[all-commits] [llvm/llvm-project] a0f4c1: [pseudo] Add error-recovery framework & brace-base...

[Sam McCall via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a0f4c10ae227a62c2a63611e64eba83f0ff0f577
      https://github.com/llvm/llvm-project/commit/a0f4c10ae227a62c2a63611e64eba83f0ff0f577
  Author: Sam McCall <sam.mccall at gmail.com>
  Date:   2022-06-28 (Tue, 28 Jun 2022)

  Changed paths:
    M clang-tools-extra/pseudo/include/clang-pseudo/GLR.h
    M clang-tools-extra/pseudo/include/clang-pseudo/grammar/Grammar.h
    M clang-tools-extra/pseudo/include/clang-pseudo/grammar/LRGraph.h
    M clang-tools-extra/pseudo/include/clang-pseudo/grammar/LRTable.h
    M clang-tools-extra/pseudo/lib/GLR.cpp
    M clang-tools-extra/pseudo/lib/grammar/Grammar.cpp
    M clang-tools-extra/pseudo/lib/grammar/GrammarBNF.cpp
    M clang-tools-extra/pseudo/lib/grammar/LRGraph.cpp
    M clang-tools-extra/pseudo/lib/grammar/LRTableBuild.cpp
    M clang-tools-extra/pseudo/test/cxx/empty-member-spec.cpp
    A clang-tools-extra/pseudo/test/cxx/recovery-init-list.cpp
    M clang-tools-extra/pseudo/unittests/GLRTest.cpp

  Log Message:
  -----------
  [pseudo] Add error-recovery framework & brace-based recovery

The idea is:
 - a parse failure is detected when all heads die when trying to shift
   the next token
 - we can recover by choosing a nonterminal we're partway through parsing,
   and determining where it ends through nonlocal means (e.g. matching brackets)
 - we can find candidates by walking up the stack from the (ex-)heads
 - the token range is defined using heuristics attached to grammar rules
 - the unparsed region is represented in the forest by an Opaque node

This patch has the core GLR functionality.
It does not allow recovery heuristics to be attached as extensions to
the grammar, but rather infers a brace-based heuristic.

Expected followups:
 - make recovery heuristics grammar extensions (depends on D127448)
 - add recover to our grammar for bracketed constructs and sequence nodes
 - change the structure of our augmented `_ := start` rules to eliminate
   some special-cases in glrParse.
 - (if I can work out how): avoid some spurious recovery cases described
   in comments
 - grammar changes to eliminate the hard distinction between init-list
   and designated-init-list shown in the recovery-init-list.cpp testcase

Differential Revision: https://reviews.llvm.org/D128486


  Commit: d25361c3afa6c3774c4f814a1142ceee9085db9e
      https://github.com/llvm/llvm-project/commit/d25361c3afa6c3774c4f814a1142ceee9085db9e
  Author: Sam McCall <sam.mccall at gmail.com>
  Date:   2022-06-28 (Tue, 28 Jun 2022)

  Changed paths:
    M clang-tools-extra/pseudo/lib/cxx/cxx.bnf

  Log Message:
  -----------
  [pseudo] Move ellipsis into initializer-list-item. NFC

This makes the list formation a bit simpler.


Compare: https://github.com/llvm/llvm-project/compare/79a2b4ba98a1...d25361c3afa6