[PATCH] D157526: [clang][Sema] Remove irrelevant diagnostics from constraint satisfaction failure

[Takuya Shimizu via Phabricator via cfe-commits]

hazohelet created this revision.
hazohelet added reviewers: aaron.ballman, erichkeane, tbaeder, shafik.
Herald added a project: All.
hazohelet requested review of this revision.
Herald added a project: clang.

BEFORE this patch, when clang handles constraints like `C1 || C2` where `C1` evaluates to false and `C2` evaluates to true, it emitted irrelevant diagnostics about the falsity of `C1`.
This patch removes the irrelevant diagnostic information generated during the evaluation of `C1` if `C2` evaluates to true.

Fixes https://github.com/llvm/llvm-project/issues/54678


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D157526

Files:
  clang/docs/ReleaseNotes.rst
  clang/lib/Sema/SemaConcept.cpp
  clang/test/SemaTemplate/concepts.cpp


Index: clang/test/SemaTemplate/concepts.cpp
===================================================================
--- clang/test/SemaTemplate/concepts.cpp
+++ clang/test/SemaTemplate/concepts.cpp
@@ -994,3 +994,40 @@
 }
 
 }
+
+namespace GH54678 {
+template<class>
+concept True = true;
+
+template<class>
+concept False = false; // expected-note 9 {{'false' evaluated to false}}
+
+template<class>
+concept Irrelevant = false;
+
+template <typename T>
+concept ErrorRequires = requires(ErrorRequires auto x) { x; }; // expected-error {{unknown type name 'ErrorRequires'}}
+
+template<class T> void aaa(T t) // expected-note {{candidate template ignored: constraints not satisfied}}
+requires (False<T> || False<T>) || False<T> {} // expected-note 3 {{'int' does not satisfy 'False'}}
+template<class T> void bbb(T t) // expected-note {{candidate template ignored: constraints not satisfied}}
+requires (False<T> || False<T>) && True<T> {} // expected-note 2 {{'long' does not satisfy 'False'}}
+template<class T> void ccc(T t) // expected-note {{candidate template ignored: constraints not satisfied}}
+requires (True<T> || Irrelevant<T>) && False<T> {} // expected-note {{'unsigned long' does not satisfy 'False'}}
+template<class T> void ddd(T t) // expected-note {{candidate template ignored: constraints not satisfied}}
+requires (Irrelevant<T> || True<T>) && False<T> {} // expected-note {{'int' does not satisfy 'False'}}
+template<class T> void eee(T t) // expected-note {{candidate template ignored: constraints not satisfied}}
+requires (Irrelevant<T> || Irrelevant<T> || True<T>) && False<T> {} // expected-note {{'long' does not satisfy 'False'}}
+
+template<class T> void fff(T t) // expected-note {{candidate template ignored: constraints not satisfied}}
+requires((ErrorRequires<T> || False<T> || True<T>) && False<T>) {} // expected-note {{'unsigned long' does not satisfy 'False'}}
+
+void test() {
+    aaa(42); // expected-error {{no matching function}}
+    bbb(42L); // expected-error{{no matching function}}
+    ccc(42UL); // expected-error {{no matching function}}
+    ddd(42); // expected-error {{no matching function}}
+    eee(42L); // expected-error {{no matching function}}
+    fff(42UL); // expected-error {{no matching function}}
+}
+}
Index: clang/lib/Sema/SemaConcept.cpp
===================================================================
--- clang/lib/Sema/SemaConcept.cpp
+++ clang/lib/Sema/SemaConcept.cpp
@@ -183,6 +183,7 @@
   ConstraintExpr = ConstraintExpr->IgnoreParenImpCasts();
 
   if (LogicalBinOp BO = ConstraintExpr) {
+    auto EffectiveDetailEnd = Satisfaction.Details.end();
     ExprResult LHSRes = calculateConstraintSatisfaction(
         S, BO.getLHS(), Satisfaction, Evaluator);
 
@@ -216,6 +217,11 @@
     if (RHSRes.isInvalid())
       return ExprError();
 
+    bool IsRHSSatisfied = Satisfaction.IsSatisfied;
+    if (BO.isOr() && IsRHSSatisfied)
+      Satisfaction.Details.erase(EffectiveDetailEnd,
+                                 Satisfaction.Details.end());
+
     return BO.recreateBinOp(S, LHSRes, RHSRes);
   }
 
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -125,6 +125,8 @@
   of a base class is not called in the constructor of its derived class.
 - Clang no longer emits ``-Wmissing-variable-declarations`` for variables declared
   with the ``register`` storage class.
+- Clang no longer emits irrelevant notes about unsatisfied constraint expressions
+  on the left-hand side of ``||`` when the right-hand side constraint is satisfied.
 
 Bug Fixes in This Version
 -------------------------


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