": "nixf",
-CHECK-NEXT:     "tags": [
-CHECK-NEXT:       1
-CHECK-NEXT:     ]
-CHECK-NEXT:   }
-CHECK-NEXT: ],
+     CHECK: "diagnostics": [],
 CHECK-NEXT: "uri": "file:///basic.nix",
 CHECK-NEXT: "version": 1
 ```