https://github.com/bala-bhargav created https://github.com/llvm/llvm-project/pull/178661
In clang-repl, expressions typed without a semicolon have their values printed to the console. This means the return value is actually being used, not discarded. However, the compiler was emitting `[[nodiscard]]` warnings because it didn't know the REPL would use the value for printing. This fix detects when we're in REPL mode evaluating a top-level expression and skips the warning, since printing the result counts as "using" it. >From 6e20778fba945ba847fa0ff7f960b67c8ab54d56 Mon Sep 17 00:00:00 2001 From: bhargav <[email protected]> Date: Thu, 29 Jan 2026 19:28:04 +0530 Subject: [PATCH] [clang-repl] Suppress [[nodiscard]] warnings for REPL printed expressions In clang-repl, expressions without semicolons have their values printed by the value printing mechanism. Since the result is used (for printing), we should not emit [[nodiscard]] warnings for these expressions. This fixes the false positive warning when evaluating expressions like v.size() in the REPL. --- clang/lib/Sema/SemaStmt.cpp | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp index 5ab10fdfc7b74..468bb4a544026 100644 --- a/clang/lib/Sema/SemaStmt.cpp +++ b/clang/lib/Sema/SemaStmt.cpp @@ -239,6 +239,16 @@ void DiagnoseUnused(Sema &S, const Expr *E, std::optional<unsigned> DiagID) { if (S.isUnevaluatedContext()) return; + // In incremental processing mode (REPL), expressions inside TopLevelStmtDecl + // without a semicolon will have their values printed by the value printing + // mechanism. The result is therefore "used" and we should not warn about + // [[nodiscard]] attributes. + if (S.PP.isIncrementalProcessingEnabled()) { + if (isa<TopLevelStmtDecl>(S.CurContext)) + return; + } + + SourceLocation ExprLoc = E->IgnoreParenImpCasts()->getExprLoc(); // In most cases, we don't want to warn if the expression is written in a // macro body, or if the macro comes from a system header. If the offending _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
