Fix a use-after-delete in ec59bf9 caught by ASan.

Author: jrose-apple

lib/Sema/MiscDiagnostics.cpp

@@ -19,6 +19,7 @@
 #include "swift/AST/ASTWalker.h"
 #include "swift/AST/NameLookup.h"
 #include "swift/AST/Pattern.h"
+#include "swift/Basic/Defer.h"
 #include "swift/Basic/SourceManager.h"
 #include "swift/Basic/StringExtras.h"
 #include "swift/Parse/Lexer.h"
@@ -827,6 +828,11 @@ bool swift::diagnoseArgumentLabelError(TypeChecker &TC, const Expr *expr,
 
   auto tuple = dyn_cast<TupleExpr>(expr);
   if (!tuple) {
+    llvm::SmallString<16> str;
+    // If the diagnostic is local, flush it before returning.
+    // This makes sure it's emitted before 'str' is destroyed.
+    defer { diagOpt.reset(); };
+
     if (newNames[0].empty()) {
       // This is probably a conversion from a value of labeled tuple type to
       // a scalar.
@@ -837,7 +843,6 @@ bool swift::diagnoseArgumentLabelError(TypeChecker &TC, const Expr *expr,
         if (scalarFieldIdx >= 0) {
           auto &field = tupleTy->getElement(scalarFieldIdx);
           if (field.hasName()) {
-            llvm::SmallString<16> str;
             str = ".";
             str += field.getName().str();
             if (!existingDiag) {
@@ -864,7 +869,6 @@ bool swift::diagnoseArgumentLabelError(TypeChecker &TC, const Expr *expr,
     if (auto parenExpr = dyn_cast<ParenExpr>(expr))
       expr = parenExpr->getSubExpr();
 
-    llvm::SmallString<16> str;
     str += newNames[0].str();
     str += ": ";
     if (!existingDiag) {
@@ -987,6 +991,9 @@ bool swift::diagnoseArgumentLabelError(TypeChecker &TC, const Expr *expr,
     diag.fixItReplace(tuple->getElementNameLocs()[i], newStr);
   }
 
+  // If the diagnostic is local, flush it before returning.
+  // This makes sure it's emitted before the message text buffers are destroyed.
+  diagOpt.reset();
   return true;
 }
 

lib/Sema/MiscDiagnostics.h

@@ -53,6 +53,8 @@ void fixItAccessibility(InFlightDiagnostic &diag, ValueDecl *VD,
 ///
 /// If \p existingDiag is null, the fix-its will be attached to an appropriate
 /// error diagnostic.
+///
+/// \returns true if the issue was diagnosed
 bool diagnoseArgumentLabelError(TypeChecker &TC, const Expr *expr,
                                 ArrayRef<Identifier> newNames,
                                 bool isSubscript,

test/attr/attr_availability.swift

@@ -284,6 +284,8 @@ func unavailableUnnamed(_ a: Int) {} // expected-note {{here}}
 func unavailableUnnamedSame(_ a: Int) {} // expected-note {{here}}
 @available(*, unavailable, renamed: "shinyLabeledArguments(_:)")
 func unavailableNewlyUnnamed(a: Int) {} // expected-note {{here}}
+@available(*, unavailable, renamed: "shinyLabeledArguments(veryLongNameToOverflowASmallStringABCDEFGHIJKLMNOPQRSTUVWXYZ:)")
+func unavailableVeryLongArgNames(a: Int) {} // expected-note {{here}}
 
 @available(*, unavailable, renamed: "shinyLabeledArguments(a:b:)")
 func unavailableMultiSame(a: Int, b: Int) {} // expected-note {{here}}
@@ -310,6 +312,7 @@ func testArgNames() {
   unavailableUnnamed(0) // expected-error {{'unavailableUnnamed' has been renamed to 'shinyLabeledArguments(example:)'}} {{3-21=shinyLabeledArguments}} {{22-22=example: }}
   unavailableUnnamedSame(0) // expected-error {{'unavailableUnnamedSame' has been renamed to 'shinyLabeledArguments(_:)'}} {{3-25=shinyLabeledArguments}}
   unavailableNewlyUnnamed(a: 0) // expected-error {{'unavailableNewlyUnnamed(a:)' has been renamed to 'shinyLabeledArguments(_:)'}} {{3-26=shinyLabeledArguments}} {{27-30=}}
+  unavailableVeryLongArgNames(a: 0) // expected-error {{'unavailableVeryLongArgNames(a:)' has been renamed to 'shinyLabeledArguments(veryLongNameToOverflowASmallStringABCDEFGHIJKLMNOPQRSTUVWXYZ:)'}} {{3-30=shinyLabeledArguments}} {{31-32=veryLongNameToOverflowASmallStringABCDEFGHIJKLMNOPQRSTUVWXYZ}}
   unavailableMultiSame(a: 0, b: 1) // expected-error {{'unavailableMultiSame(a:b:)' has been renamed to 'shinyLabeledArguments(a:b:)'}} {{3-23=shinyLabeledArguments}}
   unavailableMultiUnnamed(0, 1) // expected-error {{'unavailableMultiUnnamed' has been renamed to 'shinyLabeledArguments(example:another:)'}} {{3-26=shinyLabeledArguments}} {{27-27=example: }} {{30-30=another: }}
   unavailableMultiUnnamedSame(0, 1) // expected-error {{'unavailableMultiUnnamedSame' has been renamed to 'shinyLabeledArguments(_:_:)'}} {{3-30=shinyLabeledArguments}}