clang-format: Add support for formatting (some) lambdas with explicit template parameters.

This patch makes cases work where the lambda's template list doesn't
contain any of + - ! ~ / % << | || && ^ == != >= <= ? : true false
(see added FIXME).

Ports r359967 to clang-format.

Differential Revision: https://reviews.llvm.org/D67246

llvm-svn: 371854

2 files changed, 22 insertions, 3 deletions

diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index 55ab654f960..9802711834e 100644
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -40,6 +40,21 @@ static bool canBeObjCSelectorComponent(const FormatToken &Tok) {
   return Tok.Tok.getIdentifierInfo() != nullptr;
 }
 
+/// With `Left` being '(', check if we're at either `[...](` or
+/// `[...]<...>(`, where the [ opens a lambda capture list.
+static bool isLambdaParameterList(const FormatToken *Left) {
+  // Skip <...> if present.
+  if (Left->Previous && Left->Previous->is(tok::greater) &&
+      Left->Previous->MatchingParen &&
+      Left->Previous->MatchingParen->is(TT_TemplateOpener))
+    Left = Left->Previous->MatchingParen;
+
+  // Check for `[...]`.
+  return Left->Previous && Left->Previous->is(tok::r_square) &&
+         Left->Previous->MatchingParen &&
+         Left->Previous->MatchingParen->is(TT_LambdaLSquare);
+}
+
 /// A parser that gathers additional information about tokens.
 ///
 /// The \c TokenAnnotator tries to match parenthesis and square brakets and
@@ -191,9 +206,7 @@ private:
                Left->Previous->is(TT_JsTypeColon)) {
       // let x: (SomeType);
       Contexts.back().IsExpression = false;
-    } else if (Left->Previous && Left->Previous->is(tok::r_square) &&
-               Left->Previous->MatchingParen &&
-               Left->Previous->MatchingParen->is(TT_LambdaLSquare)) {
+    } else if (isLambdaParameterList(Left)) {
       // This is a parameter list of a lambda expression.
       Contexts.back().IsExpression = false;
     } else if (Line.InPPDirective &&
diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index e552a055b04..8fd0e9433b6 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -1440,8 +1440,11 @@ bool UnwrappedLineParser::tryToParseLambda() {
     case tok::identifier:
     case tok::numeric_constant:
     case tok::coloncolon:
+    case tok::kw_class:
     case tok::kw_mutable:
     case tok::kw_noexcept:
+    case tok::kw_template:
+    case tok::kw_typename:
       nextToken();
       break;
     // Specialization of a template with an integer parameter can contain
@@ -1455,6 +1458,9 @@ bool UnwrappedLineParser::tryToParseLambda() {
     // followed by an `a->b` expression, such as:
     // ([obj func:arg] + a->b)
     // Otherwise the code below would parse as a lambda.
+    //
+    // FIXME: This heuristic is incorrect for C++20 generic lambdas with
+    // explicit template lists: []<bool b = true && false>(U &&u){}
     case tok::plus:
     case tok::minus:
     case tok::exclaim: