[PATCH] D55955: Properly diagnose [[nodiscard]] on the body of a range-based for loop

[Richard Smith - zygoloid via Phabricator via cfe-commits]

rsmith added inline comments.


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Comment at: include/clang/Sema/Sema.h:5337
   ExprResult ActOnFinishFullExpr(Expr *Expr, SourceLocation CC,
-                                 bool DiscardedValue = false,
+                                 bool WarnOnDiscardedValue = false,
                                  bool IsConstexpr = false);
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Why "WarnOn"? Shouldn't this flag simply indicate whether the expression is a discarded-value expression?


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Comment at: lib/Parse/ParseStmt.cpp:23
 #include "clang/Sema/Scope.h"
+#include "clang/Sema/ScopeInfo.h"
 #include "clang/Sema/TypoCorrection.h"
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The parser shouldn't be looking inside Sema's data structures. Can you add a method to the Sema interface for the query you make below instead?


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Comment at: lib/Sema/SemaExprCXX.cpp:7785
 
-  if (DiscardedValue) {
+  if (WarnOnDiscardedValue) {
     // Top-level expressions default to 'id' when we're in a debugger.
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It doesn't make sense for a WarnOn flag to control how we build the AST like this.


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Comment at: lib/Sema/TreeTransform.h:3297
 
-      return getSema().ActOnExprStmt(E);
+      return getSema().ActOnExprStmt(E, SuppressWarnOnUnusedExpr == 0);
     }
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What happens if the last statement in an expression statement contains a lambda? Will we consider all expression statements in it as not being discarded-value expressions? Alternate suggestion below.


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Comment at: lib/Sema/TreeTransform.h:6529
+      --SuppressWarnOnUnusedExpr;
+    
     if (Result.isInvalid()) {
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Instead of this counter mechanism (which doesn't seem reliable), can you just pass a flag to TransformStmt?


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D55955/new/

https://reviews.llvm.org/D55955