diff --git a/clang-tools-extra/clangd/unittests/ASTTests.cpp b/clang-tools-extra/clangd/unittests/ASTTests.cpp
--- a/clang-tools-extra/clangd/unittests/ASTTests.cpp
+++ b/clang-tools-extra/clangd/unittests/ASTTests.cpp
@@ -37,8 +37,6 @@
   for (Test T : Tests) {
     Annotations File(T.AnnotatedCode);
     auto AST = TestTU::withCode(File.code()).build();
-    ASSERT_TRUE(AST.getDiagnostics().empty())
-        << AST.getDiagnostics().begin()->Message;
     SourceManagerForFile SM("foo.cpp", File.code());
 
     for (Position Pos : File.points()) {
diff --git a/clang-tools-extra/clangd/unittests/CollectMacrosTests.cpp b/clang-tools-extra/clangd/unittests/CollectMacrosTests.cpp
--- a/clang-tools-extra/clangd/unittests/CollectMacrosTests.cpp
+++ b/clang-tools-extra/clangd/unittests/CollectMacrosTests.cpp
@@ -65,7 +65,7 @@
         #define $2[[PREPEND]](X) MACRO##X()
         #define $3[[MACROA]]() 123
         int B = $1[[CONCAT]](MACRO);
-        int D = $2[[PREPEND]](A)
+        int D = $2[[PREPEND]](A);
       )cpp",
       R"cpp(
         // FIXME: Macro names in a definition are not detected.
diff --git a/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp b/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp
--- a/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp
+++ b/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp
@@ -104,6 +104,7 @@
 TEST(DiagnosticsTest, DiagnosticRanges) {
   // Check we report correct ranges, including various edge-cases.
   Annotations Test(R"cpp(
+    // error-ok
     namespace test{};
     void $decl[[foo]]();
     class T{$explicit[[]]$constructor[[T]](int a);};
@@ -153,7 +154,7 @@
 }
 
 TEST(DiagnosticsTest, FlagsMatter) {
-  Annotations Test("[[void]] main() {}");
+  Annotations Test("[[void]] main() {} // error-ok");
   auto TU = TestTU::withCode(Test.code());
   EXPECT_THAT(TU.build().getDiagnostics(),
               ElementsAre(AllOf(Diag(Test.range(), "'main' must return 'int'"),
@@ -170,7 +171,7 @@
 
 TEST(DiagnosticsTest, DiagnosticPreamble) {
   Annotations Test(R"cpp(
-    #include $[["not-found.h"]]
+    #include $[["not-found.h"]] // error-ok
   )cpp");
 
   auto TU = TestTU::withCode(Test.code());
@@ -290,7 +291,7 @@
   Annotations Main(R"cpp(
     int main() {
       int i = 3;
-      double f = [[8]] / i;
+      double f = [[8]] / i; // error-ok
     }
   )cpp");
   TestTU TU = TestTU::withCode(Main.code());
@@ -309,6 +310,7 @@
   // We limit the size of printed code.
   Annotations Source(R"cpp(
     int main() {
+      // error-ok
       int somereallyreallyreallyreallyreallyreallyreallyreallylongidentifier;
       [[omereallyreallyreallyreallyreallyreallyreallyreallylongidentifier]]= 10;
     }
@@ -323,13 +325,14 @@
           "'somereallyreallyreallyreallyreallyreallyreallyreal…'"))));
   // Only show changes up to a first newline.
   Source = Annotations(R"cpp(
+    // error-ok
     int main() {
       int ident;
       [[ide\
-n]] = 10;
+n]] = 10; // error-ok
     }
   )cpp");
-  TU = TestTU::withCode(Source.code());
+  TU.Code = Source.code();
   EXPECT_THAT(TU.build().getDiagnostics(),
               ElementsAre(WithFix(
                   Fix(Source.range(), "ident", "change 'ide\\…' to 'ident'"))));
@@ -339,7 +342,7 @@
   Annotations Main(R"cpp(
     int main() {
       int i = 3;
-      double f = [[8]] / i;  // NOLINT
+      double f = [[8]] / i;  // NOLINT // error-ok
     }
   )cpp");
   TestTU TU = TestTU::withCode(Main.code());
@@ -363,7 +366,7 @@
   Annotations Test(R"cpp(
     #ifndef FOO
     #define FOO
-      int a = [[b]];
+      int a = [[b]]; // error-ok
     #else
       int x = y;
     #endif
@@ -379,7 +382,7 @@
     #define RET(x) return x + 10
 
     int* foo() {
-      RET($foo[[0]]);
+      RET($foo[[0]]); // error-ok
     }
     int* bar() {
       return $bar[[TEN]];
@@ -398,7 +401,7 @@
   Annotations Test(R"cpp(
     #define Define(name) void name() {}
 
-    [[Define]](main)
+    [[Define]](main) // error-ok
   )cpp");
   auto TU = TestTU::withCode(Test.code());
   EXPECT_THAT(TU.build().getDiagnostics(),
@@ -540,7 +543,7 @@
 }
 
 TEST(IncludeFixerTest, IncompleteType) {
-  Annotations Test(R"cpp(
+  Annotations Test(R"cpp(// error-ok
 $insert[[]]namespace ns {
   class X;
   $nested[[X::]]Nested n;
@@ -573,7 +576,7 @@
 }
 
 TEST(IncludeFixerTest, NoSuggestIncludeWhenNoDefinitionInHeader) {
-  Annotations Test(R"cpp(
+  Annotations Test(R"cpp(// error-ok
 $insert[[]]namespace ns {
   class X;
 }
@@ -604,7 +607,7 @@
 }
 
 TEST(IncludeFixerTest, Typo) {
-  Annotations Test(R"cpp(
+  Annotations Test(R"cpp(// error-ok
 $insert[[]]namespace ns {
 void foo() {
   $unqualified1[[X]] x;
@@ -648,7 +651,7 @@
 }
 
