Author: Haojian Wu Date: 2022-08-23T15:25:52+02:00 New Revision: f7dc91ad5609fab02cb805861dd232cab492340d
URL: https://github.com/llvm/llvm-project/commit/f7dc91ad5609fab02cb805861dd232cab492340d DIFF: https://github.com/llvm/llvm-project/commit/f7dc91ad5609fab02cb805861dd232cab492340d.diff LOG: [pseudo] Eliminate a false parse of structured binding declaration. Using the guard to implement part of the rule https://eel.is/c++draft/dcl.pre#6. ``` void foo() { // can be parsed as // - structured-binding declaration (a false parse) // - assignment expression array[index] = value; } ``` Differential Revision: https://reviews.llvm.org/D132260 Added: clang-tools-extra/pseudo/test/cxx/structured-binding.cpp Modified: clang-tools-extra/pseudo/lib/cxx/CXX.cpp clang-tools-extra/pseudo/lib/cxx/cxx.bnf Removed: ################################################################################ diff --git a/clang-tools-extra/pseudo/lib/cxx/CXX.cpp b/clang-tools-extra/pseudo/lib/cxx/CXX.cpp index 668c4d1bfcb6a..46d837aec44ad 100644 --- a/clang-tools-extra/pseudo/lib/cxx/CXX.cpp +++ b/clang-tools-extra/pseudo/lib/cxx/CXX.cpp @@ -161,6 +161,27 @@ bool guardNextTokenNotElse(const GuardParams &P) { return symbolToToken(P.Lookahead) != tok::kw_else; } +bool specifiesStructuredBinding(const GuardParams &P) { + const auto DSS = P.RHS[0]; + assert(DSS->symbol() == Symbol::decl_specifier_seq); + + auto Length = P.RHS[1]->startTokenIndex() - DSS->startTokenIndex(); + for (const auto &T : + P.Tokens.tokens().slice(DSS->startTokenIndex(), Length)) { + switch (T.Kind) { + case clang::tok::kw_static: + case clang::tok::kw_thread_local: + case clang::tok::kw_auto: + case clang::tok::kw_const: + case clang::tok::kw_volatile: + break; + default: + return false; + } + } + return true; +} + // Whether this e.g. decl-specifier contains an "exclusive" type such as a class // name, and thus can't combine with a second exclusive type. // @@ -320,6 +341,18 @@ llvm::DenseMap<ExtensionID, RuleGuard> buildGuards() { {rule::nested_name_specifier::COLONCOLON, TOKEN_GUARD(coloncolon, Tok.prev().Kind != tok::identifier)}, + // Implement C++ [dcl.pre#6]: + // A simple-declaration with an identifier-list is called a structured + // binding declaration ([dcl.struct.bind]). If the decl-specifier-seq + // contains any decl-specifier other than static, thread_local, auto, + // or cv-qualifiers, the program is ill-formed. + {rule::simple_declaration:: + decl_specifier_seq__ref_qualifier__L_SQUARE__identifier_list__R_SQUARE__initializer__SEMI, + specifiesStructuredBinding}, + {rule::simple_declaration:: + decl_specifier_seq__L_SQUARE__identifier_list__R_SQUARE__initializer__SEMI, + specifiesStructuredBinding}, + // The grammar distinguishes (only) user-defined vs plain string literals, // where the clang lexer distinguishes (only) encoding types. {rule::user_defined_string_literal_chunk::STRING_LITERAL, diff --git a/clang-tools-extra/pseudo/lib/cxx/cxx.bnf b/clang-tools-extra/pseudo/lib/cxx/cxx.bnf index 80c1b54437c07..36caf7b1e6337 100644 --- a/clang-tools-extra/pseudo/lib/cxx/cxx.bnf +++ b/clang-tools-extra/pseudo/lib/cxx/cxx.bnf @@ -330,7 +330,7 @@ block-declaration := opaque-enum-declaration nodeclspec-function-declaration := function-declarator ; alias-declaration := USING IDENTIFIER = defining-type-id ; simple-declaration := decl-specifier-seq init-declarator-list_opt ; -simple-declaration := decl-specifier-seq ref-qualifier_opt [ identifier-list ] initializer ; +simple-declaration := decl-specifier-seq ref-qualifier_opt [ identifier-list ] initializer ; [guard] static_assert-declaration := STATIC_ASSERT ( constant-expression ) ; static_assert-declaration := STATIC_ASSERT ( constant-expression , string-literal ) ; empty-declaration := ; diff --git a/clang-tools-extra/pseudo/test/cxx/structured-binding.cpp b/clang-tools-extra/pseudo/test/cxx/structured-binding.cpp new file mode 100644 index 0000000000000..1c68e928ddd62 --- /dev/null +++ b/clang-tools-extra/pseudo/test/cxx/structured-binding.cpp @@ -0,0 +1,6 @@ +// RUN: clang-pseudo -grammar=cxx -source=%s --start-symbol=statement-seq --print-forest | FileCheck %s + +// Verify there is no false parse of the structured binding declaration. +ABC[post] = abc; +// CHECK: statement-seq~expression-statement := expression ; +// CHECK: postfix-expression [ expr-or-braced-init-list ] _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
