diff --git a/clang-tools-extra/clangd/ParsedAST.h b/clang-tools-extra/clangd/ParsedAST.h
--- a/clang-tools-extra/clangd/ParsedAST.h
+++ b/clang-tools-extra/clangd/ParsedAST.h
@@ -120,7 +120,8 @@
   ///   - Does not have spelled or expanded tokens for files from preamble.
   syntax::TokenBuffer Tokens;
 
-  /// The start locations of all macro expansions spelled inside the main file.
+  /// The start locations of all macro definitions/expansions spelled **after**
+  /// preamble.
   /// Does not include expansions from inside other macro expansions.
   std::vector<SourceLocation> MainFileMacroExpLocs;
   // Data, stored after parsing.
diff --git a/clang-tools-extra/clangd/ParsedAST.cpp b/clang-tools-extra/clangd/ParsedAST.cpp
--- a/clang-tools-extra/clangd/ParsedAST.cpp
+++ b/clang-tools-extra/clangd/ParsedAST.cpp
@@ -98,23 +98,30 @@
   std::vector<Decl *> TopLevelDecls;
 };
 
-// This collects macro expansions in the main file.
+// This collects macro expansions/definitions in the main file.
 // (Contrast with CollectMainFileMacros in Preamble.cpp, which collects macro
 // *definitions* in the preamble region of the main file).
 class CollectMainFileMacroExpansions : public PPCallbacks {
   const SourceManager &SM;
   std::vector<SourceLocation> &MainFileMacroLocs;
 
+  void addLoc(SourceLocation Loc) {
+    if (!Loc.isMacroID() && isInsideMainFile(Loc, SM))
+      MainFileMacroLocs.push_back(Loc);
+  }
+
 public:
   CollectMainFileMacroExpansions(const SourceManager &SM,
                                  std::vector<SourceLocation> &MainFileMacroLocs)
       : SM(SM), MainFileMacroLocs(MainFileMacroLocs) {}
 
+  void MacroDefined(const Token &MacroNameTok,
+                    const MacroDirective *MD) override {
+    addLoc(MacroNameTok.getLocation());
+  }
   void MacroExpands(const Token &MacroNameTok, const MacroDefinition &MD,
                     SourceRange Range, const MacroArgs *Args) override {
-    SourceLocation L = MacroNameTok.getLocation();
-    if (!L.isMacroID() && isInsideMainFile(L, SM))
-      MainFileMacroLocs.push_back(L);
+    addLoc(MacroNameTok.getLocation());
   }
 };
 
diff --git a/clang-tools-extra/clangd/unittests/ParsedASTTests.cpp b/clang-tools-extra/clangd/unittests/ParsedASTTests.cpp
--- a/clang-tools-extra/clangd/unittests/ParsedASTTests.cpp
+++ b/clang-tools-extra/clangd/unittests/ParsedASTTests.cpp
@@ -229,32 +229,36 @@
 
 TEST(ParsedASTTest, CollectsMainFileMacroExpansions) {
   Annotations TestCase(R"cpp(
-    #define MACRO_ARGS(X, Y) X Y
+  // Preamble ends here.
+  namespace {
+    #define ^MACRO_ARGS(X, Y) X Y
     ^ID(int A);
     // Macro arguments included.
     ^MACRO_ARGS(^MACRO_ARGS(^MACRO_EXP(int), A), ^ID(= 2));
 
     // Macro names inside other macros not included.
-    #define FOO BAR
-    #define BAR 1
+    #define ^MACRO_ARGS2(X, Y) X Y
+    #define ^FOO BAR
+    #define ^BAR 1
     int A = ^FOO;
 
     // Macros from token concatenations not included.
-    #define CONCAT(X) X##A()
-    #define PREPEND(X) MACRO##X()
-    #define MACROA() 123
+    #define ^CONCAT(X) X##A()
+    #define ^PREPEND(X) MACRO##X()
+    #define ^MACROA() 123
     int B = ^CONCAT(MACRO);
     int D = ^PREPEND(A)
 
     // Macros included not from preamble not included.
     #include "foo.inc"
 