 TEST(IncludeFixerTest, MultipleMatchedSymbols) {
-  Annotations Test(R"cpp(
+  Annotations Test(R"cpp(// error-ok
 $insert[[]]namespace na {
 namespace nb {
 void foo() {
@@ -673,7 +676,7 @@
 }
 
 TEST(IncludeFixerTest, NoCrashMemebrAccess) {
-  Annotations Test(R"cpp(
+  Annotations Test(R"cpp(// error-ok
     struct X { int  xyz; };
     void g() { X x; x.$[[xy]] }
   )cpp");
@@ -690,7 +693,7 @@
 TEST(IncludeFixerTest, UseCachedIndexResults) {
   // As index results for the identical request are cached, more than 5 fixes
   // are generated.
-  Annotations Test(R"cpp(
+  Annotations Test(R"cpp(// error-ok
 $insert[[]]void foo() {
   $x1[[X]] x;
   $x2[[X]] x;
@@ -729,7 +732,7 @@
 }
 
 TEST(IncludeFixerTest, UnresolvedNameAsSpecifier) {
-  Annotations Test(R"cpp(
+  Annotations Test(R"cpp(// error-ok
 $insert[[]]namespace ns {
 }
 void g() {  ns::$[[scope]]::X_Y();  }
@@ -751,7 +754,7 @@
 }
 
 TEST(IncludeFixerTest, UnresolvedSpecifierWithSemaCorrection) {
-  Annotations Test(R"cpp(
+  Annotations Test(R"cpp(// error-ok
 $insert[[]]namespace clang {
 void f() {
   // "clangd::" will be corrected to "clang::" by Sema.
@@ -797,7 +800,7 @@
 }
 
 TEST(IncludeFixerTest, SpecifiedScopeIsNamespaceAlias) {
-  Annotations Test(R"cpp(
+  Annotations Test(R"cpp(// error-ok
 $insert[[]]namespace a {}
 namespace b = a;
 namespace c {
@@ -825,7 +828,7 @@
 
     struct A {
       Templ<char> s;
-      A() { [[a]]; } // this caused crashes if we compute scopes lazily.
+      A() { [[a]]; /*error-ok*/ } // crash if we compute scopes lazily.
     };
   )cpp");
 
@@ -841,7 +844,7 @@
   Annotations Main(R"cpp(
     #include [["a.h"]]
     void foo() {})cpp");
-  Annotations Header("[[no_type_spec]];");
+  Annotations Header("[[no_type_spec]]; // error-ok");
   TestTU TU = TestTU::withCode(Main.code());
   TU.AdditionalFiles = {{"a.h", Header.code()}};
   EXPECT_THAT(TU.build().getDiagnostics(),
@@ -856,7 +859,8 @@
     #include [["a.h"]]
     void foo() {})cpp");
   TestTU TU = TestTU::withCode(Main.code());
-  TU.AdditionalFiles = {{"a.h", "#include \"b.h\""}, {"b.h", "no_type_spec;"}};
+  TU.AdditionalFiles = {{"a.h", "#include \"b.h\""},
+                        {"b.h", "no_type_spec; // error-ok"}};
   EXPECT_THAT(TU.build().getDiagnostics(),
               UnorderedElementsAre(
                   Diag(Main.range(), "in included file: C++ requires a "
@@ -869,7 +873,8 @@
     #include $b[["b.h"]]
     void foo() {})cpp");
   TestTU TU = TestTU::withCode(Main.code());
-  TU.AdditionalFiles = {{"a.h", "no_type_spec;"}, {"b.h", "no_type_spec;"}};
+  TU.AdditionalFiles = {{"a.h", "no_type_spec; // error-ok"},
+                        {"b.h", "no_type_spec; // error-ok"}};
   EXPECT_THAT(TU.build().getDiagnostics(),
               UnorderedElementsAre(
                   Diag(Main.range("a"), "in included file: C++ requires a type "
@@ -884,8 +889,9 @@
     #include "b.h"
     void foo() {})cpp");
   TestTU TU = TestTU::withCode(Main.code());
-  TU.AdditionalFiles = {{"a.h", "#include \"b.h\"\n"},
-                        {"b.h", "#ifndef X\n#define X\nno_type_spec;\n#endif"}};
+  TU.AdditionalFiles = {
+      {"a.h", "#include \"b.h\"\n"},
+      {"b.h", "#ifndef X\n#define X\nno_type_spec; // error-ok\n#endif"}};
   EXPECT_THAT(TU.build().getDiagnostics(),
               UnorderedElementsAre(Diag(Main.range(),
                                         "in included file: C++ requires a type "
@@ -900,9 +906,10 @@
     #include [["b.h"]]
     void foo() {})cpp");
   TestTU TU = TestTU::withCode(Main.code());
-  TU.AdditionalFiles = {{"a.h", "#include \"c.h\"\n"},
-                        {"b.h", "#include \"c.h\"\n"},
-                        {"c.h", "#ifndef X\n#define X\nno_type_spec;\n#endif"}};
+  TU.AdditionalFiles = {
+      {"a.h", "#include \"c.h\"\n"},
+      {"b.h", "#include \"c.h\"\n"},
+      {"c.h", "#ifndef X\n#define X\nno_type_spec; // error-ok\n#endif"}};
   EXPECT_THAT(TU.build().getDiagnostics(),
               UnorderedElementsAre(
                   Diag(Main.range(), "in included file: C++ requires a "
@@ -920,7 +927,7 @@
                         {"c.h", R"cpp(
       #ifndef X
       #define X
-      no_type_spec_0;
+      no_type_spec_0; // error-ok
       no_type_spec_1;
       no_type_spec_2;
       no_type_spec_3;
@@ -943,7 +950,7 @@
     #include [["a.h"]]
     void foo() {})cpp");
   Annotations Header(R"cpp(
-    [[no_type_spec]];
+    [[no_type_spec]]; // error-ok
     int x = 5/0;)cpp");
   TestTU TU = TestTU::withCode(Main.code());
   TU.AdditionalFiles = {{"a.h", Header.code()}};
@@ -960,7 +967,7 @@
     void foo() {})cpp");
   Annotations Header(R"cpp(
     int x = 5/0;
-    int b = [[FOO]];)cpp");
+    int b = [[FOO]]; // error-ok)cpp");
   TestTU TU = TestTU::withCode(Main.code());
   TU.AdditionalFiles = {{"a.h", Header.code()}};
   TU.ExtraArgs = {"-DFOO=NOOO"};
@@ -974,7 +981,7 @@
 TEST(DiagsInHeaders, ErrorFromMacroExpansion) {
   Annotations Main(R"cpp(
   void bar() {
-    int fo;
+    int fo; // error-ok
     #include [["a.h"]]
   })cpp");
   Annotations Header(R"cpp(
@@ -991,7 +998,7 @@
 TEST(DiagsInHeaders, ErrorFromMacroArgument) {
   Annotations Main(R"cpp(
   void bar() {
-    int fo;
+    int fo; // error-ok
     #include [["a.h"]]
   })cpp");
   Annotations Header(R"cpp(
diff --git a/clang-tools-extra/clangd/unittests/FileIndexTests.cpp b/clang-tools-extra/clangd/unittests/FileIndexTests.cpp
--- a/clang-tools-extra/clangd/unittests/FileIndexTests.cpp
+++ b/clang-tools-extra/clangd/unittests/FileIndexTests.cpp
@@ -407,7 +407,6 @@
   TestTU TU;
   TU.HeaderCode = "class Foo{};";
   Annotations Main(R"cpp(
-    #include "foo.h"
     void f() {
       [[Foo]] foo;
     }
diff --git a/clang-tools-extra/clangd/unittests/FindTargetTests.cpp b/clang-tools-extra/clangd/unittests/FindTargetTests.cpp
--- a/clang-tools-extra/clangd/unittests/FindTargetTests.cpp
+++ b/clang-tools-extra/clangd/unittests/FindTargetTests.cpp
@@ -75,7 +75,6 @@
     auto TU = TestTU::withCode(A.code());
     TU.ExtraArgs = Flags;
     auto AST = TU.build();
-    EXPECT_THAT(AST.getDiagnostics(), ::testing::IsEmpty()) << Code;
     llvm::Annotations::Range R = A.range();
     SelectionTree Selection(AST.getASTContext(), AST.getTokens(), R.Begin,
                             R.End);
@@ -592,11 +591,6 @@
     TU.ExtraArgs.push_back("-std=c++2a");
 
