[Diagnostics] Diagnose missing members via fixes

lib/Sema/CSDiag.cpp

@@ -523,10 +523,10 @@ class FailureDiagnosis :public ASTVisitor<FailureDiagnosis, /*exprresult*/bool>{
   /// Given a result of name lookup that had no viable results, diagnose the
   /// unviable ones.
   void diagnoseUnviableLookupResults(MemberLookupResult &lookupResults,
-                                     Type baseObjTy, Expr *baseExpr,
+                                     Expr *expr, Type baseObjTy, Expr *baseExpr,
                                      DeclName memberName, DeclNameLoc nameLoc,
                                      SourceLoc loc);
-  
+
   /// Produce a diagnostic for a general overload resolution failure
   /// (irrespective of the exact expression kind).
   bool diagnoseGeneralOverloadFailure(Constraint *constraint);
@@ -913,125 +913,23 @@ diagnoseTypeMemberOnInstanceLookup(Type baseObjTy,
   return;
 }
 
-/// When a user refers a enum case with a wrong member name, we try to find a enum
-/// element whose name differs from the wrong name only in convention; meaning their
-/// lower case counterparts are identical.
-///   - DeclName is valid when such a correct case is found; invalid otherwise.
-static DeclName
-findCorrectEnumCaseName(Type Ty, TypoCorrectionResults &corrections,
-                        DeclName memberName) {
-  if (memberName.isSpecial() || !memberName.isSimpleName())
-    return DeclName();
-  if (!Ty->is<EnumType>() &&
-      !Ty->is<BoundGenericEnumType>())
-    return DeclName();
-  auto candidate =
-    corrections.getUniqueCandidateMatching([&](ValueDecl *candidate) {
-      return (isa<EnumElementDecl>(candidate) &&
-              candidate->getFullName().getBaseIdentifier().str()
-                .equals_lower(memberName.getBaseIdentifier().str()));
-    });
-  return (candidate ? candidate->getFullName() : DeclName());
-}
-
 /// Given a result of name lookup that had no viable results, diagnose the
 /// unviable ones.
-void FailureDiagnosis::
-diagnoseUnviableLookupResults(MemberLookupResult &result, Type baseObjTy,
-                              Expr *baseExpr,
-                              DeclName memberName, DeclNameLoc nameLoc,
-                              SourceLoc loc) {
+void FailureDiagnosis::diagnoseUnviableLookupResults(
+    MemberLookupResult &result, Expr *E, Type baseObjTy, Expr *baseExpr,
+    DeclName memberName, DeclNameLoc nameLoc, SourceLoc loc) {
   SourceRange baseRange = baseExpr ? baseExpr->getSourceRange() : SourceRange();
-  
+
   // If we found no results at all, mention that fact.
   if (result.UnviableCandidates.empty()) {
-    TypoCorrectionResults corrections(CS.TC, memberName, nameLoc);
-    auto tryTypoCorrection = [&] {
-      CS.TC.performTypoCorrection(CS.DC, DeclRefKind::Ordinary, baseObjTy,
-                                  defaultMemberLookupOptions, corrections);
-    };
-
-    // TODO: This should handle tuple member lookups, like x.1231 as well.
-    if (memberName.getBaseName().getKind() == DeclBaseName::Kind::Subscript) {
-      diagnose(loc, diag::could_not_find_value_subscript, baseObjTy)
-        .highlight(baseRange);
-    } else if (memberName.getBaseName() == "deinit") {
-      // Specialised diagnostic if trying to access deinitialisers
-      diagnose(loc, diag::destructor_not_accessible).highlight(baseRange);
-    } else if (auto metatypeTy = baseObjTy->getAs<MetatypeType>()) {
-      auto instanceTy = metatypeTy->getInstanceType();
-      tryTypoCorrection();
-
-      if (DeclName rightName = findCorrectEnumCaseName(instanceTy,
-                                                       corrections,
-                                                       memberName)) {
-        diagnose(loc, diag::could_not_find_enum_case, instanceTy,
-                 memberName, rightName)
-          .fixItReplace(nameLoc.getBaseNameLoc(),
-                        rightName.getBaseIdentifier().str());
-        return;
-      }
-
-      if (auto correction = corrections.claimUniqueCorrection()) {
-        auto diagnostic =
-          diagnose(loc, diag::could_not_find_type_member_corrected,
-                   instanceTy, memberName, correction->CorrectedName);
-        diagnostic.highlight(baseRange).highlight(nameLoc.getSourceRange());
-        correction->addFixits(diagnostic);
-      } else {
-        diagnose(loc, diag::could_not_find_type_member, instanceTy, memberName)
-          .highlight(baseRange).highlight(nameLoc.getSourceRange());
-      }
-    } else if (auto moduleTy = baseObjTy->getAs<ModuleType>()) {
-      diagnose(baseExpr->getLoc(), diag::no_member_of_module,
-               moduleTy->getModule()->getName(), memberName)
-          .highlight(baseRange)
-          .highlight(nameLoc.getSourceRange());
-      return;
-    } else {
-      auto emitBasicError = [&] {
-        diagnose(loc, diag::could_not_find_value_member,
-                 baseObjTy, memberName)
-          .highlight(baseRange).highlight(nameLoc.getSourceRange());
-      };
-
-      // Check for a few common cases that can cause missing members.
-      if (baseObjTy->is<EnumType>() && memberName.isSimpleName("rawValue")) {
-        auto loc = baseObjTy->castTo<EnumType>()->getDecl()->getNameLoc();
-        if (loc.isValid()) {
-          emitBasicError();
-          diagnose(loc, diag::did_you_mean_raw_type);
-          return;
-        }
-      } else if (baseObjTy->isAny()) {
-        emitBasicError();
-        diagnose(loc, diag::any_as_anyobject_fixit)
-          .fixItInsert(baseExpr->getStartLoc(), "(")
-          .fixItInsertAfter(baseExpr->getEndLoc(), " as AnyObject)");
-        return;
-      }
-
-      tryTypoCorrection();
-
-      if (auto correction = corrections.claimUniqueCorrection()) {
-        auto diagnostic =
-          diagnose(loc, diag::could_not_find_value_member_corrected,
-                   baseObjTy, memberName, correction->CorrectedName);
-        diagnostic.highlight(baseRange).highlight(nameLoc.getSourceRange());
-        correction->addFixits(diagnostic);
-      } else {
-        emitBasicError();
-      }
-    }
-
-    // Note all the correction candidates.
-    corrections.noteAllCandidates();
-
-    // TODO: recover?
+    MissingMemberFailure failure(nullptr, CS, baseObjTy, memberName,
+                                 CS.getConstraintLocator(E));
+    auto diagnosed = failure.diagnoseAsError();
+    assert(diagnosed && "Failed to produce missing member diagnostic");
+    (void)diagnosed;
     return;
   }
 
