[ASTImporter] Do not look up lambda classes

Summary:
Consider this code:
```
      void f() {
        auto L0 = [](){};
        auto L1 = [](){};
      }

```
First we import `L0` then `L1`. Currently we end up having only one
CXXRecordDecl for the two different lambdas. And that is a problem if
the body of their op() is different. This happens because when we import
`L1` then lookup finds the existing `L0` and since they are structurally
equivalent we just map the imported L0 to be the counterpart of L1.

We have the same problem in this case:
```
      template <typename F0, typename F1>
      void f(F0 L0 = [](){}, F1 L1 = [](){}) {}

```

In StructuralEquivalenceContext we could distinquish lambdas only by
their source location in these cases. But we the lambdas are actually
structrually equivalent they differn only by the source location.

Thus, the  solution is to disable lookup completely if the decl in
the "from" context is a lambda.
However, that could have other problems: what if the lambda is defined
in a header file and included in several TUs? I think we'd have as many
duplicates as many includes we have. I think we could live with that,
because the lambda classes are TU local anyway, we cannot just access
them from another TU.

Reviewers: a_sidorin, a.sidorin, shafik

Subscribers: rnkovacs, dkrupp, Szelethus, gamesh411, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D66348

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@370461 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/AST/ASTImporter.cpp b/lib/AST/ASTImporter.cpp
index 30ec1374ae4f6197ba6cb62e6abe64e82904db31..5ee9f760b6a2987d29d0abc5f6964988d8b9fa30 100644 (file)
--- a/lib/AST/ASTImporter.cpp
+++ b/lib/AST/ASTImporter.cpp
@@ -2633,7 +2633,7 @@ ExpectedDecl ASTNodeImporter::VisitRecordDecl(RecordDecl *D) {
 
   // We may already have a record of the same name; try to find and match it.
   RecordDecl *PrevDecl = nullptr;
-  if (!DC->isFunctionOrMethod()) {
+  if (!DC->isFunctionOrMethod() && !D->isLambda()) {
     SmallVector<NamedDecl *, 4> ConflictingDecls;
     auto FoundDecls =
         Importer.findDeclsInToCtx(DC, SearchName);

diff --git a/unittests/AST/ASTImporterTest.cpp b/unittests/AST/ASTImporterTest.cpp
index 2c27a4417f5c0d8a298e32e553cae75e1d13955f..cfee284e6875af89f7586e370b645336d78e698b 100644 (file)
--- a/unittests/AST/ASTImporterTest.cpp
+++ b/unittests/AST/ASTImporterTest.cpp
@@ -5644,6 +5644,117 @@ INSTANTIATE_TEST_CASE_P(ParameterizedTests, DeclContextTest,
 INSTANTIATE_TEST_CASE_P(ParameterizedTests, CanonicalRedeclChain,
                         ::testing::Values(ArgVector()), );
 
+TEST_P(ASTImporterOptionSpecificTestBase, LambdasAreDifferentiated) {
+  Decl *FromTU = getTuDecl(
+      R"(
+      void f() {
+        auto L0 = [](){};
+        auto L1 = [](){};
+      }
+      )",
+      Lang_CXX11, "input0.cc");
+  auto Pattern = lambdaExpr();
+  CXXRecordDecl *FromL0 =
+      FirstDeclMatcher<LambdaExpr>().match(FromTU, Pattern)->getLambdaClass();
+  CXXRecordDecl *FromL1 =
+      LastDeclMatcher<LambdaExpr>().match(FromTU, Pattern)->getLambdaClass();
+  ASSERT_NE(FromL0, FromL1);
+
+  CXXRecordDecl *ToL0 = Import(FromL0, Lang_CXX11);
+  CXXRecordDecl *ToL1 = Import(FromL1, Lang_CXX11);
+  EXPECT_NE(ToL0, ToL1);
+}
+
+TEST_P(ASTImporterOptionSpecificTestBase,
+       LambdasInFunctionParamsAreDifferentiated) {
+  Decl *FromTU = getTuDecl(
+      R"(
+      template <typename F0, typename F1>
+      void f(F0 L0 = [](){}, F1 L1 = [](){}) {}
+      )",
+      Lang_CXX11, "input0.cc");
+  auto Pattern = cxxRecordDecl(isLambda());
+  CXXRecordDecl *FromL0 =
+      FirstDeclMatcher<CXXRecordDecl>().match(FromTU, Pattern);
+  CXXRecordDecl *FromL1 =
+      LastDeclMatcher<CXXRecordDecl>().match(FromTU, Pattern);
+  ASSERT_NE(FromL0, FromL1);
+
+  CXXRecordDecl *ToL0 = Import(FromL0, Lang_CXX11);
+  CXXRecordDecl *ToL1 = Import(FromL1, Lang_CXX11);
+  ASSERT_NE(ToL0, ToL1);
+}
+
+TEST_P(ASTImporterOptionSpecificTestBase,
+       LambdasInFunctionParamsAreDifferentiatedWhenMacroIsUsed) {
+  Decl *FromTU = getTuDecl(
+      R"(
+      #define LAMBDA [](){}
+      template <typename F0, typename F1>
+      void f(F0 L0 = LAMBDA, F1 L1 = LAMBDA) {}
+      )",
+      Lang_CXX11, "input0.cc");
+  auto Pattern = cxxRecordDecl(isLambda());
+  CXXRecordDecl *FromL0 =
+      FirstDeclMatcher<CXXRecordDecl>().match(FromTU, Pattern);
+  CXXRecordDecl *FromL1 =
+      LastDeclMatcher<CXXRecordDecl>().match(FromTU, Pattern);
+  ASSERT_NE(FromL0, FromL1);
+
+  Import(FromL0, Lang_CXX11);
+  Import(FromL1, Lang_CXX11);
+  CXXRecordDecl *ToL0 = Import(FromL0, Lang_CXX11);
+  CXXRecordDecl *ToL1 = Import(FromL1, Lang_CXX11);
+  ASSERT_NE(ToL0, ToL1);
+}
+
+TEST_P(ASTImporterOptionSpecificTestBase, ImportAssignedLambda) {
+  Decl *FromTU = getTuDecl(
+      R"(
+      void f() {
+        auto x = []{} = {}; auto x2 = x;
+      }
+      )",
+      Lang_CXX2a, "input0.cc");
+  auto FromF = FirstDeclMatcher<FunctionDecl>().match(
+      FromTU, functionDecl(hasName("f")));
+  // We have only one lambda class.
+  ASSERT_EQ(
+      DeclCounter<CXXRecordDecl>().match(FromTU, cxxRecordDecl(isLambda())),
+      1u);
+
+  FunctionDecl *ToF = Import(FromF, Lang_CXX2a);
+  EXPECT_TRUE(ToF);
+  TranslationUnitDecl *ToTU = ToAST->getASTContext().getTranslationUnitDecl();
+  // We have only one lambda class after the import.
+  EXPECT_EQ(DeclCounter<CXXRecordDecl>().match(ToTU, cxxRecordDecl(isLambda())),
+            1u);
+}
+
+TEST_P(ASTImporterOptionSpecificTestBase, ImportDefaultConstructibleLambdas) {
+  Decl *FromTU = getTuDecl(
+      R"(
+      void f() {
+        auto x = []{} = {};
+        auto xb = []{} = {};
+      }
+      )",
+      Lang_CXX2a, "input0.cc");
+  auto FromF = FirstDeclMatcher<FunctionDecl>().match(
+      FromTU, functionDecl(hasName("f")));
+  // We have two lambda classes.
+  ASSERT_EQ(
+      DeclCounter<CXXRecordDecl>().match(FromTU, cxxRecordDecl(isLambda())),
+      2u);
+
+  FunctionDecl *ToF = Import(FromF, Lang_CXX2a);
+  EXPECT_TRUE(ToF);
+  TranslationUnitDecl *ToTU = ToAST->getASTContext().getTranslationUnitDecl();
+  // We have two lambda classes after the import.
+  EXPECT_EQ(DeclCounter<CXXRecordDecl>().match(ToTU, cxxRecordDecl(isLambda())),
+            2u);
+}
+
 INSTANTIATE_TEST_CASE_P(ParameterizedTests, ASTImporterLookupTableTest,
                         DefaultTestValuesForRunOptions, );