[incrParse] Allow whitespaces to be reparsed in test

This greatly improves the ergonomics of writing tests and outweighs the
ability to test which whitespaces get parsed since their parsing
overhead should be minimal.

Author: ahoppen

test/incrParse/simple.swift

@@ -10,9 +10,9 @@
 // RUN: %incparse-test %s --test-case MULTI_EDIT_SAME_LINE
 
 func foo() {
-}<reparse REPLACE>
+}
 
-_ = <<REPLACE<6|||7>>></reparse REPLACE>
+<reparse REPLACE>_ = <<REPLACE<6|||7>>></reparse REPLACE>
 _ = <<REPLACE_BY_LONGER<6|||"Hello World">>>
 _ = <<REPLACE_BY_SHORTER<"Hello again"|||"a">>>
 <<INSERT<|||foo()>>>

tools/swift-syntax-test/swift-syntax-test.cpp

@@ -509,9 +509,19 @@ bool verifyReusedRegions(ByteBasedSourceRangeSet ExpectedReparseRegions,
   bool NoUnexpectedParse = true;
 
   for (auto ReparseRegion : UnexpectedReparseRegions.Ranges) {
-    NoUnexpectedParse = false;
     auto ReparseRange = ReparseRegion.toSourceRange(SourceMgr, BufferID);
 
+    // To improve the ergonomics when writing tests we do not want to complain
+    // about reparsed whitespaces.
+    auto RangeStr =
+        CharSourceRange(SourceMgr, ReparseRange.Start, ReparseRange.End).str();
+    llvm::Regex WhitespaceOnlyRegex("^\\s*$", llvm::Regex::Newline);
+    if (WhitespaceOnlyRegex.match(RangeStr)) {
+      continue;
+    }
+
+    NoUnexpectedParse = false;
+
     llvm::errs() << "\nERROR: Unexpectedly reparsed following region:\n";
     ReparseRange.print(llvm::errs(), SourceMgr);
   }