[c++20] P0780R2: Support pack-expansion of init-captures.
This permits an init-capture to introduce a new pack:
template<typename ...T> auto x = [...a = T()] { /* a is a pack */ };
To support this, the mechanism for allowing ParmVarDecls to be packs has
been extended to support arbitrary local VarDecls.
llvm-svn: 361300
diff --git a/clang/lib/Parse/ParseExprCXX.cpp b/clang/lib/Parse/ParseExprCXX.cpp
index cb0fb72..6173a6c 100644
--- a/clang/lib/Parse/ParseExprCXX.cpp
+++ b/clang/lib/Parse/ParseExprCXX.cpp
@@ -20,7 +20,7 @@
#include "clang/Sema/ParsedTemplate.h"
#include "clang/Sema/Scope.h"
#include "llvm/Support/ErrorHandling.h"
-
+#include <numeric>
using namespace clang;
@@ -714,10 +714,10 @@
if (Next.is(tok::r_square) || // []
Next.is(tok::equal) || // [=
(Next.is(tok::amp) && // [&] or [&,
- (After.is(tok::r_square) ||
- After.is(tok::comma))) ||
+ After.isOneOf(tok::r_square, tok::comma)) ||
(Next.is(tok::identifier) && // [identifier]
- After.is(tok::r_square))) {
+ After.is(tok::r_square)) ||
+ Next.is(tok::ellipsis)) { // [...
return ParseLambdaExpression();
}
@@ -798,6 +798,15 @@
return true;
};
+ // Perform some irreversible action if this is a non-tentative parse;
+ // otherwise note that our actions were incomplete.
+ auto NonTentativeAction = [&](llvm::function_ref<void()> Action) {
+ if (Tentative)
+ *Tentative = LambdaIntroducerTentativeParse::Incomplete;
+ else
+ Action();
+ };
+
// Parse capture-default.
if (Tok.is(tok::amp) &&
(NextToken().is(tok::comma) || NextToken().is(tok::r_square))) {
@@ -857,7 +866,7 @@
LambdaCaptureInitKind InitKind = LambdaCaptureInitKind::NoInit;
SourceLocation Loc;
IdentifierInfo *Id = nullptr;
- SourceLocation EllipsisLoc;
+ SourceLocation EllipsisLocs[4];
ExprResult Init;
SourceLocation LocStart = Tok.getLocation();
@@ -875,6 +884,8 @@
Kind = LCK_This;
Loc = ConsumeToken();
} else {
+ TryConsumeToken(tok::ellipsis, EllipsisLocs[0]);
+
if (Tok.is(tok::amp)) {
Kind = LCK_ByRef;
ConsumeToken();
@@ -887,6 +898,8 @@
}
}
+ TryConsumeToken(tok::ellipsis, EllipsisLocs[1]);
+
if (Tok.is(tok::identifier)) {
Id = Tok.getIdentifierInfo();
Loc = ConsumeToken();
@@ -901,6 +914,8 @@
});
}
+ TryConsumeToken(tok::ellipsis, EllipsisLocs[2]);
+
if (Tok.is(tok::l_paren)) {
BalancedDelimiterTracker Parens(*this, tok::l_paren);
Parens.consumeOpen();
@@ -982,9 +997,9 @@
ConsumeAnnotationToken();
}
}
- } else {
- TryConsumeToken(tok::ellipsis, EllipsisLoc);
}
+
+ TryConsumeToken(tok::ellipsis, EllipsisLocs[3]);
}
// Check if this is a message send before we act on a possible init-capture.
@@ -995,60 +1010,81 @@
return false;
}
- // If this is an init capture, process the initialization expression
- // right away. For lambda init-captures such as the following:
- // const int x = 10;
- // auto L = [i = x+1](int a) {
- // return [j = x+2,
- // &k = x](char b) { };
- // };
- // keep in mind that each lambda init-capture has to have:
- // - its initialization expression executed in the context
- // of the enclosing/parent decl-context.
- // - but the variable itself has to be 'injected' into the
- // decl-context of its lambda's call-operator (which has
- // not yet been created).
- // Each init-expression is a full-expression that has to get
- // Sema-analyzed (for capturing etc.) before its lambda's
- // call-operator's decl-context, scope & scopeinfo are pushed on their
- // respective stacks. Thus if any variable is odr-used in the init-capture
- // it will correctly get captured in the enclosing lambda, if one exists.
- // The init-variables above are created later once the lambdascope and
- // call-operators decl-context is pushed onto its respective stack.
+ // Ensure that any ellipsis was in the right place.
