Sema: Fix crash with metatype construction -vs- dynamic Self

Fixes <rdar://problem/31297864>.

Author: slavapestov

lib/Sema/CSSimplify.cpp

@@ -2364,7 +2364,12 @@ ConstraintSystem::simplifyConstructionConstraint(
   NameLookupOptions lookupOptions = defaultConstructorLookupOptions;
   if (isa<AbstractFunctionDecl>(useDC))
     lookupOptions |= NameLookupFlags::KnownPrivate;
-  auto ctors = TC.lookupConstructors(useDC, valueType, lookupOptions);
+
+  auto instanceType = valueType;
+  if (auto *selfType = instanceType->getAs<DynamicSelfType>())
+    instanceType = selfType->getSelfType();
+
+  auto ctors = TC.lookupConstructors(useDC, instanceType, lookupOptions);
   if (!ctors)
     return SolutionKind::Error;
 

test/decl/func/dynamic_self.swift

@@ -91,6 +91,13 @@ class C1 {
 
     return Self() // expected-error{{use of unresolved identifier 'Self'}} expected-note {{did you mean 'self'?}}
   }
+
+  // This used to crash because metatype construction went down a
+  // different code path that didn't handle DynamicSelfType.
+  class func badFactory() -> Self {
+    return self(int: 0)
+    // expected-error@-1 {{initializing from a metatype value must reference 'init' explicitly}}
+  }
 }
 
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