SILGen: Generate valid SIL for no-op #_hasSymbol conditions.

Author: tshortli

lib/SILGen/SILGenDecl.cpp

@@ -1602,7 +1602,15 @@ void SILGenFunction::emitStmtCondition(StmtCondition Cond, JumpDest FalseDest,
 
     case StmtConditionElement::CK_HasSymbol: {
       auto info = elt.getHasSymbolInfo();
-      assert(!info->isInvalid());
+      if (info->isInvalid()) {
+        // This condition may have referenced a decl that isn't valid in some
+        // way but for developer convenience wasn't treated as an error. Just
+        // emit a 'true' condition value.
+        SILType i1 = SILType::getBuiltinIntegerType(1, getASTContext());
+        booleanTestValue = B.createIntegerLiteral(loc, i1, 1);
+        break;
+      }
+
       auto expr = info->getSymbolExpr();
       auto declRef = info->getReferencedDecl();
       assert(declRef);

test/SILGen/has_symbol.swift

@@ -263,3 +263,15 @@ func testMetatypes() {
 
 // --- E.self ---
 // CHECK: sil hidden_external @$s17has_symbol_helper1EOTwS : $@convention(thin) () -> Builtin.Int1
+
+// CHECK: sil hidden [ossa] @$s4test0A15NotWeaklyLinkedyyF : $@convention(thin) () -> ()
+func testNotWeaklyLinked() {
+  // `Swift.Int` is not weakly imported so this check is a no-op.
+
+  // CHECK: [[RES:%[0-9]+]] = integer_literal $Builtin.Int1, -1
+  // CHECK: cond_br [[RES]], bb{{[0-9]+}}, bb{{[0-9]+}}
+  if #_hasSymbol(Swift.Int.self) {}
+}
+
+// We should not generate a #_hasSymbol query helper for Swift.Int.
+// CHECK-NOT: sSiTwS