[CS] Visit all fixed bindings for constraint re-activation

This fixes a correctness issue with the old
implementation where we could fail to re-activate
a coercion constraint, and then let invalid code
get past Sema, causing either miscompiles or
crashes later down the pipeline.

Author: hamishknight

lib/Sema/ConstraintGraph.cpp

@@ -566,33 +566,39 @@ llvm::TinyPtrVector<Constraint *> ConstraintGraph::gatherConstraints(
         acceptConstraintFn(constraint);
   };
 
-  // Add constraints for the given adjacent type variable.
   llvm::SmallPtrSet<TypeVariableType *, 4> typeVars;
+  llvm::SmallPtrSet<Constraint *, 8> visitedConstraints;
+
+  if (kind == GatheringKind::AllMentions) {
+    // If we've been asked for "all mentions" of a type variable, search for
+    // constraints involving both it and its fixed bindings.
+    depthFirstSearch(
+        *this, typeVar,
+        [&](TypeVariableType *typeVar) {
+          return typeVars.insert(typeVar).second;
+        },
+        [&](Constraint *constraint) {
+          if (acceptConstraint(constraint))
+            constraints.push_back(constraint);
+
+          // Don't recurse into the constraint's type variables.
+          return false;
+        },
+        visitedConstraints);
+    return constraints;
+  }
+
+  // Add constraints for the given adjacent type variable.
 
   // Local function to add constraints
-  llvm::SmallPtrSet<Constraint *, 4> visitedConstraints;
   auto addConstraintsOfAdjacency = [&](TypeVariableType *adjTypeVar) {
-    ArrayRef<TypeVariableType *> adjTypeVarsToVisit;
-    switch (kind) {
-    case GatheringKind::EquivalenceClass:
-      adjTypeVarsToVisit = adjTypeVar;
-      break;
+    if (!typeVars.insert(adjTypeVar).second)
+      return;
 
-    case GatheringKind::AllMentions:
-      adjTypeVarsToVisit
-        = (*this)[CS.getRepresentative(adjTypeVar)].getEquivalenceClass();
-      break;
-    }
-
-    for (auto adjTypeVarEquiv : adjTypeVarsToVisit) {
-      if (!typeVars.insert(adjTypeVarEquiv).second)
-        continue;
-
-      for (auto constraint : (*this)[adjTypeVarEquiv].getConstraints()) {
-        if (visitedConstraints.insert(constraint).second &&
-            acceptConstraint(constraint))
-          constraints.push_back(constraint);
-      }
+    for (auto constraint : (*this)[adjTypeVar].getConstraints()) {
+      if (visitedConstraints.insert(constraint).second &&
+          acceptConstraint(constraint))
+        constraints.push_back(constraint);
     }
   };
 
@@ -613,20 +619,6 @@ llvm::TinyPtrVector<Constraint *> ConstraintGraph::gatherConstraints(
     for (auto adjTypeVar : node.getFixedBindings()) {
       addConstraintsOfAdjacency(adjTypeVar);
     }
-
-    switch (kind) {
-    case GatheringKind::EquivalenceClass:
-      break;
-
-    case GatheringKind::AllMentions:
-      // Retrieve the constraints from adjacent bindings.
-      for (auto adjTypeVar : node.getAdjacencies()) {
-        addConstraintsOfAdjacency(adjTypeVar);
-      }
-
-      break;
-    }
-
   }
 
   return constraints;

test/Constraints/bridging.swift

@@ -373,7 +373,7 @@ func bridgeTupleToAnyObject() {
 
 // Array defaulting and bridging type checking error per rdar://problem/54274245
 func rdar54274245(_ arr: [Any]?) {
-  _ = (arr ?? []) as [NSObject]
+  _ = (arr ?? []) as [NSObject] // expected-error {{type of expression is ambiguous without more context}}
 }
 
 // rdar://problem/60501780 - failed to infer NSString as a value type of a dictionary

test/Constraints/casts.swift

@@ -238,3 +238,28 @@ func test_tuple_casts_no_warn() {
   _ = arr as! [(a: Foo, Foo)] // expected-warning {{cast from '[(Any, Any)]' to unrelated type '[(a: Foo, Foo)]' always fails}}
   _ = tup as! (a: Foo, Foo) // expected-warning {{cast from '(Any, Any)' to unrelated type '(a: Foo, Foo)' always fails}}
 }
+
+infix operator ^^^
+func ^^^ <T> (lhs: T?, rhs: @autoclosure () -> T) -> T { lhs! }
+func ^^^ <T> (lhs: T?, rhs: @autoclosure () -> T?) -> T? { lhs! }
+
+// SR-12369: Make sure we don't drop the coercion constraint.
+func test_coercions_with_overloaded_operator(str: String, optStr: String?, veryOptString: String????) {
+  _ = (str ?? "") as Int // expected-error {{cannot convert value of type 'String' to type 'Int' in coercion}}
+  _ = (optStr ?? "") as Int // expected-error {{cannot convert value of type 'String' to type 'Int' in coercion}}
+  _ = (optStr ?? "") as Int? // expected-error {{cannot convert value of type 'String' to type 'Int?' in coercion}}
+
+  _ = (str ^^^ "") as Int // expected-error {{cannot convert value of type 'String' to type 'Int' in coercion}}
+  _ = (optStr ^^^ "") as Int // expected-error {{cannot convert value of type 'String' to type 'Int' in coercion}}
+  _ = (optStr ^^^ "") as Int? // expected-error {{cannot convert value of type 'String' to type 'Int?' in coercion}}
+
+  _ = ([] ?? []) as String // expected-error {{cannot convert value of type '[Any]' to type 'String' in coercion}}
+  _ = ([""] ?? []) as [Int: Int] // expected-error {{cannot convert value of type '[String]' to type '[Int : Int]' in coercion}}
+  _ = (["": ""] ?? [:]) as [Int] // expected-error {{cannot convert value of type '[String : String]' to type '[Int]' in coercion}}
+  _ = (["": ""] ?? [:]) as Set<Int> // expected-error {{cannot convert value of type '[String : String]' to type 'Set<Int>' in coercion}}
+  _ = (["": ""] ?? [:]) as Int? // expected-error {{cannot convert value of type '[String : String]' to type 'Int?' in coercion}}
+
+  _ = ("" ?? "" ?? "") as Float // expected-error {{cannot convert value of type 'String' to type 'Float' in coercion}}
+  _ = (veryOptString ?? "" ?? "") as [String] // expected-error {{cannot convert value of type 'String???' to type '[String]' in coercion}}
+  _ = (veryOptString ?? "" ?? "" ?? "" ?? "") as [String] // expected-error {{cannot convert value of type 'String???' to type '[String]' in coercion}}
+}

validation-test/Sema/type_checker_perf/slow/sr139.swift renamed to validation-test/Sema/type_checker_perf/fast/sr139.swift

@@ -3,6 +3,5 @@
 
 // SR-139:
 // Infinite recursion parsing bitwise operators
-// expected-error@+1 {{unable to type-check this expression in reasonable time}}
 let x = UInt32(0x1FF)&0xFF << 24 | UInt32(0x1FF)&0xFF << 16 | UInt32(0x1FF)&0xFF << 8 | (UInt32(0x1FF)&0xFF)