-
   // Otherwise, we have at least one (and potentially many) viable candidates
   // sort them out.  If all of the candidates have the same problem (commonly
   // because there is exactly one candidate!) diagnose this.
@@ -4632,7 +4530,7 @@ bool FailureDiagnosis::diagnoseMethodAttributeFailures(
   // If one of the unviable candidates matches arguments exactly,
   // that means that actual problem is related to function attributes.
   if (unviableCandidates.closeness == CC_ExactMatch) {
-    diagnoseUnviableLookupResults(results, baseType, base, UDE->getName(),
+    diagnoseUnviableLookupResults(results, UDE, baseType, base, UDE->getName(),
                                   UDE->getNameLoc(), UDE->getLoc());
     return true;
   }
@@ -7458,7 +7356,7 @@ bool FailureDiagnosis::diagnoseMemberFailures(
     }
 
     // FIXME: Dig out the property DeclNameLoc.
-    diagnoseUnviableLookupResults(result, baseObjTy, baseExpr, memberName,
+    diagnoseUnviableLookupResults(result, E, baseObjTy, baseExpr, memberName,
                                   NameLoc, BaseLoc);
     return true;
   }
@@ -8226,6 +8124,20 @@ void FailureDiagnosis::diagnoseAmbiguity(Expr *E) {
     }
   }
 
+  // Before giving up completely let's try to see if there are any
+  // fixes recorded by constraint generator, which point to structural
+  // problems that might not result in solution even if fixed e.g.
+  // missing members involved in protocol composition in expression
+  // context which are interpreted as binary operator expressions instead.
+  {
+    bool diagnosed = false;
+    for (auto *fix : CS.getFixes())
+      diagnosed |= fix->diagnose(expr);
+
+    if (diagnosed)
+      return;
+  }
+
   // If there are no posted constraints or failures, then there was
   // not enough contextual information available to infer a type for the
   // expression.

