Recheck UnresolvedSpecializeExpr after type variables are gone.

Author: Greg Titus

lib/Sema/CSApply.cpp

@@ -3225,8 +3225,18 @@ namespace {
     }
 
     Expr *visitUnresolvedSpecializeExpr(UnresolvedSpecializeExpr *expr) {
-      // Our specializations should have resolved the subexpr to the right type.
-      return expr->getSubExpr();
+      // Our specializations should have resolved the subexpr to the right type,
+      // recheck for validity.
+      auto subExpr = expr->getSubExpr();
+      auto ty = subExpr->getType();
+      if (ty && !ty->is<AnyMetatypeType>()) {
+        auto &de = cs.getASTContext().Diags;
+        de.diagnose(subExpr->getLoc(), diag::not_a_generic_definition);
+        de.diagnose(expr->getLAngleLoc(),
+                    diag::while_parsing_as_left_angle_bracket);
+        return nullptr;
+      }
+      return subExpr;
     }
 
     Expr *visitMemberRefExpr(MemberRefExpr *expr) {

test/Sema/generic-arg-list.swift

@@ -0,0 +1,26 @@
+// RUN: %target-typecheck-verify-swift
+
+extension Int {
+  func foo() -> Int {}
+  var bar: Int {
+    get {}
+  }
+
+  func baz() -> Int {}
+  func baz(_ x: Int = 0) -> Int {}
+}
+
+func test(i: Int) {
+  // Error
+  let _ = i.foo<Int>() // expected-error {{cannot explicitly specialize a generic function}}
+    // expected-note@-1 {{while parsing this '<' as a type parameter bracket}}
+  let _ = i.bar<Int> // expected-error {{'>' is not a postfix unary operator}}
+
+  // Now also Error
+  let _ = 0.foo<Int>() // expected-error {{cannot specialize a non-generic definition}}
+    // expected-note@-1 {{while parsing this '<' as a type parameter bracket}}
+  let _ = 0.bar<Int> // expected-error {{'>' is not a postfix unary operator}}
+
+  let _ = i.baz<Int> // expected-error {{cannot specialize a non-generic definition}}
+    // expected-note@-1 {{while parsing this '<' as a type parameter bracket}}
+}