+ SourceLocation EllipsisLoc;
+ if (std::any_of(std::begin(EllipsisLocs), std::end(EllipsisLocs),
+ [](SourceLocation Loc) { return Loc.isValid(); })) {
+ // The '...' should appear before the identifier in an init-capture, and
+ // after the identifier otherwise.
+ bool InitCapture = InitKind != LambdaCaptureInitKind::NoInit;
+ SourceLocation *ExpectedEllipsisLoc =
+ !InitCapture ? &EllipsisLocs[2] :
+ Kind == LCK_ByRef ? &EllipsisLocs[1] :
+ &EllipsisLocs[0];
+ EllipsisLoc = *ExpectedEllipsisLoc;
- // Since the lambda init-capture's initializer expression occurs in the
- // context of the enclosing function or lambda, therefore we can not wait
- // till a lambda scope has been pushed on before deciding whether the
- // variable needs to be captured. We also need to process all
- // lvalue-to-rvalue conversions and discarded-value conversions,
- // so that we can avoid capturing certain constant variables.
- // For e.g.,
- // void test() {
- // const int x = 10;
- // auto L = [&z = x](char a) { <-- don't capture by the current lambda
- // return [y = x](int i) { <-- don't capture by enclosing lambda
- // return y;
- // }
- // };
- // }
- // If x was not const, the second use would require 'L' to capture, and
- // that would be an error.
+ unsigned DiagID = 0;
+ if (EllipsisLoc.isInvalid()) {
+ DiagID = diag::err_lambda_capture_misplaced_ellipsis;
+ for (SourceLocation Loc : EllipsisLocs) {
+ if (Loc.isValid())
+ EllipsisLoc = Loc;
+ }
+ } else {
+ unsigned NumEllipses = std::accumulate(
+ std::begin(EllipsisLocs), std::end(EllipsisLocs), 0,
+ [](int N, SourceLocation Loc) { return N + Loc.isValid(); });
+ if (NumEllipses > 1)
+ DiagID = diag::err_lambda_capture_multiple_ellipses;
+ }
+ if (DiagID) {
+ NonTentativeAction([&] {
+ // Point the diagnostic at the first misplaced ellipsis.
+ SourceLocation DiagLoc;
+ for (SourceLocation &Loc : EllipsisLocs) {
+ if (&Loc != ExpectedEllipsisLoc && Loc.isValid()) {
+ DiagLoc = Loc;
+ break;
+ }
+ }
+ assert(DiagLoc.isValid() && "no location for diagnostic");
+ // Issue the diagnostic and produce fixits showing where the ellipsis
+ // should have been written.
+ auto &&D = Diag(DiagLoc, DiagID);
+ if (DiagID == diag::err_lambda_capture_misplaced_ellipsis) {
+ SourceLocation ExpectedLoc =
+ InitCapture ? Loc
+ : Lexer::getLocForEndOfToken(
+ Loc, 0, PP.getSourceManager(), getLangOpts());
+ D << InitCapture << FixItHint::CreateInsertion(ExpectedLoc, "...");
+ }
+ for (SourceLocation &Loc : EllipsisLocs) {
+ if (&Loc != ExpectedEllipsisLoc && Loc.isValid())
+ D << FixItHint::CreateRemoval(Loc);
+ }
+ });
+ }
+ }
+
+ // Process the init-capture initializers now rather than delaying until we
+ // form the lambda-expression so that they can be handled in the context
+ // enclosing the lambda-expression, rather than in the context of the
+ // lambda-expression itself.
ParsedType InitCaptureType;
- if (Tentative && Init.isUsable())
- *Tentative = LambdaIntroducerTentativeParse::Incomplete;
- else if (Init.isUsable()) {
+ if (Init.isUsable())
Init = Actions.CorrectDelayedTyposInExpr(Init.get());
- if (Init.isUsable()) {
+ if (Init.isUsable()) {
+ NonTentativeAction([&] {
// Get the pointer and store it in an lvalue, so we can use it as an
// out argument.
Expr *InitExpr = Init.get();
// This performs any lvalue-to-rvalue conversions if necessary, which
// can affect what gets captured in the containing decl-context.
InitCaptureType = Actions.actOnLambdaInitCaptureInitialization(
- Loc, Kind == LCK_ByRef, Id, InitKind, InitExpr);
+ Loc, Kind == LCK_ByRef, EllipsisLoc, Id, InitKind, InitExpr);
Init = InitExpr;
- }
+ });
}
SourceLocation LocEnd = PrevTokLocation;