[clang-tools-extra] [clangd] Add a unit test suite for HeuristicResolver (PR #121313)

[Nathan Ridge via cfe-commits]

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+//===-- HeuristicResolverTests.cpp --------------------------*- C++ -*-----===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+#include "HeuristicResolver.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Tooling/Tooling.h"
+#include "gmock/gmock-matchers.h"
+#include "gtest/gtest.h"
+
+using namespace clang::ast_matchers;
+using clang::clangd::HeuristicResolver;
+using testing::ElementsAre;
+
+namespace clang {
+namespace {
+
+// Helper for matching a sequence of elements with a variadic list of matchers.
+// Usage: `ElementsAre(matchAdapter(Vs, MatchFunction)...)`, where `Vs...` is
+//        a variadic list of matchers.
+// For each `V` in `Vs`, this will match the corresponding element `E` if
+// `MatchFunction(V, E)` is true.
+MATCHER_P2(matchAdapter, MatcherForElement, MatchFunction, "matchAdapter") {
+  return MatchFunction(MatcherForElement, arg);
+}
+
+template <typename InputNode>
+using ResolveFnT = std::function<std::vector<const NamedDecl *>(
+    const HeuristicResolver *, const InputNode *)>;
+
+// Test heuristic resolution on `Code` using the resolution procedure
+// `ResolveFn`, which takes a `HeuristicResolver` and an input AST node of type
+// `InputNode` and returns a `std::vector<const NamedDecl *>`.
+// `InputMatcher` should be an AST matcher that matches a single node to pass as
+// input to `ResolveFn`, bound to the ID "input". `OutputMatchers` should be AST
+// matchers that each match a single node, bound to the ID "output".
+template <typename InputNode, typename InputMatcher, typename... OutputMatchers>
+void expectResolution(llvm::StringRef Code, ResolveFnT<InputNode> ResolveFn,
+                      const InputMatcher &IM, const OutputMatchers &...OMS) {
+  auto TU = tooling::buildASTFromCodeWithArgs(Code, {"-std=c++20"});
+  auto &Ctx = TU->getASTContext();
+  auto InputMatches = match(IM, Ctx);
+  ASSERT_EQ(1u, InputMatches.size());
+  const auto *Input = InputMatches[0].template getNodeAs<InputNode>("input");
+  ASSERT_TRUE(Input);
+
+  auto OutputNodeMatches = [&](auto &OutputMatcher, auto &Actual) {
+    auto OutputMatches = match(OutputMatcher, Ctx);
+    if (OutputMatches.size() != 1u)
+      return false;
+    const auto *ExpectedOutput =
+        OutputMatches[0].template getNodeAs<NamedDecl>("output");
+    if (!ExpectedOutput)
+      return false;
+    return ExpectedOutput == Actual;
+  };
+
+  HeuristicResolver H(Ctx);
+  auto Results = ResolveFn(&H, Input);
+  EXPECT_THAT(Results, ElementsAre(matchAdapter(OMS, OutputNodeMatches)...));
+}
+
+// Wrapper for the above that accepts a HeuristicResolver member function
+// pointer directly.
+template <typename InputNode, typename InputMatcher, typename... OutputMatchers>
+void expectResolution(llvm::StringRef Code,
+                      std::vector<const NamedDecl *> (
+                          HeuristicResolver::*ResolveFn)(const InputNode *)
+                          const,
+                      const InputMatcher &IM, const OutputMatchers &...OMS) {
+  expectResolution(Code, ResolveFnT<InputNode>(std::mem_fn(ResolveFn)), IM,
+                   OMS...);
+}
+
+TEST(HeuristicResolver, MemberExpr) {
+  std::string Code = R"cpp(
+    template <typename T>
+    struct S {
+      void bar() {}
+    };
+
+    template <typename T>
+    void foo(S<T> arg) {
+      arg.bar();
+    }
+  )cpp";
+  // Test resolution of "bar" in "arg.bar()".
+  expectResolution(Code, &HeuristicResolver::resolveMemberExpr,
+                   cxxDependentScopeMemberExpr().bind("input"),
----------------
HighCommander4 wrote:

Never mind, I _was_ overlooking something: there is a `hasMemberName()` matcher that works with `CXXDependentScopeMemberExpr`. I'll look at using that.

https://github.com/llvm/llvm-project/pull/121313