     auto AST = TU.build();
-    for (auto &D : AST.getDiagnostics()) {
-      if (D.Severity > DiagnosticsEngine::Warning)
-        ADD_FAILURE() << D << Code;
-    }
-
     auto *TestDecl = &findDecl(AST, "foo");
     if (auto *T = llvm::dyn_cast<FunctionTemplateDecl>(TestDecl))
       TestDecl = T->getTemplatedDecl();
diff --git a/clang-tools-extra/clangd/unittests/HoverTests.cpp b/clang-tools-extra/clangd/unittests/HoverTests.cpp
--- a/clang-tools-extra/clangd/unittests/HoverTests.cpp
+++ b/clang-tools-extra/clangd/unittests/HoverTests.cpp
@@ -563,7 +563,6 @@
     TU.ExtraArgs.push_back("-std=c++17");
     TU.ExtraArgs.push_back("-fno-delayed-template-parsing");
     auto AST = TU.build();
-    ASSERT_TRUE(AST.getDiagnostics().empty());
 
     auto H = getHover(AST, T.point(), format::getLLVMStyle(), nullptr);
     ASSERT_TRUE(H);
@@ -630,8 +629,6 @@
     TestTU TU = TestTU::withCode(T.code());
     TU.ExtraArgs.push_back("-std=c++17");
     auto AST = TU.build();
-    ASSERT_TRUE(AST.getDiagnostics().empty());
-
     auto H = getHover(AST, T.point(), format::getLLVMStyle(), nullptr);
     ASSERT_FALSE(H);
   }
@@ -1589,9 +1586,6 @@
     TU.ExtraArgs.push_back("-std=c++17");
     TU.ExtraArgs.push_back("-Wno-gnu-designator");
     auto AST = TU.build();
-    for (const auto &D : AST.getDiagnostics())
-      ADD_FAILURE() << D;
-    ASSERT_TRUE(AST.getDiagnostics().empty());
 
     auto H = getHover(AST, T.point(), format::getLLVMStyle(), Index.get());
     ASSERT_TRUE(H);
@@ -1626,10 +1620,6 @@
 
   TestTU TU = TestTU::withCode(T.code());
   auto AST = TU.build();
-  for (const auto &D : AST.getDiagnostics())
-    ADD_FAILURE() << D;
-  ASSERT_TRUE(AST.getDiagnostics().empty());
-
   Symbol IndexSym;
   IndexSym.ID = *getSymbolID(&findDecl(AST, "X"));
   IndexSym.Documentation = "comment from index";
@@ -1663,10 +1653,6 @@
 
   TestTU TU = TestTU::withCode(T.code());
   auto AST = TU.build();
-  for (const auto &D : AST.getDiagnostics())
-    ADD_FAILURE() << D;
-  ASSERT_TRUE(AST.getDiagnostics().empty());
-
   for (const auto &P : T.points()) {
     auto H = getHover(AST, P, format::getLLVMStyle(), nullptr);
     ASSERT_TRUE(H);
@@ -1690,10 +1676,6 @@
 
