1 files changed, 73 insertions, 0 deletions
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index b1fcd39a49a..dc20faf70c5 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -9877,6 +9877,79 @@ TEST_F(FormatTest, ConfigurableUseOfTab) {
                Tab);
 }
 
+TEST_F(FormatTest, ZeroTabWidth) {
+  FormatStyle Tab = getLLVMStyleWithColumns(42);
+  Tab.IndentWidth = 8;
+  Tab.UseTab = FormatStyle::UT_Never;
+  Tab.TabWidth = 0;
+  EXPECT_EQ("void a(){\n"
+            "    // line starts with '\t'\n"
+            "};",
+            format("void a(){\n"
+                   "\t// line starts with '\t'\n"
+                   "};",
+                   Tab));
+
+  EXPECT_EQ("void a(){\n"
+            "    // line starts with '\t'\n"
+            "};",
+            format("void a(){\n"
+                   "\t\t// line starts with '\t'\n"
+                   "};",
+                   Tab));
+
+  Tab.UseTab = FormatStyle::UT_ForIndentation;
+  EXPECT_EQ("void a(){\n"
+            "    // line starts with '\t'\n"
+            "};",
+            format("void a(){\n"
+                   "\t// line starts with '\t'\n"
+                   "};",
+                   Tab));
+
+  EXPECT_EQ("void a(){\n"
+            "    // line starts with '\t'\n"
+            "};",
+            format("void a(){\n"
+                   "\t\t// line starts with '\t'\n"
+                   "};",
+                   Tab));
+
+  Tab.UseTab = FormatStyle::UT_ForContinuationAndIndentation;
+  EXPECT_EQ("void a(){\n"
+            "    // line starts with '\t'\n"
+            "};",
+            format("void a(){\n"
+                   "\t// line starts with '\t'\n"
+                   "};",
+                   Tab));
+
+  EXPECT_EQ("void a(){\n"
+            "    // line starts with '\t'\n"
+            "};",
+            format("void a(){\n"
+                   "\t\t// line starts with '\t'\n"
+                   "};",
+                   Tab));
+
+  Tab.UseTab = FormatStyle::UT_Always;
+  EXPECT_EQ("void a(){\n"
+            "// line starts with '\t'\n"
+            "};",
+            format("void a(){\n"
+                   "\t// line starts with '\t'\n"
+                   "};",
+                   Tab));
+
+  EXPECT_EQ("void a(){\n"
+            "// line starts with '\t'\n"
+            "};",
+            format("void a(){\n"
+                   "\t\t// line starts with '\t'\n"
+                   "};",
+                   Tab));
+}
+
 TEST_F(FormatTest, CalculatesOriginalColumn) {
   EXPECT_EQ("\"qqqqqqqqqqqqqqqqqqqqqqqqqq\\\n"
             "q\"; /* some\n"