Merge pull request swiftlang#36404 from CodaFi/unprecedented-actions

Author: swift-ci

include/swift/AST/Decl.h

@@ -6977,6 +6977,11 @@ class PrecedenceGroupDecl : public Decl {
     return HigherThanLoc;
   }
 
+  /// Retrieve the array of \c Relation objects containing those precedence
+  /// groups with higher precedence than this precedence group.
+  ///
+  /// The elements of this array may be invalid, in which case they will have
+  /// null \c PrecedenceGroupDecl elements.
   ArrayRef<Relation> getHigherThan() const {
     return { getHigherThanBuffer(), NumHigherThan };
   }
@@ -6994,6 +6999,11 @@ class PrecedenceGroupDecl : public Decl {
     return LowerThanLoc;
   }
 
+  /// Retrieve the array of \c Relation objects containing those precedence
+  /// groups with lower precedence than this precedence group.
+  ///
+  /// The elements of this array may be invalid, in which case they will have
+  /// null \c PrecedenceGroupDecl elements.
   ArrayRef<Relation> getLowerThan() const {
     return { getLowerThanBuffer(), NumLowerThan };
   }

lib/Sema/TypeCheckAccess.cpp

@@ -1797,6 +1797,12 @@ class DeclAvailabilityChecker : public DeclVisitor<DeclAvailabilityChecker> {
   void checkPrecedenceGroup(const PrecedenceGroupDecl *PGD,
                             const Decl *refDecl, SourceLoc diagLoc,
                             SourceRange refRange) {
+    // Bail on invalid predence groups. This can happen when the user spells a
+    // relation element that doesn't actually exist.
+    if (!PGD) {
+      return;
+    }
+
     const SourceFile *SF = refDecl->getDeclContext()->getParentSourceFile();
     ModuleDecl *M = PGD->getModuleContext();
     if (!SF->isImportedImplementationOnly(M))

lib/Serialization/Serialization.cpp

@@ -3158,10 +3158,14 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
     auto associativity = getRawStableAssociativity(group->getAssociativity());
 
     SmallVector<DeclID, 8> relations;
-    for (auto &rel : group->getHigherThan())
+    for (auto &rel : group->getHigherThan()) {
+      assert(rel.Group && "Undiagnosed invalid precedence group!");
       relations.push_back(S.addDeclRef(rel.Group));
-    for (auto &rel : group->getLowerThan())
+    }
+    for (auto &rel : group->getLowerThan()) {
+      assert(rel.Group && "Undiagnosed invalid precedence group!");
       relations.push_back(S.addDeclRef(rel.Group));
+    }
 
     unsigned abbrCode = S.DeclTypeAbbrCodes[PrecedenceGroupLayout::Code];
     PrecedenceGroupLayout::emitRecord(S.Out, S.ScratchRecord, abbrCode,

validation-test/compiler_crashers_2_fixed/rdar75248642.swift

@@ -0,0 +1,8 @@
+// RUN: not %target-swift-frontend -typecheck %s
+
+precedencegroup MyOperatorPrecedence {
+  lowerThan: MultiplicationPrecedence
+  higherThan: AdditionPrec
+  associativity: left
+  assignment: false
+}