   TestTU TU = TestTU::withCode(T.code());
   auto AST = TU.build();
-  for (const auto &D : AST.getDiagnostics())
-    ADD_FAILURE() << D;
-  ASSERT_TRUE(AST.getDiagnostics().empty());
-
   for (auto Comment : {"doc1", "doc2", "doc3"}) {
     for (const auto &P : T.points(Comment)) {
       auto H = getHover(AST, P, format::getLLVMStyle(), nullptr);
@@ -1866,9 +1848,6 @@
     Annotations T(C.Code);
     TestTU TU = TestTU::withCode(T.code());
     auto AST = TU.build();
-    for (const auto &D : AST.getDiagnostics())
-      ADD_FAILURE() << D;
-
     auto H = getHover(AST, T.point(), format::getLLVMStyle(), nullptr);
     ASSERT_TRUE(H);
     HoverInfo ExpectedHover;
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
@@ -173,6 +173,7 @@
       #include "foo.h"
       first_token;
       void test() {
+        // error-ok: invalid syntax, just examining token stream
       }
       last_token
 )cpp";
@@ -236,24 +237,26 @@
     // - preamble ends
     ^ID(int A);
     // Macro arguments included.
-    ^MACRO_ARGS(^MACRO_ARGS(^MACRO_EXP(int), A), ^ID(= 2));
+    ^MACRO_ARGS(^MACRO_ARGS(^MACRO_EXP(int), E), ^ID(= 2));
 
     // Macro names inside other macros not included.
     #define ^MACRO_ARGS2(X, Y) X Y
     #define ^FOO BAR
     #define ^BAR 1
-    int A = ^FOO;
+    int F = ^FOO;
 
     // Macros from token concatenations not included.
     #define ^CONCAT(X) X##A()
     #define ^PREPEND(X) MACRO##X()
     #define ^MACROA() 123
-    int B = ^CONCAT(MACRO);
-    int D = ^PREPEND(A)
+    int G = ^CONCAT(MACRO);
+    int H = ^PREPEND(A);
 
     // Macros included not from preamble not included.
     #include "foo.inc"
 
+    int printf(const char*, ...);
+    void exit(int);
     #define ^assert(COND) if (!(COND)) { printf("%s", #COND); exit(0); }
 
     void test() {
diff --git a/clang-tools-extra/clangd/unittests/PrintASTTests.cpp b/clang-tools-extra/clangd/unittests/PrintASTTests.cpp
--- a/clang-tools-extra/clangd/unittests/PrintASTTests.cpp
+++ b/clang-tools-extra/clangd/unittests/PrintASTTests.cpp
@@ -81,7 +81,7 @@
                                   template <template <class> class ...>
                                   class Aux {};
                                   template <> class ^Aux<Bar, Bar> {};
-                                  template <template <class> T>
+                                  template <template <class> class T>
                                   class ^Aux<T, T> {};)cpp",
                                 {"<Bar, Bar>", "<T, T>"}},
                             {
@@ -104,7 +104,7 @@
                                   template <>
                                   int ^S<double> = 0;)cpp",
                                 {"<T *>", "<double>"}},
-                        })),);
+                        })), );
 } // namespace
 } // namespace clangd
 } // namespace clang
diff --git a/clang-tools-extra/clangd/unittests/QualityTests.cpp b/clang-tools-extra/clangd/unittests/QualityTests.cpp
--- a/clang-tools-extra/clangd/unittests/QualityTests.cpp
+++ b/clang-tools-extra/clangd/unittests/QualityTests.cpp
@@ -112,7 +112,7 @@
   int deprecated() { return 0; }
 
   namespace { struct X { void y() { int z; } }; }
-  struct S{}
+  struct S{};
   )cpp";
   auto AST = Test.build();
 
diff --git a/clang-tools-extra/clangd/unittests/RenameTests.cpp b/clang-tools-extra/clangd/unittests/RenameTests.cpp
--- a/clang-tools-extra/clangd/unittests/RenameTests.cpp
+++ b/clang-tools-extra/clangd/unittests/RenameTests.cpp
@@ -294,7 +294,7 @@
       // Derived destructor explicit call.
       R"cpp(
         class [[Bas^e]] {};
-        class Derived : public [[Bas^e]] {}
+        class Derived : public [[Bas^e]] {};
 
         int main() {
           [[Bas^e]] *foo = new Derived();
diff --git a/clang-tools-extra/clangd/unittests/SelectionTests.cpp b/clang-tools-extra/clangd/unittests/SelectionTests.cpp
--- a/clang-tools-extra/clangd/unittests/SelectionTests.cpp
+++ b/clang-tools-extra/clangd/unittests/SelectionTests.cpp
@@ -259,7 +259,7 @@
       // Tricky case: CXXConstructExpr wants to claim the whole init range.
       {
           R"cpp(
-            class X { X(int); };
+            struct X { X(int); };
             class Y {
               X x;
               Y() : [[^x(4)]] {}
@@ -308,7 +308,7 @@
             };
             Str makeStr(const char*);
             void loop() {
-              for (const char* C : [[mak^eStr("foo"^)]])
+              for (const char C : [[mak^eStr("foo"^)]])
                 ;
             }
           )cpp",
@@ -484,7 +484,7 @@
   // (This is because we don't associate the stringified token with the arg).
   Case = R"cpp(
     void die(const char*);
-    #define assert(x) (x ? (void)0 : die(#x)
+    #define assert(x) (x ? (void)0 : die(#x))
     void foo() { assert(^42); }
   )cpp";
   Test = Annotations(Case);
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
@@ -271,7 +271,7 @@
       R"cpp(
       struct $Class[[AA]] {
         int $Field[[A]];
-      }
+      };
       int $Variable[[B]];
       $Class[[AA]] $Variable[[A]]{$Variable[[B]]};
     )cpp",
@@ -355,6 +355,7 @@
       };
       class $Class[[Foo]] {};
       class $Class[[Bar]] {
+      public:
         $Class[[Foo]] $Field[[Fo]];
         $Enum[[En]] $Field[[E]];
         int $Field[[I]];
@@ -432,6 +433,7 @@
         $Class[[G]]<$Class[[F]], &$Class[[F]]::$Method[[f]]> $LocalVariable[[GG]];
         $LocalVariable[[GG]].$Method[[foo]](&$LocalVariable[[FF]]);
         $Class[[A]]<$Function[[foo]]> $LocalVariable[[AA]];
+      }
     )cpp",
       // Tokens that share a source range but have conflicting Kinds are not
       // highlighted.
@@ -466,7 +468,7 @@
         $Macro[[INC_VAR]]($LocalVariable[[variable]]);
       }
       void $Macro[[SOME_NAME]]();
-      $Macro[[DEF_VAR]]($Variable[[XYZ]], 567);
+      $Macro[[DEF_VAR]]($Variable[[MMMMM]], 567);
       $Macro[[DEF_VAR_REV]](756, $Variable[[AB]]);
 
