[PATCH] D78848: [clangd] Disable delayed template parsing in the main file

[Sam McCall via Phabricator via cfe-commits]

sammccall created this revision.
sammccall added a reviewer: kadircet.
Herald added subscribers: cfe-commits, usaxena95, arphaman, jkorous, MaskRay, ilya-biryukov.
Herald added a project: clang.

This is on by default in windows and breaks most features in template bodies.
We'd already disabled it in code completion, now disable it for building ASTs.

Potential regressions:

- we may give spurious errors where files with templates relying on delayed parsing are directly opened
- we may misparse such template bodies that are instantiated (and therefore *were* previously parsed)

Still *probably* a win overall. Avoiding the regressions entirely would be
substantial work and we don't have plans for it now.

Fixes https://github.com/clangd/clangd/issues/302 (again)


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D78848

Files:
  clang-tools-extra/clangd/ParsedAST.cpp
  clang-tools-extra/clangd/unittests/ParsedASTTests.cpp


Index: clang-tools-extra/clangd/unittests/ParsedASTTests.cpp
===================================================================
--- clang-tools-extra/clangd/unittests/ParsedASTTests.cpp
+++ clang-tools-extra/clangd/unittests/ParsedASTTests.cpp
@@ -175,6 +175,17 @@
                         AllOf(DeclNamed("foo"), WithTemplateArgs("<bool>"))}));
 }
 
+TEST(ParsedASTTest, IgnoresDelayedTemplateParsing) {
+  auto TU = TestTU::withCode(R"cpp(
+    template <typename T> void xxx() {
+      int yyy = 0;
+    }
+  )cpp");
+  TU.ExtraArgs.push_back("-fdelayed-template-parsing");
+  auto AST = TU.build();
+  EXPECT_EQ(Decl::Var, findUnqualifiedDecl(AST, "yyy").getKind());
+}
+
 TEST(ParsedASTTest, TokensAfterPreamble) {
   TestTU TU;
   TU.AdditionalFiles["foo.h"] = R"(
Index: clang-tools-extra/clangd/ParsedAST.cpp
===================================================================
--- clang-tools-extra/clangd/ParsedAST.cpp
+++ clang-tools-extra/clangd/ParsedAST.cpp
@@ -256,6 +256,9 @@
   // Recovery expression currently only works for C++.
   if (CI->getLangOpts()->CPlusPlus)
     CI->getLangOpts()->RecoveryAST = Opts.BuildRecoveryAST;
+  // This is on-by-default in windows to allow parsing SDK headers, but it
+  // breaks many features. Disable it for the main-file (not preamble).
+  CI->getLangOpts()->DelayedTemplateParsing = false;
 
   StoreDiags ASTDiags;
   std::string Content = std::string(Buffer->getBuffer());


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