-    #define assert(COND) if (!(COND)) { printf("%s", #COND); exit(0); }
+    #define ^assert(COND) if (!(COND)) { printf("%s", #COND); exit(0); }
 
     void test() {
       // Includes macro expansions in arguments that are expressions
       ^assert(0 <= ^BAR);
     }
+  } // namespace
   )cpp");
   auto TU = TestTU::withCode(TestCase.code());
   TU.HeaderCode = R"cpp(
diff --git a/clang-tools-extra/clangd/unittests/SemanticHighlightingTests.cpp b/clang-tools-extra/clangd/unittests/SemanticHighlightingTests.cpp
--- a/clang-tools-extra/clangd/unittests/SemanticHighlightingTests.cpp
+++ b/clang-tools-extra/clangd/unittests/SemanticHighlightingTests.cpp
@@ -390,20 +390,22 @@
       // Tokens that share a source range but have conflicting Kinds are not
       // highlighted.
       R"cpp(
-      #define DEF_MULTIPLE(X) namespace X { class X { int X; }; }
-      #define DEF_CLASS(T) class T {};
+      // Preamble ends here.
+      namespace {
+      #define $Macro[[DEF_MULTIPLE]](X) namespace X { class X { int X; }; }
+      #define $Macro[[DEF_CLASS]](T) class T {};
       $Macro[[DEF_MULTIPLE]](XYZ);
       $Macro[[DEF_MULTIPLE]](XYZW);
       $Macro[[DEF_CLASS]]($Class[[A]])
-      #define MACRO_CONCAT(X, V, T) T foo##X = V
-      #define DEF_VAR(X, V) int X = V
-      #define DEF_VAR_T(T, X, V) T X = V
-      #define DEF_VAR_REV(V, X) DEF_VAR(X, V)
-      #define CPY(X) X
-      #define DEF_VAR_TYPE(X, Y) X Y
-      #define SOME_NAME variable
-      #define SOME_NAME_SET variable2 = 123
-      #define INC_VAR(X) X += 2
+      #define $Macro[[MACRO_CONCAT]](X, V, T) T foo##X = V
+      #define $Macro[[DEF_VAR]](X, V) int X = V
+      #define $Macro[[DEF_VAR_T]](T, X, V) T X = V
+      #define $Macro[[DEF_VAR_REV]](V, X) DEF_VAR(X, V)
+      #define $Macro[[CPY]](X) X
+      #define $Macro[[DEF_VAR_TYPE]](X, Y) X Y
+      #define $Macro[[SOME_NAME]] variable
+      #define $Macro[[SOME_NAME_SET]] variable2 = 123
+      #define $Macro[[INC_VAR]](X) X += 2
       $Primitive[[void]] $Function[[foo]]() {
         $Macro[[DEF_VAR]]($LocalVariable[[X]],  123);
         $Macro[[DEF_VAR_REV]](908, $LocalVariable[[XY]]);
@@ -422,15 +424,18 @@
       $Macro[[DEF_VAR]]($Variable[[XYZ]], 567);
       $Macro[[DEF_VAR_REV]](756, $Variable[[AB]]);
 
-      #define CALL_FN(F) F();
-      #define DEF_FN(F) void F ()
+      #define $Macro[[CALL_FN]](F) F();
+      #define $Macro[[DEF_FN]](F) void F ()
       $Macro[[DEF_FN]]($Function[[g]]) {
         $Macro[[CALL_FN]]($Function[[foo]]);
       }
+      } // namespace
     )cpp",
       R"cpp(
-      #define fail(expr) expr
-      #define assert(COND) if (!(COND)) { fail("assertion failed" #COND); }
+      // Preamble ends here.
+      namespace {
+      #define $Macro[[fail]](expr) expr
+      #define $Macro[[assert]](COND) if (!(COND)) { fail("assertion failed" #COND); }
       $Primitive[[int]] $Variable[[x]];
       $Primitive[[int]] $Variable[[y]];
       $Primitive[[int]] $Function[[f]]();
@@ -438,8 +443,9 @@
         $Macro[[assert]]($Variable[[x]] != $Variable[[y]]);
         $Macro[[assert]]($Variable[[x]] != $Function[[f]]());
       }
+      }
     )cpp",
-    R"cpp(
+      R"cpp(
       struct $Class[[S]] {
         $Primitive[[float]] $Field[[Value]];
         $Class[[S]] *$Field[[Next]];