       #define $Macro[[CALL_FN]](F) F();
@@ -599,7 +601,7 @@
       struct $Class[[Foo]] {
         $Class[[Foo]]<$TemplateParameter[[TT]], $TemplateParameter[[TTs]]...>
           *$Field[[t]];
-      }
+      };
     )cpp",
       // Inactive code highlighting
       R"cpp(
@@ -673,7 +675,6 @@
     class $Class[[A]] {
       #include "imp.h"
     };
-    #endif
   )cpp",
                      {{"imp.h", R"cpp(
     int someMethod();
diff --git a/clang-tools-extra/clangd/unittests/SymbolInfoTests.cpp b/clang-tools-extra/clangd/unittests/SymbolInfoTests.cpp
--- a/clang-tools-extra/clangd/unittests/SymbolInfoTests.cpp
+++ b/clang-tools-extra/clangd/unittests/SymbolInfoTests.cpp
@@ -138,12 +138,15 @@
                                            "c:TestTU.cpp@38@F@bar#I#@aaa")}},
           {
               R"cpp( // Lambda capture
-          int ii;
-          auto lam = [ii]() {
-            return i^i;
-          };
+          void foo() {
+            int ii;
+            auto lam = [ii]() {
+              return i^i;
+            };
+          }
         )cpp",
-              {CreateExpectedSymbolDetails("ii", "", "c:@ii")}},
+              {CreateExpectedSymbolDetails("ii", "foo",
+                                           "c:TestTU.cpp@54@F@foo#@ii")}},
           {
               R"cpp( // Macro reference
           #define MACRO 5\nint i = MAC^RO;
diff --git a/clang-tools-extra/clangd/unittests/TestTU.h b/clang-tools-extra/clangd/unittests/TestTU.h
--- a/clang-tools-extra/clangd/unittests/TestTU.h
+++ b/clang-tools-extra/clangd/unittests/TestTU.h
@@ -64,6 +64,8 @@
   // Simulate a header guard of the header (using an #import directive).
   bool ImplicitHeaderGuard = true;
 
+  // By default, build() will report Error diagnostics as GTest errors.
+  // Suppress this behavior by adding an 'error-ok' comment to the code.
   ParsedAST build() const;
   SymbolSlab headerSymbols() const;
   std::unique_ptr<SymbolIndex> index() const;
diff --git a/clang-tools-extra/clangd/unittests/TestTU.cpp b/clang-tools-extra/clangd/unittests/TestTU.cpp
--- a/clang-tools-extra/clangd/unittests/TestTU.cpp
+++ b/clang-tools-extra/clangd/unittests/TestTU.cpp
@@ -13,6 +13,7 @@
 #include "index/FileIndex.h"
 #include "index/MemIndex.h"
 #include "clang/AST/RecursiveASTVisitor.h"
+#include "clang/Basic/Diagnostic.h"
 #include "clang/Frontend/CompilerInvocation.h"
 #include "clang/Frontend/Utils.h"
 
@@ -75,6 +76,22 @@
     ADD_FAILURE() << "Failed to build code:\n" << Code;
     llvm_unreachable("Failed to build TestTU!");
   }
+  // Check for error diagnostics and report gtest failures (unless expected).
+  // This guards against accidental syntax errors silently subverting tests.
+  // error-ok is awfully primitive - using clang -verify would be nicer.
+  // Ownership and layering makes it pretty hard.
+  if (llvm::none_of(Files, [](const auto &KV) {
+        return llvm::StringRef(KV.second).contains("error-ok");
+      })) {
+    for (const auto &D : AST->getDiagnostics())
+      if (D.Severity >= DiagnosticsEngine::Error) {
+        ADD_FAILURE()
+            << "TestTU failed to build (suppress with /*error-ok*/): \n"
+            << D << "\n\nFor code:\n"
+            << Code;
+        break; // Just report first error for simplicity.
+      }
+  }
   return std::move(*AST);
 }
 
diff --git a/clang-tools-extra/clangd/unittests/TweakTests.cpp b/clang-tools-extra/clangd/unittests/TweakTests.cpp
--- a/clang-tools-extra/clangd/unittests/TweakTests.cpp
+++ b/clang-tools-extra/clangd/unittests/TweakTests.cpp
@@ -76,26 +76,23 @@
 TWEAK_TEST(SwapIfBranches);
 TEST_F(SwapIfBranchesTest, Test) {
   Context = Function;
-  EXPECT_EQ(apply("^if (true) {return 100;} else {continue;}"),
-            "if (true) {continue;} else {return 100;}");
-  EXPECT_EQ(apply("^if () {return 100;} else {continue;}"),
-            "if () {continue;} else {return 100;}")
+  EXPECT_EQ(apply("^if (true) {return;} else {(void)0;}"),
+            "if (true) {(void)0;} else {return;}");
+  EXPECT_EQ(apply("^if (/*error-ok*/) {return;} else {(void)0;}"),
+            "if (/*error-ok*/) {(void)0;} else {return;}")
       << "broken condition";
-  EXPECT_AVAILABLE("^i^f^^(^t^r^u^e^) { return 100; } ^e^l^s^e^ { continue; }");
-  EXPECT_UNAVAILABLE("if (true) {^return ^100;^ } else { ^continue^;^ }");
+  EXPECT_AVAILABLE("^i^f^^(^t^r^u^e^) { return; } ^e^l^s^e^ { return; }");
+  EXPECT_UNAVAILABLE("if (true) {^return ^;^ } else { ^return^;^ }");
   // Available in subexpressions of the condition;
-  EXPECT_THAT("if(2 + [[2]] + 2) { return 2 + 2 + 2; } else {continue;}",
-              isAvailable());
+  EXPECT_THAT("if(2 + [[2]] + 2) { return; } else {return;}", isAvailable());
   // But not as part of the branches.
-  EXPECT_THAT("if(2 + 2 + 2) { return 2 + [[2]] + 2; } else { continue; }",
+  EXPECT_THAT("if(2 + 2 + 2) { [[return]]; } else { return; }",
               Not(isAvailable()));
   // Range covers the "else" token, so available.
-  EXPECT_THAT("if(2 + 2 + 2) { return 2 + [[2 + 2; } else {continue;]]}",
-              isAvailable());
+  EXPECT_THAT("if(2 + 2 + 2) { return[[; } else {return;]]}", isAvailable());
   // Not available in compound statements in condition.
-  EXPECT_THAT(
-      "if([]{return [[true]];}()) { return 2 + 2 + 2; } else { continue; }",
-      Not(isAvailable()));
+  EXPECT_THAT("if([]{return [[true]];}()) { return; } else { return; }",
+              Not(isAvailable()));
   // Not available if both sides aren't braced.
   EXPECT_THAT("^if (1) return; else { return; }", Not(isAvailable()));
   // Only one if statement is supported!
@@ -144,7 +141,7 @@
 TWEAK_TEST(DumpAST);
 TEST_F(DumpASTTest, Test) {
   EXPECT_AVAILABLE("^int f^oo() { re^turn 2 ^+ 2; }");
-  EXPECT_UNAVAILABLE("/*c^omment*/ int foo() return 2 ^ + 2; }");
+  EXPECT_UNAVAILABLE("/*c^omment*/ int foo() { return 2 ^ + 2; }");
   EXPECT_THAT(apply("int x = 2 ^+ 2;"),
               AllOf(StartsWith("message:"), HasSubstr("BinaryOperator"),
                     HasSubstr("'+'"), HasSubstr("|-IntegerLiteral"),
@@ -164,7 +161,7 @@
 TWEAK_TEST(ShowSelectionTree);
 TEST_F(ShowSelectionTreeTest, Test) {
   EXPECT_AVAILABLE("^int f^oo() { re^turn 2 ^+ 2; }");
-  EXPECT_AVAILABLE("/*c^omment*/ int foo() return 2 ^ + 2; }");
+  EXPECT_AVAILABLE("/*c^omment*/ int foo() { return 2 ^ + 2; }");
 
   const char *Output = R"(message:
  TranslationUnitDecl 
@@ -186,7 +183,7 @@
   EXPECT_THAT("template <typename T> struct ^X { T t; };", Not(isAvailable()));
   EXPECT_THAT("enum ^X {};", Not(isAvailable()));
 
-  EXPECT_THAT(apply("struct ^X { int x; int y; }"),
+  EXPECT_THAT(apply("struct ^X { int x; int y; };"),
               AllOf(StartsWith("message:"), HasSubstr("0 |   int x")));
 }
 
@@ -234,6 +231,7 @@
   EXPECT_AVAILABLE(AvailableCases);
 
   const char *NoCrashCases = R"cpp(
+    // error-ok: broken code, but shouldn't crash
     template<typename T, typename ...Args>
     struct Test<T, Args...> {
     Test(const T &v) :val[[(^]]) {}
@@ -269,7 +267,7 @@
       for(int a = 1, b = 2, c = 3; a > [[b + c]]; [[a++]])
         a = [[a + 1]];
       // lambda
-      auto lamb = [&[[a]], &[[b]]](int r = [[1]]) {return 1;}
+      auto lamb = [&[[a]], &[[b]]](int r = [[1]]) {return 1;};
       // assignment
       xyz([[a = 5]]);
       xyz([[a *= 5]]);
@@ -477,6 +475,7 @@
 TWEAK_TEST(ExpandMacro);
 TEST_F(ExpandMacroTest, Test) {
   Header = R"cpp(
+    // error-ok: not real c++, just token manipulation
     #define FOO 1 2 3
     #define FUNC(X) X+X+X
     #define EMPTY
@@ -513,7 +512,7 @@
     namespace ns {
       struct Class {
         struct Nested {};
-      }
+      };
       void Func();
     }
     inline namespace inl_ns {
@@ -536,7 +535,7 @@
   EXPECT_EQ(apply("namespace ns { void f() { ^auto C = Class(); } }"),
             "namespace ns { void f() { Class C = Class(); } }");
   // undefined functions should not be replaced
-  EXPECT_THAT(apply("au^to x = doesnt_exist();"),
+  EXPECT_THAT(apply("au^to x = doesnt_exist(); // error-ok"),
               StartsWith("fail: Could not deduce type for 'auto' type"));
   // function pointers should not be replaced
   EXPECT_THAT(apply("au^to x = &ns::Func;"),
@@ -551,8 +550,8 @@
   EXPECT_EQ(apply("namespace x { void y() { struct S{}; ^auto z = S(); } }"),
             "namespace x { void y() { struct S{}; S z = S(); } }");
   // replace array types
-  EXPECT_EQ(apply(R"cpp(au^to x = "test")cpp"),
-            R"cpp(const char * x = "test")cpp");
+  EXPECT_EQ(apply(R"cpp(au^to x = "test";)cpp"),
+            R"cpp(const char * x = "test";)cpp");
 