lib/Sema/CSDiagnostics.cpp

@@ -17,6 +17,7 @@
 #include "CSDiagnostics.h"
 #include "ConstraintSystem.h"
 #include "MiscDiagnostics.h"
+#include "TypoCorrection.h"
 #include "swift/AST/ASTContext.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/Expr.h"
@@ -1332,3 +1333,147 @@ bool SubscriptMisuseFailure::diagnoseAsNote() {
   }
   return false;
 }
+
+/// When a user refers a enum case with a wrong member name, we try to find a
+/// enum element whose name differs from the wrong name only in convention;
+/// meaning their lower case counterparts are identical.
+///   - DeclName is valid when such a correct case is found; invalid otherwise.
+DeclName MissingMemberFailure::findCorrectEnumCaseName(
+    Type Ty, TypoCorrectionResults &corrections, DeclName memberName) {
+  if (memberName.isSpecial() || !memberName.isSimpleName())
+    return DeclName();
+  if (!Ty->getEnumOrBoundGenericEnum())
+    return DeclName();
+  auto candidate =
+      corrections.getUniqueCandidateMatching([&](ValueDecl *candidate) {
+        return (isa<EnumElementDecl>(candidate) &&
+                candidate->getFullName().getBaseIdentifier().str().equals_lower(
+                    memberName.getBaseIdentifier().str()));
+      });
+  return (candidate ? candidate->getFullName() : DeclName());
+}
+
+bool MissingMemberFailure::diagnoseAsError() {
+  auto &TC = getTypeChecker();
+  auto *anchor = getRawAnchor();
+  auto *baseExpr = getAnchor();
+
+  if (!anchor || !baseExpr)
+    return false;
+
+  if (auto *typeVar = BaseType->getAs<TypeVariableType>()) {
+    auto &CS = getConstraintSystem();
+    auto *memberLoc = typeVar->getImpl().getLocator();
+    // Don't try to diagnose anything besides first missing
+    // member in the chain. e.g. `x.foo().bar()` let's make
+    // sure to diagnose only `foo()` as missing because we
+    // don't really know much about what `bar()` is supposed
+    // to be.
+    if (CS.MissingMembers.count(memberLoc))
+      return false;
+  }
+
+  auto baseType = resolveType(BaseType)->getWithoutSpecifierType();
+
+  DeclNameLoc nameLoc(anchor->getStartLoc());
+  if (auto *UDE = dyn_cast<UnresolvedDotExpr>(anchor)) {
+    nameLoc = UDE->getNameLoc();
+  } else if (auto *UME = dyn_cast<UnresolvedMemberExpr>(anchor)) {
+    nameLoc = UME->getNameLoc();
+  }
+
+  auto emitBasicError = [&](Type baseType) {
+    auto diagnostic = diag::could_not_find_value_member;
+
+    if (auto *metatype = baseType->getAs<MetatypeType>()) {
+      baseType = metatype->getInstanceType();
+      diagnostic = diag::could_not_find_type_member;
+    }
+
+    if (baseType->is<TupleType>())
+      diagnostic = diag::could_not_find_tuple_member;
+
+    emitDiagnostic(anchor->getLoc(), diagnostic, baseType, Name)
+        .highlight(baseExpr->getSourceRange())
+        .highlight(nameLoc.getSourceRange());
+  };
+
+  TypoCorrectionResults corrections(TC, Name, nameLoc);
+  auto tryTypoCorrection = [&] {
+    TC.performTypoCorrection(getDC(), DeclRefKind::Ordinary, baseType,
+                             defaultMemberLookupOptions, corrections);
+  };
+
+  if (Name.getBaseName().getKind() == DeclBaseName::Kind::Subscript) {
+    emitDiagnostic(anchor->getLoc(), diag::could_not_find_value_subscript,
+                   baseType)
+        .highlight(baseExpr->getSourceRange());
+  } else if (Name.getBaseName() == "deinit") {
+    // Specialised diagnostic if trying to access deinitialisers
+    emitDiagnostic(anchor->getLoc(), diag::destructor_not_accessible)
+        .highlight(baseExpr->getSourceRange());
+  } else if (auto metatypeTy = baseType->getAs<MetatypeType>()) {
+    auto instanceTy = metatypeTy->getInstanceType();
+    tryTypoCorrection();
+
+    if (DeclName rightName =
+            findCorrectEnumCaseName(instanceTy, corrections, Name)) {
+      emitDiagnostic(anchor->getLoc(), diag::could_not_find_enum_case,
+                     instanceTy, Name, rightName)
+          .fixItReplace(nameLoc.getBaseNameLoc(),
+                        rightName.getBaseIdentifier().str());
+      return true;
+    }
+
+    if (auto correction = corrections.claimUniqueCorrection()) {
+      auto diagnostic = emitDiagnostic(
+          anchor->getLoc(), diag::could_not_find_type_member_corrected,
+          instanceTy, Name, correction->CorrectedName);
+      diagnostic.highlight(baseExpr->getSourceRange())
+          .highlight(nameLoc.getSourceRange());
+      correction->addFixits(diagnostic);
+    } else {
+      emitBasicError(baseType);
+    }
+  } else if (auto moduleTy = baseType->getAs<ModuleType>()) {
+    emitDiagnostic(baseExpr->getLoc(), diag::no_member_of_module,
+                   moduleTy->getModule()->getName(), Name)
+        .highlight(baseExpr->getSourceRange())
+        .highlight(nameLoc.getSourceRange());
+    return true;
+  } else {
+    // Check for a few common cases that can cause missing members.
+    auto *ED = baseType->getEnumOrBoundGenericEnum();
+    if (ED && Name.isSimpleName("rawValue")) {
+      auto loc = ED->getNameLoc();
+      if (loc.isValid()) {
+        emitBasicError(baseType);
+        emitDiagnostic(loc, diag::did_you_mean_raw_type);
+        return true;
+      }
+    } else if (baseType->isAny()) {
+      emitBasicError(baseType);
+      emitDiagnostic(anchor->getLoc(), diag::any_as_anyobject_fixit)
+          .fixItInsert(baseExpr->getStartLoc(), "(")
+          .fixItInsertAfter(baseExpr->getEndLoc(), " as AnyObject)");
+      return true;
+    }
+
+    tryTypoCorrection();
+
+    if (auto correction = corrections.claimUniqueCorrection()) {
+      auto diagnostic = emitDiagnostic(
+          anchor->getLoc(), diag::could_not_find_value_member_corrected,
+          baseType, Name, correction->CorrectedName);
+      diagnostic.highlight(baseExpr->getSourceRange())
+          .highlight(nameLoc.getSourceRange());
+      correction->addFixits(diagnostic);
+    } else {
+      emitBasicError(baseType);
+    }
+  }
+
+  // Note all the correction candidates.
+  corrections.noteAllCandidates();
+  return true;
+}

