diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -74,6 +74,13 @@
                    : Line.Level * PPIndentWidth;
       Indent += AdditionalIndent;
     } else {
+      // When going to lower levels, forget previous higher levels so that we
+      // recompute future higher levels. But don't forget them if we enter a PP
+      // directive, since these do not terminate a C++ code block.
+      if (!Line.InPPDirective) {
+        assert(Line.Level <= IndentForLevel.size());
+        IndentForLevel.resize(Line.Level + 1);
+      }
       Indent = getIndent(Line.Level);
     }
     if (static_cast<int>(Indent) + Offset >= 0)
diff --git a/clang/unittests/Format/FormatTestSelective.cpp b/clang/unittests/Format/FormatTestSelective.cpp
--- a/clang/unittests/Format/FormatTestSelective.cpp
+++ b/clang/unittests/Format/FormatTestSelective.cpp
@@ -528,6 +528,26 @@
             format("  int a;\n"
                    "void ffffff() {}",
                    11, 0));
+
+  // https://github.com/llvm/llvm-project/issues/59178
+  Style = getMozillaStyle();
+  EXPECT_EQ("int a()\n"
+            "{\n"
+            "return 0;\n"
+            "}\n"
+            "int b()\n"
+            "{\n"
+            "  return 42;\n"
+            "}",
+            format("int a()\n"
+                   "{\n"
+                   "return 0;\n"
+                   "}\n"
+                   "int b()\n"
+                   "{\n"
+                   "return 42;\n" // Format this line only
+                   "}",
+                   32, 0));
 }
 
 TEST_F(FormatTestSelective, UnderstandsTabs) {
@@ -617,6 +637,70 @@
          "namespace ns1 { namespace ns2 {\n"
          "}}";
   EXPECT_EQ(Code, format(Code, 0, 0));
+
+  Style = getLLVMStyle();
+  Style.FixNamespaceComments = false;
+  Code = "namespace ns {\n"
+         "#define REF(alias) alias alias_var;\n"
+         "}";
+  EXPECT_EQ(Code, format(Code, 51, 1));
+}
+
+TEST_F(FormatTestSelective, FormatMacroRegardlessOfPreviousIndent) {
+  // clang-format currently does not (or should not) take into account the
+  // indent of previous unformatted lines when formatting a PP directive.
+  // Technically speaking, LevelIndentTracker::IndentForLevel is only for non-PP
+  // lines. So these tests here check that the indent of previous non-PP lines
+  // do not affect the formatting. If this requirement changes, the tests here
+  // need to be adapted.
+  Style = getLLVMStyle();
+
+  Style.IndentPPDirectives = FormatStyle::PPDirectiveIndentStyle::PPDIS_None;
+  EXPECT_EQ("      class Foo {\n"
+            "            void test() {\n"
+            "    #ifdef 1\n"
+            "#define some\n" // Formatted line
+            "#endif\n"       // That this line is also formatted might be a bug.
+            "            }};", // Ditto: Bug?
+            format("      class Foo {\n"
+                   "            void test() {\n"
+                   "    #ifdef 1\n"
+                   "                #define some\n" // format this line
+                   "         #endif\n"
+                   "    }};",
+                   75, 0));
+
+  Style.IndentPPDirectives =
+      FormatStyle::PPDirectiveIndentStyle::PPDIS_BeforeHash;
+  EXPECT_EQ("      class Foo {\n"
+            "            void test() {\n"
+            "    #ifdef 1\n"
+            "  #define some\n" // Formatted line
+            "         #endif\n"
+            "    }};",
+            format("      class Foo {\n"
+                   "            void test() {\n"
+                   "    #ifdef 1\n"
+                   "                #define some\n" // format this line
+                   "         #endif\n"
+                   "    }};",
+                   75, 0));
+
+  Style.IndentPPDirectives =
+      FormatStyle::PPDirectiveIndentStyle::PPDIS_AfterHash;
+  EXPECT_EQ("      class Foo {\n"
+            "            void test() {\n"
+            "    #ifdef 1\n"
+            "#  define some\n" // Formatted line
+            "#endif\n" // That this line is also formatted might be a bug.
+            "    }};",
+            format("      class Foo {\n"
+                   "            void test() {\n"
+                   "    #ifdef 1\n"
+                   "                #define some\n" // format this line
+                   "         #endif\n"
+                   "    }};",
+                   75, 0));
 }
 
 } // end namespace