   EXPECT_UNAVAILABLE("dec^ltype(au^to) x = 10;");
 
@@ -977,7 +976,7 @@
   }]]
 
   // Definition with no body.
-  class Bar { Bar() = def^ault; }
+  class Bar { Bar() = def^ault; };
   )cpp");
 }
 
@@ -1213,9 +1212,7 @@
       public:
         void foo();
         int x;
-        static int y;
       };
-      Foo::y = 0;
 
       enum En { Zero, One };
       En x = Zero;
@@ -1229,9 +1226,7 @@
       public:
         void foo();
         int x;
-        static int y;
       };
-      Foo::y = 0;
 
       enum En { Zero, One };
       En x = Zero;
@@ -1682,11 +1677,11 @@
           namespace a { class Foo{}; }
           void foo();
           using namespace a;
-          void f^oo(){BODY})cpp",
+          void f^oo(){BODY();})cpp",
        R"cpp(
           #define BODY Foo
           namespace a { class Foo{}; }
-          void foo(){BODY}
+          void foo(){BODY();}
           using namespace a;
           )cpp"},
 
@@ -1899,13 +1894,13 @@
                                testPath("a.h"), "constexpr void foo(){}")));
 
   // Class members don't need "inline".
-  ExtraFiles["a.h"] = "struct Foo { void foo(); }";
+  ExtraFiles["a.h"] = "struct Foo { void foo(); };";
   apply(R"cpp(#include "a.h"
               void Foo::fo^o() {})cpp",
         &EditedFiles);
   EXPECT_THAT(EditedFiles,
               testing::ElementsAre(FileWithContents(
-                  testPath("a.h"), "struct Foo { void foo(){} }")));
+                  testPath("a.h"), "struct Foo { void foo(){} };")));
 
   // Function template doesn't need to be "inline"d.
   ExtraFiles["a.h"] = "template <typename T> void foo();";
@@ -1990,7 +1985,7 @@
   // out-of-line in such cases.
   EXPECT_UNAVAILABLE(R"cpp(
     template <typename> struct Foo { void fo^o(){} };
-    })cpp");
+    )cpp");
 }
 
 TEST_F(DefineOutlineTest, FailsWithoutSource) {
@@ -2134,14 +2129,14 @@
     llvm::StringRef ExpectedSource;
   } Cases[] = {
       {R"cpp(
-        namespace a { class Foo; }
+        namespace a { class Foo{}; }
         using namespace a;
-        Foo fo^o() { return; })cpp",
+        Foo fo^o() { return {}; })cpp",
        R"cpp(
-        namespace a { class Foo; }
+        namespace a { class Foo{}; }
         using namespace a;
         Foo foo() ;)cpp",
-       "a::Foo foo() { return; }"},
+       "a::Foo foo() { return {}; }"},
       {R"cpp(
         namespace a {
           class Foo {
@@ -2158,12 +2153,12 @@
         })cpp",
        "a::Foo::Bar a::Foo::foo() { return {}; }\n"},
       {R"cpp(
-        class Foo;
-        Foo fo^o() { return; })cpp",
+        class Foo {};
+        Foo fo^o() { return {}; })cpp",
        R"cpp(
-        class Foo;
+        class Foo {};
         Foo foo() ;)cpp",
-       "Foo foo() { return; }"},
+       "Foo foo() { return {}; }"},
   };
   llvm::StringMap<std::string> EditedFiles;
   for (auto &Case : Cases) {
diff --git a/clang-tools-extra/clangd/unittests/TypeHierarchyTests.cpp b/clang-tools-extra/clangd/unittests/TypeHierarchyTests.cpp
--- a/clang-tools-extra/clangd/unittests/TypeHierarchyTests.cpp
+++ b/clang-tools-extra/clangd/unittests/TypeHierarchyTests.cpp
@@ -71,8 +71,6 @@
   TestTU TU = TestTU::withCode(Source.code());
   auto AST = TU.build();
 
-  ASSERT_TRUE(AST.getDiagnostics().empty());
-
   for (Position Pt : Source.points()) {
     const CXXRecordDecl *RD = findRecordTypeAt(AST, Pt);
     EXPECT_EQ(&findDecl(AST, "Child2"), static_cast<const NamedDecl *>(RD));
@@ -95,8 +93,6 @@
   TestTU TU = TestTU::withCode(Source.code());
   auto AST = TU.build();
 
-  ASSERT_TRUE(AST.getDiagnostics().empty());
-
   for (Position Pt : Source.points()) {
     const CXXRecordDecl *RD = findRecordTypeAt(AST, Pt);
     EXPECT_EQ(&findDecl(AST, "Child2"), static_cast<const NamedDecl *>(RD));
@@ -118,8 +114,6 @@
   TestTU TU = TestTU::withCode(Source.code());
   auto AST = TU.build();
 
-  ASSERT_TRUE(AST.getDiagnostics().empty());
-
   for (Position Pt : Source.points()) {
     const CXXRecordDecl *RD = findRecordTypeAt(AST, Pt);
     // A field does not unambiguously specify a record type
@@ -147,8 +141,6 @@
   TestTU TU = TestTU::withCode(Source.code());
   auto AST = TU.build();
 
