Diagnose the first and third operands of a C-style for loop

as ignored expressions. Swift SVN r32291
miichy · Sep 29, 2015 · 7eb830f · 7eb830f
1 parent e27b1e7
commit 7eb830f
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Showing 3 changed files with 27 additions and 12 deletions.
diff --git a/lib/Sema/TypeCheckStmt.cpp b/lib/Sema/TypeCheckStmt.cpp
@@ -519,6 +519,7 @@ class StmtChecker : public StmtVisitor<StmtChecker, Stmt*> {
                                  TypeCheckExprFlags::IsDiscarded))
         return nullptr;
       FS->setInitializer(Initializer);
+      TC.checkIgnoredExpr(Initializer);
     }
 
     if (auto *Cond = FS->getCond().getPtrOrNull()) {
@@ -532,6 +533,7 @@ class StmtChecker : public StmtVisitor<StmtChecker, Stmt*> {
                                  TypeCheckExprFlags::IsDiscarded))
         return nullptr;
       FS->setIncrement(Increment);
+      TC.checkIgnoredExpr(Increment);
     }
 
     AddLabeledStmt loopNest(*this, FS);
@@ -964,6 +966,16 @@ bool TypeChecker::typeCheckCatchPattern(CatchStmt *S, DeclContext *DC) {
 }
 
 void TypeChecker::checkIgnoredExpr(Expr *E) {
+  // For parity with C, several places in the grammar accept multiple
+  // comma-separated expressions and then bind them together as an implicit
+  // tuple.  Break these apart and check them separately.
+  if (E->isImplicit() && isa<TupleExpr>(E)) {
+    for (auto Elt : cast<TupleExpr>(E)->getElements()) {
+      checkIgnoredExpr(Elt);
+    }
+    return;
+  }
+
   // Complain about l-values that are neither loaded nor stored.
   if (E->getType()->isLValueType()) {
     diagnose(E->getLoc(), diag::expression_unused_lvalue)

diff --git a/test/SILGen/statements.swift b/test/SILGen/statements.swift
@@ -233,13 +233,6 @@ func for_each_loop(x: [C]) {
   _ = 0
 }
 
-// <rdar://problem/16650625>
-func for_ignored_lvalue_init() {
-  var i = 0
-  for i; i < 10; ++i {}
-}
-
-
 // CHECK-LABEL: sil hidden @{{.*}}test_break
 func test_break(i : Int) {
   switch i {
@@ -353,11 +346,6 @@ func test_if_break(a : Bool) {
   // CHECK:   return
 }
 
-// rdar://problem/18643692
-func for_loop_multi_iter() {
-  for (var i = 0, x = 0; i < 10; i++, x) { --x }
-}
-
 // CHECK-LABEL: sil hidden @_TF10statements7test_doFT_T_
 func test_do() {
   // CHECK: [[BAR:%.*]] = function_ref @_TF10statements3barFSiT_

diff --git a/test/stmt/statements.swift b/test/stmt/statements.swift
@@ -423,4 +423,19 @@ func testThrowNil() throws {
 }
 
 
+// <rdar://problem/16650625>
+func for_ignored_lvalue_init() {
+  var i = 0
+  for i;  // expected-error {{expression resolves to an unused l-value}}
+    i < 10; ++i {}
+}
+
+// rdar://problem/18643692
+func for_loop_multi_iter() {
+  for (var i = 0, x = 0; i < 10; i++,
+       x) { // expected-error {{expression resolves to an unused l-value}}
+    --x
+  }
+}
+