[Diag] Reword the tuple shuffle diagnostic

"reorder" seems a bit less jargony than "shuffle", and include the 
labels that are being reordered.

include/swift/AST/DiagnosticsSema.def

@@ -7833,9 +7833,9 @@ ERROR(result_builder_buildpartialblock_accumulated_not_accessible,none,
 // MARK: Tuple Shuffle Diagnostics
 //------------------------------------------------------------------------------
 
- WARNING(warn_reordering_tuple_shuffle_deprecated,Deprecation,
-        "expression shuffles the elements of this tuple; "
-        "this behavior is deprecated", ())
+WARNING(warn_reordering_tuple_shuffle_deprecated,Deprecation,
+        "implicit reordering of tuple elements from '%0' to '%1' is deprecated",
+        (StringRef, StringRef))
 
 //------------------------------------------------------------------------------
 // MARK: Implicit conversion diagnostics

lib/Sema/CSApply.cpp

@@ -5818,6 +5818,7 @@ Expr *ExprRewriter::coerceTupleToTuple(Expr *expr,
 
   // Convert each OpaqueValueExpr to the correct type.
   SmallVector<Expr *, 4> converted;
+  SmallVector<Identifier, 4> origLabels;
   SmallVector<Identifier, 4> labels;
   SmallVector<TupleTypeElt, 4> convertedElts;
 
@@ -5825,6 +5826,7 @@ Expr *ExprRewriter::coerceTupleToTuple(Expr *expr,
   for (unsigned i = 0, e = sources.size(); i != e; ++i) {
     unsigned source = sources[i];
     auto *fromElt = destructured[source];
+    auto fromLabel = fromTuple->getElement(i).getName();
 
     // Actually convert the source element.
     auto toEltType = toTuple->getElementType(i);
@@ -5832,8 +5834,7 @@ Expr *ExprRewriter::coerceTupleToTuple(Expr *expr,
 
     // If we're shuffling positions and labels, we have to warn about this
     // conversion.
-    if (i != sources[i] &&
-        fromTuple->getElement(i).getName() != toLabel)
+    if (i != sources[i] && fromLabel != toLabel)
       anythingShuffled = true;
 
     auto *toElt
@@ -5845,6 +5846,7 @@ Expr *ExprRewriter::coerceTupleToTuple(Expr *expr,
 
     converted.push_back(toElt);
     labels.push_back(toLabel);
+    origLabels.push_back(fromLabel);
     convertedElts.emplace_back(toEltType, toLabel);
   }
 
@@ -5852,8 +5854,22 @@ Expr *ExprRewriter::coerceTupleToTuple(Expr *expr,
   // will form the shuffle for now, but a future compiler should decline to
   // do so and begin the process of removing them altogether.
   if (anythingShuffled) {
-    ctx.Diags.diagnose(
-        expr->getLoc(), diag::warn_reordering_tuple_shuffle_deprecated);
+    auto concatLabels = [](SmallVectorImpl<Identifier> &labels,
+                           SmallVectorImpl<char> &out) {
+      llvm::raw_svector_ostream OS(out);
+      for (auto label : labels) {
+        DeclName(label).print(OS, /*skipEmpty*/ false, /*escapeIfNeeded*/ true);
+        OS << ':';
+      }
+    };
+    SmallString<16> fromLabelStr;
+    concatLabels(origLabels, fromLabelStr);
+    SmallString<16> toLabelStr;
+    concatLabels(labels, toLabelStr);
+
+    ctx.Diags.diagnose(expr->getLoc(),
+                       diag::warn_reordering_tuple_shuffle_deprecated,
+                       fromLabelStr, toLabelStr);
   }
 
   // Create the result tuple, written in terms of the destructured

test/Constraints/tuple_shuffle.swift

@@ -5,27 +5,32 @@ func consume<T>(_ x: T) {} // Suppress unused variable warnings
 func shuffle_through_initialization() {
   let a = (x: 1, y: 2)
   let b: (y: Int, x: Int)
-  b = a // expected-warning {{expression shuffles the elements of this tuple}}
+  b = a // expected-warning {{implicit reordering of tuple elements from 'x:y:' to 'y:x:' is deprecated}}
   consume(b)
 }
 
+func shuffle_raw_label(_ t: (`a b`: Int, `c d`: Int)) {
+  let _: (`c d`: Int, `a b`: Int) = t
+  // expected-warning@-1 {{implicit reordering of tuple elements from '`a b`:`c d`:' to '`c d`:`a b`:' is deprecated}}
+}
+
 func shuffle_through_destructuring() {
   let a = (x: 1, y: 2)
-  let (y: b, x: c) = a // expected-warning {{expression shuffles the elements of this tuple}}
+  let (y: b, x: c) = a // expected-warning {{implicit reordering of tuple elements from 'x:y:' to 'y:x:' is deprecated}}
   consume((b, c))
 }
 
 func shuffle_through_call() {
   func foo(_ : (x: Int, y: Int)) {}
-  foo((y: 5, x: 10)) // expected-warning {{expression shuffles the elements of this tuple}}
+  foo((y: 5, x: 10)) // expected-warning {{implicit reordering of tuple elements from 'y:x:' to 'x:y:' is deprecated}}
 }
 
 func shuffle_through_cast() {
-  let x = ((a: Int(), b: Int()) as (b: Int, a: Int)).0 // expected-warning {{expression shuffles the elements of this tuple}}
+  let x = ((a: Int(), b: Int()) as (b: Int, a: Int)).0 // expected-warning {{implicit reordering of tuple elements from 'a:b:' to 'b:a:' is deprecated}}
 