lib/Sema/CSDiagnostics.h

@@ -23,6 +23,7 @@
 #include "swift/AST/Decl.h"
 #include "swift/AST/DiagnosticEngine.h"
 #include "swift/AST/Expr.h"
+#include "swift/AST/Identifier.h"
 #include "swift/AST/Types.h"
 #include "swift/Basic/SourceLoc.h"
 #include "llvm/ADT/ArrayRef.h"
@@ -646,6 +647,33 @@ class SubscriptMisuseFailure final : public FailureDiagnostic {
   bool diagnoseAsNote() override;
 };
 
+/// Diagnose situations when member referenced by name is missing
+/// from the associated base type, e.g.
+///
+/// ```swift
+/// struct S {}
+/// func foo(_ s: S) {
+///   let _: Int = s.foo(1, 2) // expected type is `(Int, Int) -> Int`
+/// }
+/// ```
+class MissingMemberFailure final : public FailureDiagnostic {
+  Type BaseType;
+  DeclName Name;
+
+public:
+  MissingMemberFailure(Expr *root, ConstraintSystem &cs, Type baseType,
+                       DeclName memberName, ConstraintLocator *locator)
+      : FailureDiagnostic(root, cs, locator), BaseType(baseType),
+        Name(memberName) {}
+
+  bool diagnoseAsError() override;
+
+private:
+  static DeclName findCorrectEnumCaseName(Type Ty,
+                                          TypoCorrectionResults &corrections,
+                                          DeclName memberName);
+};
+
 } // end namespace constraints
 } // end namespace swift