[clang-format] Fix regression about short functions after #else

Summary:
This patch fixes a regression introduced in r312904, where the formatter confuses
the `else` in `#else` with an `else` of an `if-else` statement.
For example, formatting this code with google style
```
#ifdef A
int f() {}
#else
int f() {}
#endif
```
resulted in
```
#ifdef A
int f() {}
#else
int f() {
}
#endif
```

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D37973

llvm-svn: 314683

clang/lib/Format/UnwrappedLineFormatter.cpp

@@ -466,8 +466,7 @@ private:
     // Check that the current line allows merging. This depends on whether we
     // are in a control flow statements as well as several style flags.
     if (Line.First->isOneOf(tok::kw_else, tok::kw_case) ||
-        (Line.First->Next && Line.First->Next->is(tok::kw_else)) ||
-        (I != AnnotatedLines.begin() && I[-1]->Last->is(tok::kw_else)))
+        (Line.First->Next && Line.First->Next->is(tok::kw_else)))
       return 0;
     if (Line.First->isOneOf(tok::kw_if, tok::kw_while, tok::kw_do, tok::kw_try,
                             tok::kw___try, tok::kw_catch, tok::kw___finally,

clang/unittests/Format/FormatTest.cpp

@@ -7102,6 +7102,16 @@ TEST_F(FormatTest, SplitEmptyFunction) {
                "}",
                Style);
 }
+TEST_F(FormatTest, KeepShortFunctionAfterPPElse) {
+  FormatStyle Style = getLLVMStyle();
+  Style.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_All;
+  verifyFormat("#ifdef A\n"
+               "int f() {}\n"
+               "#else\n"
+               "int g() {}\n"
+               "#endif",
+               Style);
+}
 
 TEST_F(FormatTest, SplitEmptyClass) {
   FormatStyle Style = getLLVMStyle();