   // Ah, the famous double-shuffle
   let (c1, (c2, c3)): (c: Int, (b: Int, a: Int)) = ((a: Int(), b: Int()), c: Int())
-  // expected-warning@-1 {{expression shuffles the elements of this tuple}}
-  // expected-warning@-2 {{expression shuffles the elements of this tuple}}
+  // expected-warning@-1 {{implicit reordering of tuple elements from 'a:b:' to 'b:a:' is deprecated}}
+  // expected-warning@-2 {{implicit reordering of tuple elements from '_:c:' to 'c:_:' is deprecated}}
   consume((x, c1, c2, c3))
 }

test/Parse/omit_return.swift

@@ -474,7 +474,7 @@ func ff_implicitInjectIntoOptionalExpr(_ int: Int) -> Int? {
 }
 
 func ff_implicitTupleShuffle(_ input: (one: Int, two: Int)) -> (two: Int, one: Int) {
-    input // expected-warning {{expression shuffles the elements of this tuple; this behavior is deprecated}}
+    input // expected-warning {{implicit reordering of tuple elements from 'one:two:' to 'two:one:' is deprecated}}
 }
 
 func ff_implicitCollectionUpcast(_ derived: [Derived]) -> [Base] {

test/Parse/omit_return_ifdecl.swift

@@ -676,7 +676,7 @@ func ff_implicitInjectIntoOptionalExpr(_ int: Int) -> Int? {
 
 func ff_implicitTupleShuffle(_ input: (one: Int, two: Int)) -> (two: Int, one: Int) {
     #if true
-    input // expected-warning {{expression shuffles the elements of this tuple; this behavior is deprecated}}
+    input // expected-warning {{implicit reordering of tuple elements from 'one:two:' to 'two:one:' is deprecated}}
     #endif
 }
 

test/Sema/diag_unowned_immediate_deallocation.swift

@@ -452,10 +452,10 @@ func testGenericWeakClassDiag() {
 // The diagnostic doesn't currently support tuple shuffles.
 func testDontDiagnoseThroughTupleShuffles() {
   unowned let (c1, (c2, c3)): (c: C, (b: C, a: C)) = ((a: D(), b: C()), c: D())
-  // expected-warning@-1 {{expression shuffles the elements of this tuple; this behavior is deprecated}}
-  // expected-warning@-2 {{expression shuffles the elements of this tuple; this behavior is deprecated}}
+  // expected-warning@-1 {{implicit reordering of tuple elements from 'a:b:' to 'b:a:' is deprecated}}
+  // expected-warning@-2 {{implicit reordering of tuple elements from '_:c:' to 'c:_:' is deprecated}}
   unowned let c4 = ((a: C(), b: C()) as (b: C, a: C)).0
-  // expected-warning@-1 {{expression shuffles the elements of this tuple; this behavior is deprecated}}
+  // expected-warning@-1 {{implicit reordering of tuple elements from 'a:b:' to 'b:a:' is deprecated}}
 
   _ = c1; _ = c2; _ = c3; _ = c4
 }

test/decl/func/operator.swift

@@ -155,7 +155,7 @@ var f2 : (Int) -> Int = (+-+)
 var f3 : (inout Int) -> Int = (-+-) // expected-error{{ambiguous use of operator '-+-'}}
 var f4 : (inout Int, Int) -> Int = (+-+=)
 var r5 : (a : (Int, Int) -> Int, b : (Int, Int) -> Int) = (+, -)
-var r6 : (a : (Int, Int) -> Int, b : (Int, Int) -> Int) = (b : +, a : -) // expected-warning {{expression shuffles the elements of this tuple; this behavior is deprecated}}
+var r6 : (a : (Int, Int) -> Int, b : (Int, Int) -> Int) = (b : +, a : -) // expected-warning {{implicit reordering of tuple elements from 'b:a:' to 'a:b:' is deprecated}}
 
 struct f6_S {
   subscript(op : (Int, Int) -> Int) -> Int {

test/expr/closure/closures.swift

@@ -56,7 +56,7 @@ func funcdecl5(_ a: Int, _ y: Int) {
   var b = a.1+a.f
 
   // Tuple expressions with named elements.
-  var i : (y : Int, x : Int) = (x : 42, y : 11) // expected-warning {{expression shuffles the elements of this tuple; this behavior is deprecated}}
+  var i : (y : Int, x : Int) = (x : 42, y : 11) // expected-warning {{implicit reordering of tuple elements from 'x:y:' to 'y:x:' is deprecated}}
   funcdecl1(123, 444)
   
   // Calls.

test/expr/expressions.swift

@@ -194,7 +194,7 @@ func test5() {
 
 
   let c: (a: Int, b: Int) = (1,2)
-  let _: (b: Int, a: Int) = c  // expected-warning {{expression shuffles the elements of this tuple; this behavior is deprecated}}
+  let _: (b: Int, a: Int) = c  // expected-warning {{implicit reordering of tuple elements from 'a:b:' to 'b:a:' is deprecated}}
 }