[Constraint solver] Use the type representative in the "occurs" check.

lib/Sema/CSSimplify.cpp

@@ -1288,6 +1288,7 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
       bool wantRvalue = kind == ConstraintKind::Equal;
       if (typeVar1) {
         // Simplify the right-hand type and perform the "occurs" check.
+        typeVar1 = getRepresentative(typeVar1);
         type2 = simplifyType(type2);
         if (typeVarOccursInType(typeVar1, type2))
           return formUnsolvedResult();
@@ -1332,10 +1333,11 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
         return SolutionKind::Solved;
       }
 
-        // Simplify the left-hand type and perform the "occurs" check.
-        type1 = simplifyType(type1);
-        if (typeVarOccursInType(typeVar2, type1))
-          return formUnsolvedResult();
+      // Simplify the left-hand type and perform the "occurs" check.
+      typeVar2 = getRepresentative(typeVar2);
+      type1 = simplifyType(type1);
+      if (typeVarOccursInType(typeVar2, type1))
+        return formUnsolvedResult();
 
       // If we want an rvalue, get the rvalue.
       if (wantRvalue)
@@ -1355,6 +1357,7 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
     case ConstraintKind::BindParam: {
       if (typeVar2 && !typeVar1) {
         // Simplify the left-hand type and perform the "occurs" check.
+        typeVar2 = getRepresentative(typeVar2);
         type1 = simplifyType(type1);
         if (typeVarOccursInType(typeVar2, type1))
           return formUnsolvedResult();
@@ -1367,6 +1370,7 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
         return SolutionKind::Solved;
       } else if (typeVar1 && !typeVar2) {
         // Simplify the right-hand type and perform the "occurs" check.
+        typeVar1 = getRepresentative(typeVar1);
         type2 = simplifyType(type2);
         if (typeVarOccursInType(typeVar1, type2))
           return formUnsolvedResult();

lib/Sema/ConstraintSystem.cpp

@@ -103,14 +103,6 @@ bool ConstraintSystem::typeVarOccursInType(TypeVariableType *typeVar,
 void ConstraintSystem::assignFixedType(TypeVariableType *typeVar, Type type,
                                        bool updateState) {
 
-  // If the type to be fixed is an optional type that wraps the type parameter
-  // itself, we do not want to go through with the assignment. To do so would
-  // force the type variable to be adjacent to itself.
-  if (auto optValueType = type->getOptionalObjectType()) {
-    if (optValueType->isEqual(typeVar))
-      return;
-  }
-
   typeVar->getImpl().assignFixedType(type, getSavedBindings());
 
   if (!updateState)

test/Constraints/generics.swift

@@ -402,3 +402,8 @@ func testFixItNested() {
     FullyGeneric<Any>()
   )
 }
+
+// rdar://problem/26845038
+func occursCheck26845038(a: [Int]) {
+  _ = Array(a)[0]
+}

test/Constraints/optional.swift

@@ -141,3 +141,9 @@ protocol PPPP {
 func compare<T: PPPP>(v: T, u: T!) -> Bool {
   return v ++++ u
 }
+
+func sr2752(x: String?, y: String?) {
+  _ = x.map { xx in
+    y.map { _ in "" } ?? "\(xx)"
+  }
+}

validation-test/Sema/type_checker_crashers_fixed/rdar27148148.swift

@@ -1,5 +1,4 @@
 // RUN: not %target-swift-frontend %s -parse
-// REQUIRES: asserts
 
 public protocol I {
   associatedtype X : Equatable

validation-test/Sema/type_checker_crashers_fixed/sr1512.swift

@@ -0,0 +1,57 @@
+// RUN: not %target-swift-frontend %s -parse
+
+public struct CollectionWrapper<C:RangeReplaceableCollection where C.Index:Comparable> {
+
+	public private(set) var collection : C
+
+	private init(wrappingCollection: C) {
+		collection = wrappingCollection
+	}
+}
+
+// Export Collection API
+
+extension CollectionWrapper : Collection {
+
+	public var startIndex: C.Index { return collection.startIndex }
+	public var endIndex  : C.Index { return collection.endIndex   }
+
+	public func makeIterator() -> C.Iterator {
+		return collection.makeIterator()
+	}
+
+	public subscript (position: C.Index) -> C.Iterator.Element { return collection[position] }
+
+	public subscript (bounds: Range<C.Index>) -> C.SubSequence { return collection[bounds] }
+
+	public func prefix(upTo end: C.Index) -> C.SubSequence { return collection.prefix(upTo: end) }
+
+	public func suffix(from start: C.Index) -> C.SubSequence { return collection.suffix(from: start) }
+
+	public func prefix(through position: C.Index) -> C.SubSequence { return collection.prefix(through: position) }
+
+	public var isEmpty: Bool { return collection.isEmpty }
+
+    public var count: C.IndexDistance { return collection.count }
+
+    public var first: C.Iterator.Element? { return collection.first }
+
+	public func index(after idx: C.Index) -> C.Index { return collection.index(after: idx) }
+
+	public func index(_ idx: C.Index, offsetBy offset: C.IndexDistance, limitedBy limit: C.Index? = nil) -> C.Index {
+		return collection.index(idx, offsetBy: offset, limitedBy: limit)
+	}
+}
+
+// Export RangeReplaceableCollection API
+
+extension CollectionWrapper : RangeReplaceableCollection {
+
+	public init() {
+		self.init(wrappingCollection: C())
+	}
+
+	public mutating func replaceSubrange<D : Collection where D.Iterator.Element == C.Iterator.Element>(_ subRange: Range<C.Index>, with newElements: D) {
+		collection.replaceSubrange(subRange, with: newElements)
+	}
+}

validation-test/Sema/type_checker_crashers_fixed/sr1902.swift

@@ -0,0 +1,22 @@
+// RUN: not %target-swift-frontend %s -parse
+struct A {
+    var a: Int32 { return 0 }
+}
+
+struct B {
+    var b: Int64 { return 0 }
+}
+
+struct C {
+    var c: Int64 { return 0 }
+}
+
+class S {
+    var a: A? = A()
+    var b: B? = B()
+    var c: C? = C()
+    var result: Int64? { return a?.a ?? b?.b ?? c?.c }
+}
+
+let s = S()
+print(s.result)

validation-test/Sema/type_checker_crashers_fixed/sr2635.swift

@@ -0,0 +1,62 @@
+// RUN: %target-swift-frontend %s -parse
+
+//
+//  main.swift
+//  TypeBasics
+//
+//  Created by David Scrève on 16/11/2014.
+//  Copyright (c) 2014 David Scrève. All rights reserved.
+//
+
+let constante : String = "Hello World"
+
+
+let constante2 = "Hello World"
+
+let caractere : Character = Array(constante.characters)[0]
+
+let caractere2 : Character = "A"
+
+var variable : String
+
+
+var chaine = "Bonjour le monde"
+
+
+var nombre  : Int = 3
+
+nombre=5
+
+var valeur : Int32
+
+valeur = Int32(nombre)
+
+
+
+print("la valeur vaut : \(valeur)")
+
+
+if (valeur > 3)
+{
+    print(">3")
+}
+else
+{
+    print("<=3")
+}
+
+switch(valeur)
+{
+case 0:
+    print("0");
+
+case 1,2:
+    print("1");
+
+case 10...100:
+    print("Interval");
+
+default:
+    print("default");
+}
+