From fdf80e86a52849813d05da4b6c25884c06ba9e98 Mon Sep 17 00:00:00 2001
From: Saar Raz <saar@raz.email>
Date: Fri, 6 Dec 2019 01:30:21 +0200
Subject: [Concepts] Constraint Enforcement & Diagnostics

Part of the C++20 concepts implementation effort.
- Associated constraints (requires clauses, currently) are now enforced when instantiating/specializing templates and when considering partial specializations and function overloads.
- Elaborated diagnostics give helpful insight as to why the constraints were not satisfied.
Phabricator: D41569

Re-commit, after fixing some memory bugs.
---
 clang/lib/Serialization/ASTReaderStmt.cpp | 24 ++++++++++++++++++++++--
 clang/lib/Serialization/ASTWriterStmt.cpp | 20 +++++++++++++++++++-
 2 files changed, 41 insertions(+), 3 deletions(-)

(limited to 'clang/lib/Serialization')

diff --git a/clang/lib/Serialization/ASTReaderStmt.cpp b/clang/lib/Serialization/ASTReaderStmt.cpp
index f426ed3b8d3..815a9744c5b 100644
--- a/clang/lib/Serialization/ASTReaderStmt.cpp
+++ b/clang/lib/Serialization/ASTReaderStmt.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Serialization/ASTReader.h"
+#include "clang/AST/ASTConcept.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/AttrIterator.h"
 #include "clang/AST/Decl.h"
@@ -742,14 +743,33 @@ void ASTStmtReader::VisitConceptSpecializationExpr(
   E->TemplateKWLoc = Record.readSourceLocation();
   E->ConceptNameLoc = Record.readSourceLocation();
   E->FoundDecl = ReadDeclAs<NamedDecl>();
-  E->NamedConcept.setPointer(ReadDeclAs<ConceptDecl>());
+  E->NamedConcept = ReadDeclAs<ConceptDecl>();
   const ASTTemplateArgumentListInfo *ArgsAsWritten =
       Record.readASTTemplateArgumentListInfo();
   llvm::SmallVector<TemplateArgument, 4> Args;
   for (unsigned I = 0; I < NumTemplateArgs; ++I)
     Args.push_back(Record.readTemplateArgument());
   E->setTemplateArguments(ArgsAsWritten, Args);
-  E->NamedConcept.setInt(Record.readInt() == 1);
+  ConstraintSatisfaction Satisfaction;
+  Satisfaction.IsSatisfied = Record.readInt();
+  if (!Satisfaction.IsSatisfied) {
+    unsigned NumDetailRecords = Record.readInt();
+    for (unsigned i = 0; i != NumDetailRecords; ++i) {
+      Expr *ConstraintExpr = Record.readExpr();
+      bool IsDiagnostic = Record.readInt();
+      if (IsDiagnostic) {
+        SourceLocation DiagLocation = Record.readSourceLocation();
+        std::string DiagMessage = Record.readString();
+        Satisfaction.Details.emplace_back(
+            ConstraintExpr, new (Record.getContext())
+                                ConstraintSatisfaction::SubstitutionDiagnostic{
+                                    DiagLocation, DiagMessage});
+      } else
+        Satisfaction.Details.emplace_back(ConstraintExpr, Record.readExpr());
+    }
+  }
+  E->Satisfaction = ASTConstraintSatisfaction::Create(Record.getContext(),
+                                                      Satisfaction);
 }
 
 void ASTStmtReader::VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
diff --git a/clang/lib/Serialization/ASTWriterStmt.cpp b/clang/lib/Serialization/ASTWriterStmt.cpp
index 2b331a97985..1e801d02afc 100644
--- a/clang/lib/Serialization/ASTWriterStmt.cpp
+++ b/clang/lib/Serialization/ASTWriterStmt.cpp
@@ -401,7 +401,25 @@ void ASTStmtWriter::VisitConceptSpecializationExpr(
   Record.AddASTTemplateArgumentListInfo(E->getTemplateArgsAsWritten());
   for (const TemplateArgument &Arg : TemplateArgs)
     Record.AddTemplateArgument(Arg);
-  Record.push_back(E->isSatisfied());
+  const ASTConstraintSatisfaction &Satisfaction = E->getSatisfaction();
+  Record.push_back(Satisfaction.IsSatisfied);
+  if (!Satisfaction.IsSatisfied) {
+    Record.push_back(Satisfaction.NumRecords);
+    for (const auto &DetailRecord : Satisfaction) {
+      Record.AddStmt(const_cast<Expr *>(DetailRecord.first));
+      auto *E = DetailRecord.second.dyn_cast<Expr *>();
+      Record.push_back(E == nullptr);
+      if (E)
+        Record.AddStmt(E);
+      else {
+        auto *Diag = DetailRecord.second.get<std::pair<SourceLocation,
+                                                       StringRef> *>();
+        Record.AddSourceLocation(Diag->first);
+        Record.AddString(Diag->second);
+      }
+    }
+  }
+
   Code = serialization::EXPR_CONCEPT_SPECIALIZATION;
 }
 
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