[ConstraintSystem] Make it possible to anchor a target on a pattern

Author: xedin

include/swift/Sema/ConstraintSystem.h

@@ -966,6 +966,7 @@ class SolutionApplicationTargetsKey {
     stmtCondElement,
     expr,
     stmt,
+    pattern,
     patternBindingEntry,
     varDecl,
   };
@@ -980,6 +981,8 @@ class SolutionApplicationTargetsKey {
 
     const Stmt *stmt;
 
+    const Pattern *pattern;
+
     struct PatternBindingEntry {
       const PatternBindingDecl *patternBinding;
       unsigned index;
@@ -1009,6 +1012,11 @@ class SolutionApplicationTargetsKey {
     storage.stmt = stmt;
   }
 
+  SolutionApplicationTargetsKey(const Pattern *pattern) {
+    kind = Kind::pattern;
+    storage.pattern = pattern;
+  }
+
   SolutionApplicationTargetsKey(
       const PatternBindingDecl *patternBinding, unsigned index) {
     kind = Kind::patternBindingEntry;
@@ -1040,6 +1048,9 @@ class SolutionApplicationTargetsKey {
     case Kind::stmt:
       return lhs.storage.stmt == rhs.storage.stmt;
 
+    case Kind::pattern:
+      return lhs.storage.pattern == rhs.storage.pattern;
+
     case Kind::patternBindingEntry:
       return (lhs.storage.patternBindingEntry.patternBinding
                 == rhs.storage.patternBindingEntry.patternBinding) &&
@@ -1081,6 +1092,11 @@ class SolutionApplicationTargetsKey {
           DenseMapInfo<unsigned>::getHashValue(static_cast<unsigned>(kind)),
           DenseMapInfo<void *>::getHashValue(storage.stmt));
 
+    case Kind::pattern:
+      return hash_combine(
+          DenseMapInfo<unsigned>::getHashValue(static_cast<unsigned>(kind)),
+          DenseMapInfo<void *>::getHashValue(storage.pattern));
+
     case Kind::patternBindingEntry:
       return hash_combine(
           DenseMapInfo<unsigned>::getHashValue(static_cast<unsigned>(kind)),