[clang-tidy] Extend readability-else-after-return to remove else after calls to [[noreturn]] functions (llvm#185202)

Closes llvm#184930.

Author: berkaysahiin

clang-tools-extra/clang-tidy/readability/ElseAfterReturnCheck.cpp

@@ -48,7 +48,7 @@ AST_MATCHER_P(Stmt, stripLabelLikeStatements,
 } // namespace
 
 static constexpr char InterruptingStr[] = "interrupting";
-static constexpr char WarningMessage[] = "do not use 'else' after '%0'";
+static constexpr char WarningMessage[] = "do not use 'else' after %0";
 static constexpr char WarnOnUnfixableStr[] = "WarnOnUnfixable";
 static constexpr char WarnOnConditionVariablesStr[] =
     "WarnOnConditionVariables";
@@ -174,7 +174,8 @@ void ElseAfterReturnCheck::registerPPCallbacks(const SourceManager &SM,
 void ElseAfterReturnCheck::registerMatchers(MatchFinder *Finder) {
   const auto InterruptsControlFlow = stmt(anyOf(
       returnStmt().bind(InterruptingStr), continueStmt().bind(InterruptingStr),
-      breakStmt().bind(InterruptingStr), cxxThrowExpr().bind(InterruptingStr)));
+      breakStmt().bind(InterruptingStr), cxxThrowExpr().bind(InterruptingStr),
+      callExpr(callee(functionDecl(isNoReturn()))).bind(InterruptingStr)));
 
   const auto IfWithInterruptingThenElse =
       ifStmt(unless(isConstexpr()), unless(isConsteval()),
@@ -231,13 +232,15 @@ static bool hasPreprocessorBranchEndBetweenLocations(
 
 static StringRef getControlFlowString(const Stmt &Stmt) {
   if (isa<ReturnStmt>(Stmt))
-    return "return";
+    return "'return'";
   if (isa<ContinueStmt>(Stmt))
-    return "continue";
+    return "'continue'";
   if (isa<BreakStmt>(Stmt))
-    return "break";
+    return "'break'";
   if (isa<CXXThrowExpr>(Stmt))
-    return "throw";
+    return "'throw'";
+  if (isa<CallExpr>(Stmt))
+    return "calling a function that doesn't return";
   llvm_unreachable("Unknown control flow interrupter");
 }
 

clang-tools-extra/docs/ReleaseNotes.rst

@@ -333,6 +333,9 @@ Changes in existing checks
   - Added support for handling attributed ``if`` then-branches such as
     ``[[likely]]`` and ``[[unlikely]]``.
 
+  - Diagnose and remove redundant ``else`` branches after calls to
+    ``[[noreturn]]`` functions.
+    
 - Improved :doc:`readability-enum-initial-value
   <clang-tidy/checks/readability/enum-initial-value>` check: the warning message
   now uses separate note diagnostics for each uninitialized enumerator, making

clang-tools-extra/test/clang-tidy/checkers/readability/else-after-return.cpp

@@ -438,3 +438,28 @@ void testLabels(bool b) {
       f(0);
   }
 }
+
+[[noreturn]] void noReturn();
+
+struct NoReturnMember {
+  [[noreturn]] void noReturn();
+};
+
+void testNoReturn() {
+  if (true) {
+    noReturn();
+  } else { // comment-28
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: do not use 'else' after calling a function that doesn't return
+    // CHECK-FIXES: {{^}}  } // comment-28
+    f(0);
+  }
+
+  if (true) {
+    NoReturnMember f;
+    f.noReturn();
+  } else { // comment-29
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: do not use 'else' after calling a function that doesn't return
+    // CHECK-FIXES: {{^}}  } // comment-29
+    f(0);
+  }
+}