[clang-format] Fixed edge-case with `Style.SpacesInSquareBrackets` with trailing bare `&` lambda capture

[mitchell-stellar]

Summary

Lambda captures allow for a lone & capture, so &] needs to be properly handled.

[MyDeveloperDay]

LGTM

clang/lib/Format/TokenAnnotator.cpp

if (Right.is(TT_InlineASMColon) && Left.is(tok::coloncolon))
       return false;
     if (Right.is(TT_DictLiteral))
       return Style.SpacesInContainerLiterals;
     if (Right.is(TT_AttributeColon))
       return false;
     return true;
   }
   if (Left.is(TT_UnaryOperator)) {
+    if (!Right.is(tok::l_paren)) {
       // The alternative operators for ~ and ! are "compl" and "not".
       // If they are used instead, we do not want to combine them with
       // the token to the right, unless that is a left paren.
-    if (!Right.is(tok::l_paren)) {
       if (Left.is(tok::exclaim) && Left.TokenText == "not")
         return true;
       if (Left.is(tok::tilde) && Left.TokenText == "compl")
         return true;
+      // Lambda captures allow for a lone &, so "&]" needs to be properly
+      // handled.
+      if (Left.is(tok::amp) && Right.is(tok::r_square))
+        return Style.SpacesInSquareBrackets;
     }
     return (Style.SpaceAfterLogicalNot && Left.is(tok::exclaim)) ||
            Right.is(TT_BinaryOperator);
   }
 
   // If the next token is a binary operator or a selector name, we have
   // incorrectly classified the parenthesis as a cast. FIXME: Detect correctly.
   if (Left.is(TT_CastRParen))

clang/unittests/Format/FormatTest.cpp

TEST_F(FormatTest, ConfigurableSpacesInSquareBrackets) {
   verifyFormat("std::unique_ptr<int[]> foo() {}", Spaces);
   verifyFormat("int i = a[ a ][ a ]->f();", Spaces);
   verifyFormat("int i = (*b)[ a ]->f();", Spaces);
   // Lambdas.
   verifyFormat("int c = []() -> int { return 2; }();\n", Spaces);
   verifyFormat("return [ i, args... ] {};", Spaces);
   verifyFormat("int foo = [ &bar ]() {};", Spaces);
   verifyFormat("int foo = [ = ]() {};", Spaces);
+  verifyFormat("int foo = [ & ]() {};", Spaces);
   verifyFormat("int foo = [ =, &bar ]() {};", Spaces);
   verifyFormat("int foo = [ &bar, = ]() {};", Spaces);
 }
 
 TEST_F(FormatTest, ConfigurableSpaceBeforeAssignmentOperators) {
   verifyFormat("int a = 5;");
   verifyFormat("a += 42;");
   verifyFormat("a or_eq 8;");