[libTooling] Further simplify `Stencil` type and introduce `MatchComputation`.

Summary:
This revision introduces a new interface `MatchComputation` which generalizes
the `Stencil` interface and replaces the `std::function` interface of
`MatchConsumer`. With this revision, `Stencil` (as an abstraction) becomes just
one collection of implementations of
`MatchComputation<std::string>`. Correspondingly, we remove the `Stencil` class
entirely in favor of a simple type alias, deprecate `MatchConsumer` and change
all functions that accepted `MatchConsumer<std::string>` to use
`MatchComputation<std::string>` instead.

Reviewers: gribozavr

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D69802

1 files changed, 9 insertions, 6 deletions

diff --git a/clang/unittests/Tooling/TransformerTest.cpp b/clang/unittests/Tooling/TransformerTest.cpp
index c99bf97..c382783 100644
--- a/clang/unittests/Tooling/TransformerTest.cpp
+++ b/clang/unittests/Tooling/TransformerTest.cpp
@@ -575,13 +575,16 @@ TEST_F(TransformerTest, TextGeneratorFailure) {
   std::string Input = "int conflictOneRule() { return 3 + 7; }";
   // Try to change the whole binary-operator expression AND one its operands:
   StringRef O = "O";
-  auto AlwaysFail = [](const ast_matchers::MatchFinder::MatchResult &)
-      -> llvm::Expected<std::string> {
-    return llvm::createStringError(llvm::errc::invalid_argument, "ERROR");
+  class AlwaysFail : public transformer::MatchComputation<std::string> {
+    llvm::Error eval(const ast_matchers::MatchFinder::MatchResult &,
+                     std::string *) const override {
+      return llvm::createStringError(llvm::errc::invalid_argument, "ERROR");
+    }
+    std::string toString() const override { return "AlwaysFail"; }
   };
-  Transformer T(
-      makeRule(binaryOperator().bind(O), changeTo(node(O), AlwaysFail)),
-      consumer());
+  Transformer T(makeRule(binaryOperator().bind(O),
+                         changeTo(node(O), std::make_shared<AlwaysFail>())),
+                consumer());
   T.registerMatchers(&MatchFinder);
   EXPECT_FALSE(rewrite(Input));
   EXPECT_THAT(Changes, IsEmpty());