Fix "warning: fallthrough annotation does not directly precede switch label" in lambdas.

[alexfh]

Summary

This patch fixes http://llvm.org/PR17864 - "warning: fallthrough annotation does not directly precede switch label" in lambdas.

[alexfh]

Removed debugging code.

[rnk]

test/SemaCXX/switch-implicit-fallthrough.cpp

285

Why did this code have to move? Aaron asked about it.

[alexfh]

test/SemaCXX/switch-implicit-fallthrough.cpp

285

I've already answered on the list.

Clang seems to stop producing warnings after the function containing errors, so the test with errors should be the last one (or maybe even in a separate file).

[rsmith]

LGTM

If blocks also need a fix, feel free to do that in a later patch :)

lib/Sema/AnalysisBasedWarnings.cpp

bool VisitSwitchStmt(SwitchStmt *S) {
       FoundSwitchStatements = true;
       return true;
     }
 
     // We don't want to traverse local type declarations. We analyze their
     // methods separately.
     bool TraverseDecl(Decl *D) { return true; }
 
+    // We analyze lambda bodies separately. Skip them here.
+    bool TraverseLambdaBody(LambdaExpr *LE) { return true; }
+
   private:
 
     static const AttributedStmt *asFallThroughAttr(const Stmt *S) {
       if (const AttributedStmt *AS = dyn_cast_or_null<AttributedStmt>(S)) {
         if (hasSpecificAttr<FallThroughAttr>(AS->getAttrs()))
           return AS;
       }
       return nullptr;

test/SemaCXX/switch-implicit-fallthrough.cpp

case Value1:
       break;
     case Value2:
       n += 21;
       break;
   }
   return n;
 }
 
-int fallthrough_targets(int n) {
-  [[clang::fallthrough]]; // expected-error{{fallthrough annotation is outside switch statement}}
-
-  [[clang::fallthrough]]  // expected-error{{fallthrough attribute is only allowed on empty statements}}
-  switch (n) {
-    case 121:
-      n += 400;
-      [[clang::fallthrough]]; // no warning here, correct target
-    case 123:
-      [[clang::fallthrough]]  // expected-error{{fallthrough attribute is only allowed on empty statements}}
-      n += 800;
-      break;
-    [[clang::fallthrough]]    // expected-error{{fallthrough attribute is only allowed on empty statements}} expected-note{{did you forget ';'?}}
-    case 125:
-      n += 1600;
-  }
-  return n;
-}
-
 // Fallthrough annotations in local classes used to generate "fallthrough
 // annotation does not directly precede switch label" warning.
 void fallthrough_in_local_class() {
   class C {
     void f(int x) {
       switch (x) {
         case 0:
           x++;
           [[clang::fallthrough]]; // no diagnostics
         case 1:
           x++;
+        default: // \
+            expected-warning{{unannotated fall-through between switch labels}} \
+            expected-note{{insert 'break;' to avoid fall-through}}
           break;
       }
     }
   };
 }
 
+// Fallthrough annotations in lambdas used to generate "fallthrough
+// annotation does not directly precede switch label" warning.
+void fallthrough_in_lambda() {
+  (void)[] {
+    int x = 0;
+    switch (x) {
+    case 0:
+      x++;
+      [[clang::fallthrough]]; // no diagnostics
+    case 1:
+      x++;
+    default: // \
+        expected-warning{{unannotated fall-through between switch labels}} \
+        expected-note{{insert 'break;' to avoid fall-through}}
+      break;
+    }
+  };
+}
+
 namespace PR18983 {
   void fatal() __attribute__((noreturn));
   int num();
   void test() {
     switch (num()) {
     case 1:
       fatal();
       // Don't issue a warning.
     case 2:
       break;
     }
   }
 }
+
+int fallthrough_targets(int n) {
+  [[clang::fallthrough]]; // expected-error{{fallthrough annotation is outside switch statement}}
+
+  [[clang::fallthrough]]  // expected-error{{fallthrough attribute is only allowed on empty statements}}
+  switch (n) {
+    case 121:
+      n += 400;
+      [[clang::fallthrough]]; // no warning here, correct target
+    case 123:
+      [[clang::fallthrough]]  // expected-error{{fallthrough attribute is only allowed on empty statements}}
+      n += 800;
+      break;
+    [[clang::fallthrough]]    // expected-error{{fallthrough attribute is only allowed on empty statements}} expected-note{{did you forget ';'?}}
+    case 125:
+      n += 1600;
+  }
+  return n;
+}