[clang] [clang-repl] Enable `VerifyDiagnostic` support for virtual buffers (PR #182044)

[via cfe-commits]

https://github.com/devajithvs updated https://github.com/llvm/llvm-project/pull/182044

>From 898f9dae0080fc83c3b162e813cd386dba279c4d Mon Sep 17 00:00:00 2001
From: Devajith Valaparambil Sreeramaswamy
 <devajith.valaparambil.sreeramaswamy at cern.ch>
Date: Thu, 19 Feb 2026 10:17:33 +0100
Subject: [PATCH] [clang-repl] Register incremental buffers as virtual files

Instead of using memory buffers without file backing, this patch
registers `input_line_N` buffers as virtual files in the `FileManager`.

This allows `VerifyDiagnosticConsumer` to resolve these buffers using
standard file lookup mechanisms.
---
 clang/lib/Frontend/VerifyDiagnosticConsumer.cpp | 14 ++++++++++++++
 clang/lib/Interpreter/IncrementalParser.cpp     | 13 +++++++++++--
 clang/test/Interpreter/verify-diagnostics.cpp   | 16 ++++++++++++++++
 3 files changed, 41 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/Interpreter/verify-diagnostics.cpp

diff --git a/clang/lib/Frontend/VerifyDiagnosticConsumer.cpp b/clang/lib/Frontend/VerifyDiagnosticConsumer.cpp
index e263e10bb065a..586619c9ad1ce 100644
--- a/clang/lib/Frontend/VerifyDiagnosticConsumer.cpp
+++ b/clang/lib/Frontend/VerifyDiagnosticConsumer.cpp
@@ -516,6 +516,15 @@ static bool ParseDirective(StringRef S, ExpectedData *ED, SourceManager &SM,
     bool MatchAnyLine = false;
     if (!PH.Next("@")) {
       ExpectedLoc = Pos;
+
+      // If an implicit directive is found in an incremental input buffer, allow
+      // it to match any other incremental input buffer
+      StringRef CurrentBufferName =
+          SM.getBufferOrFake(SM.getFileID(Pos)).getBufferIdentifier();
+
+      if (CurrentBufferName.starts_with("input_line_"))
+        MatchAnyFileAndLine = true;
+
     } else {
       PH.Advance();
       unsigned Line = 0;
@@ -556,6 +565,11 @@ static bool ParseDirective(StringRef S, ExpectedData *ED, SourceManager &SM,
           OptionalFileEntryRef File =
               PP->LookupFile(Pos, Filename, false, nullptr, nullptr, nullptr,
                              nullptr, nullptr, nullptr, nullptr, nullptr);
+
+          // Check if the file was virtual
+          if (!File)
+            File = SM.getFileManager().getOptionalFileRef(Filename);
+
           if (!File) {
             Diags.Report(Pos.getLocWithOffset(PH.C - PH.Begin),
                          diag::err_verify_missing_file)
diff --git a/clang/lib/Interpreter/IncrementalParser.cpp b/clang/lib/Interpreter/IncrementalParser.cpp
index bf08911e23533..2d5c1fecda2f5 100644
--- a/clang/lib/Interpreter/IncrementalParser.cpp
+++ b/clang/lib/Interpreter/IncrementalParser.cpp
@@ -129,8 +129,17 @@ IncrementalParser::Parse(llvm::StringRef input) {
   SourceLocation NewLoc = SM.getLocForStartOfFile(SM.getMainFileID());
 
   // Create FileID for the current buffer.
-  FileID FID = SM.createFileID(std::move(MB), SrcMgr::C_User, /*LoadedID=*/0,
-                               /*LoadedOffset=*/0, NewLoc);
+  FileID FID;
+  // Create FileEntry and FileID for the current buffer.
+  FileEntryRef FE = SM.getFileManager().getVirtualFileRef(
+      SourceName.str(), InputSize, 0 /* mod time*/);
+  SM.overrideFileContents(FE, std::move(MB));
+
+  // Ensure HeaderFileInfo exists before lookup to prevent assertion
+  HeaderSearch &HS = PP.getHeaderSearchInfo();
+  HS.getFileInfo(FE);
+
+  FID = SM.createFileID(FE, NewLoc, SrcMgr::C_User);
 
   // NewLoc only used for diags.
   if (PP.EnterSourceFile(FID, /*DirLookup=*/nullptr, NewLoc))
diff --git a/clang/test/Interpreter/verify-diagnostics.cpp b/clang/test/Interpreter/verify-diagnostics.cpp
new file mode 100644
index 0000000000000..7187a77379846
--- /dev/null
+++ b/clang/test/Interpreter/verify-diagnostics.cpp
@@ -0,0 +1,16 @@
+// REQUIRES: host-supports-jit
+// RUN: cat %s | clang-repl -Xcc -Xclang -Xcc -verify
+
+auto x = unknown_val;
+// expected-error at input_line_4:1 {{use of undeclared identifier 'unknown_val'}}
+
+int get_int() { return 42; }
+char* ptr = get_int();
+// expected-error at input_line_8:1 {{cannot initialize a variable of type 'char *' with an rvalue of type 'int'}}
+
+// Verify without input_line_*
+int y = ;
+// expected-error {{expected expression}}
+
+const char* a = "test"; // expected-note {{previous definition is here}}
+const char* a = ""; // expected-error {{redefinition of 'a'}}