-  ASSERT_TRUE(AST.getDiagnostics().empty());
-
   const CXXRecordDecl *Parent =
       dyn_cast<CXXRecordDecl>(&findDecl(AST, "Parent"));
   const CXXRecordDecl *Child1 =
@@ -183,8 +175,6 @@
   TestTU TU = TestTU::withCode(Source.code());
   auto AST = TU.build();
 
-  ASSERT_TRUE(AST.getDiagnostics().empty());
-
   const CXXRecordDecl *Parent1 =
       dyn_cast<CXXRecordDecl>(&findDecl(AST, "Parent1"));
   const CXXRecordDecl *Parent2 =
@@ -210,8 +200,6 @@
   TestTU TU = TestTU::withCode(Source.code());
   auto AST = TU.build();
 
-  ASSERT_TRUE(AST.getDiagnostics().empty());
-
   const CXXRecordDecl *Parent =
       dyn_cast<CXXRecordDecl>(&findDecl(AST, "Parent"));
   const CXXRecordDecl *Child =
@@ -260,8 +248,6 @@
   TestTU TU = TestTU::withCode(Source.code());
   auto AST = TU.build();
 
-  ASSERT_TRUE(AST.getDiagnostics().empty());
-
   const CXXRecordDecl *Parent =
       dyn_cast<ClassTemplateDecl>(&findDecl(AST, "Parent"))->getTemplatedDecl();
   const CXXRecordDecl *ParentSpec =
@@ -289,8 +275,6 @@
   TestTU TU = TestTU::withCode(Source.code());
   auto AST = TU.build();
 
-  ASSERT_TRUE(AST.getDiagnostics().empty());
-
   const CXXRecordDecl *Parent =
       dyn_cast<CXXRecordDecl>(&findDecl(AST, "Parent"));
   const CXXRecordDecl *Child =
@@ -320,8 +304,6 @@
   TestTU TU = TestTU::withCode(Source.code());
   auto AST = TU.build();
 
-  ASSERT_TRUE(AST.getDiagnostics().empty());
-
   const CXXRecordDecl *Parent =
       dyn_cast<ClassTemplateDecl>(&findDecl(AST, "Parent"))->getTemplatedDecl();
   const CXXRecordDecl *Child1 =
@@ -397,7 +379,7 @@
   template <int N>
   struct $SDef[[S]] : S<N + 1> {};
 
-  S^<0> s;
+  S^<0> s; // error-ok
   )cpp");
 
   TestTU TU = TestTU::withCode(Source.code());
@@ -444,8 +426,6 @@
   TestTU TU = TestTU::withCode(Source.code());
   auto AST = TU.build();
 
-  ASSERT_TRUE(AST.getDiagnostics().empty());
-
   // Make sure getTypeHierarchy() doesn't get into an infinite recursion
   // for either a concrete starting point or a dependent starting point.
   llvm::Optional<TypeHierarchyItem> Result = getTypeHierarchy(
@@ -482,7 +462,6 @@
   TestTU TU = TestTU::withCode(Source.code());
   auto AST = TU.build();
   auto Index = TU.index();
-  ASSERT_TRUE(AST.getDiagnostics().empty());
 
   llvm::Optional<TypeHierarchyItem> Result = getTypeHierarchy(
       AST, Source.points()[0], 2, TypeHierarchyDirection::Children, Index.get(),
@@ -507,7 +486,6 @@
   TestTU TU = TestTU::withCode(Source.code());
   auto AST = TU.build();
   auto Index = TU.index();
-  ASSERT_TRUE(AST.getDiagnostics().empty());
 
   llvm::Optional<TypeHierarchyItem> Result = getTypeHierarchy(
       AST, Source.points()[0], 2, TypeHierarchyDirection::Children, Index.get(),
@@ -531,7 +509,6 @@
   TestTU TU = TestTU::withCode(Source.code());
   auto AST = TU.build();
   auto Index = TU.index();
-  ASSERT_TRUE(AST.getDiagnostics().empty());
 
   // FIXME: We'd like this to return the implicit specialization Child<int>,
   //        but currently libIndex does not expose relationships between
diff --git a/clang-tools-extra/clangd/unittests/XRefsTests.cpp b/clang-tools-extra/clangd/unittests/XRefsTests.cpp
--- a/clang-tools-extra/clangd/unittests/XRefsTests.cpp
+++ b/clang-tools-extra/clangd/unittests/XRefsTests.cpp
@@ -515,10 +515,6 @@
     TU.ExtraArgs.push_back("-fno-delayed-template-parsing");
 
     auto AST = TU.build();
-    for (auto &D : AST.getDiagnostics())
-      ADD_FAILURE() << D;
-    ASSERT_TRUE(AST.getDiagnostics().empty()) << Test;
-
     auto Results = locateSymbolAt(AST, T.point());
 
     if (!WantDecl) {
@@ -868,7 +864,7 @@
 
       R"cpp(// Forward declaration
         class [[Foo]];
-        class [[Foo]] {}
+        class [[Foo]] {};
         int main() {
           [[Fo^o]] foo;
         }
@@ -878,7 +874,7 @@
         int [[foo]](int) {}
         int main() {
           auto *X = &[[^foo]];
-          [[foo]](42)
+          [[foo]](42);
         }
       )cpp",
 
@@ -1182,8 +1178,6 @@
   for (const Case &C : Cases) {
     Annotations File(C.AnnotatedCode);
     auto AST = TestTU::withCode(File.code()).build();
-    ASSERT_TRUE(AST.getDiagnostics().empty())
-        << AST.getDiagnostics().begin()->Message;
     SourceLocation SL = llvm::cantFail(
         sourceLocationInMainFile(AST.getSourceManager(), File.point()));