[clang-tools-extra] aacefc8 - [pseudo] Simplify/loosen the grammar around lambda captures.

[Sam McCall via cfe-commits]

Author: Sam McCall
Date: 2022-06-28T15:56:12+02:00
New Revision: aacefc817d9385835db5b5e30a21687ddb4f3f93

URL: https://github.com/llvm/llvm-project/commit/aacefc817d9385835db5b5e30a21687ddb4f3f93
DIFF: https://github.com/llvm/llvm-project/commit/aacefc817d9385835db5b5e30a21687ddb4f3f93.diff

LOG: [pseudo] Simplify/loosen the grammar around lambda captures.

Treat captures as a uniform list, rather than default-captures being special
snowflakes that may only appear at the start.

This accepts a larger set of (incorrect) code, and simplifies error-handling
by making this fit into the usual homogeneous-list pattern.

Differential Revision: https://reviews.llvm.org/D128708

Added: 
    clang-tools-extra/pseudo/test/cxx/capture-list.cpp

Modified: 
    clang-tools-extra/pseudo/lib/cxx.bnf

Removed: 
    


################################################################################
diff  --git a/clang-tools-extra/pseudo/lib/cxx.bnf b/clang-tools-extra/pseudo/lib/cxx.bnf
index aa243db6c5b40..d6f292d0ee246 100644
--- a/clang-tools-extra/pseudo/lib/cxx.bnf
+++ b/clang-tools-extra/pseudo/lib/cxx.bnf
@@ -76,17 +76,17 @@ nested-name-specifier := nested-name-specifier IDENTIFIER ::
 nested-name-specifier := nested-name-specifier TEMPLATE_opt simple-template-id ::
 lambda-expression := lambda-introducer lambda-declarator_opt compound-statement
 lambda-expression := lambda-introducer < template-parameter-list > requires-clause_opt lambda-declarator_opt compound-statement
-lambda-introducer := [ lambda-capture_opt ]
+#! We allow a capture-default to appear anywhere in a capture-list.
+# This simplifies the grammar and error recovery.
+lambda-introducer := [ capture-list_opt ]
 lambda-declarator := ( parameter-declaration-clause_opt ) decl-specifier-seq_opt noexcept-specifier_opt trailing-return-type_opt requires-clause_opt
-lambda-capture := capture-default
-lambda-capture := capture-list
-lambda-capture := capture-default , capture-list
-capture-default := &
-capture-default := =
 capture-list := capture
 capture-list := capture-list , capture
+capture := capture-default
 capture := simple-capture
 capture := init-capture
+capture-default := &
+capture-default := =
 simple-capture := IDENTIFIER ..._opt
 simple-capture := & IDENTIFIER ..._opt
 simple-capture := THIS

diff  --git a/clang-tools-extra/pseudo/test/cxx/capture-list.cpp b/clang-tools-extra/pseudo/test/cxx/capture-list.cpp
new file mode 100644
index 0000000000000..8659a6acae809
--- /dev/null
+++ b/clang-tools-extra/pseudo/test/cxx/capture-list.cpp
@@ -0,0 +1,23 @@
+// RUN: clang-pseudo -grammar=%cxx-bnf-file -source=%s --print-forest | FileCheck %s
+// We loosely allow capture defaults in any position/multiple times.
+auto lambda = [&, &foo, bar(x), =]{};
+// CHECK:      lambda-introducer := [ capture-list ]
+// CHECK-NEXT: ├─[
+// CHECK-NEXT: ├─capture-list
+// CHECK-NEXT: │ ├─capture-list
+// CHECK-NEXT: │ │ ├─capture-list
+// CHECK-NEXT: │ │ │ ├─capture-list~& := tok[4]
+// CHECK-NEXT: │ │ │ ├─,
+// CHECK-NEXT: │ │ │ └─capture~simple-capture
+// CHECK-NEXT: │ │ │   ├─&
+// CHECK-NEXT: │ │ │   └─IDENTIFIER := tok[7]
+// CHECK-NEXT: │ │ ├─,
+// CHECK-NEXT: │ │ └─capture~init-capture
+// CHECK-NEXT: │ │   ├─IDENTIFIER := tok[9]
+// CHECK-NEXT: │ │   └─initializer := ( expression-list )
+// CHECK-NEXT: │ │     ├─(
+// CHECK-NEXT: │ │     ├─expression-list~IDENTIFIER := tok[11]
+// CHECK-NEXT: │ │     └─)
+// CHECK-NEXT: │ ├─,
+// CHECK-NEXT: │ └─capture~=
+// CHECK-NEXT: └─]