[TypeChecker] SE-0347: Enable type inference from default expressions

(cherry picked from commit b03021d)

Author: xedin

include/swift/Basic/LangOptions.h

@@ -752,10 +752,6 @@ namespace swift {
     /// closures.
     bool EnableMultiStatementClosureInference = true;
 
-    /// Enable experimental support for generic parameter inference in
-    /// parameter positions from associated default expressions.
-    bool EnableTypeInferenceFromDefaultArguments = false;
-
     /// See \ref FrontendOptions.PrintFullConvention
     bool PrintFullConvention = false;
   };

lib/Frontend/CompilerInvocation.cpp

@@ -1107,9 +1107,6 @@ static bool ParseTypeCheckerArgs(TypeCheckerOptions &Opts, ArgList &Args,
   Opts.EnableMultiStatementClosureInference |=
       Args.hasArg(OPT_experimental_multi_statement_closures);
 
-  Opts.EnableTypeInferenceFromDefaultArguments |=
-      Args.hasArg(OPT_experimental_type_inference_from_defaults);
-
   Opts.PrintFullConvention |=
       Args.hasArg(OPT_experimental_print_full_convention);
 

lib/Sema/CSSimplify.cpp

@@ -1780,7 +1780,8 @@ static ConstraintSystem::TypeMatchResult matchCallArguments(
     if (parameterBindings[paramIdx].empty() && callee) {
       auto &ctx = cs.getASTContext();
 
-      if (ctx.TypeCheckerOpts.EnableTypeInferenceFromDefaultArguments) {
+      // Type inference from default value expressions.
+      {
         auto *paramList = getParameterList(callee);
         if (!paramList)
           continue;

lib/Sema/TypeCheckConstraints.cpp

@@ -464,10 +464,6 @@ Type TypeChecker::typeCheckParameterDefault(Expr *&defaultValue,
       return defaultValue->getType();
     }
 
-    // If inference is disabled, fail.
-    if (!ctx.TypeCheckerOpts.EnableTypeInferenceFromDefaultArguments)
-      return Type();
-
     // Caller-side defaults are always type-checked based on the concrete
     // type of the argument deduced at a particular call site.
     if (isa<MagicIdentifierLiteralExpr>(defaultValue))

test/Constraints/type_inference_from_default_exprs.swift

@@ -1,6 +1,6 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swift-frontend-emit-module -emit-module-path %t/InferViaDefaults.swiftmodule -enable-experimental-type-inference-from-defaults -module-name InferViaDefaults %S/Inputs/type_inference_via_defaults_other_module.swift
-// RUN: %target-swift-frontend -enable-experimental-type-inference-from-defaults -module-name main -typecheck -verify -I %t %s %S/Inputs/type_inference_via_defaults_other_module.swift
+// RUN: %target-swift-frontend-emit-module -emit-module-path %t/InferViaDefaults.swiftmodule -module-name InferViaDefaults %S/Inputs/type_inference_via_defaults_other_module.swift
+// RUN: %target-swift-frontend -module-name main -typecheck -verify -I %t %s %S/Inputs/type_inference_via_defaults_other_module.swift
 
 func testInferFromResult<T>(_: T = 42) -> T { fatalError() } // Ok
 

test/Constraints/type_inference_from_default_exprs_executable_test.swift

@@ -1,6 +1,6 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swift-frontend-emit-module -emit-module-path %t/InferViaDefaults.swiftmodule -enable-experimental-type-inference-from-defaults -module-name InferViaDefaults %S/Inputs/type_inference_via_defaults_other_module.swift
-// RUN: %target-build-swift -module-name main -Xfrontend -enable-experimental-type-inference-from-defaults -parse-as-library -I %t %s %S/Inputs/type_inference_via_defaults_other_module.swift -o %t/a.out
+// RUN: %target-swift-frontend-emit-module -emit-module-path %t/InferViaDefaults.swiftmodule -module-name InferViaDefaults %S/Inputs/type_inference_via_defaults_other_module.swift
+// RUN: %target-build-swift -module-name main -Xfrontend -parse-as-library -I %t %s %S/Inputs/type_inference_via_defaults_other_module.swift -o %t/a.out
 // RUN: %target-run %t/a.out | %FileCheck %s --color
 
 // REQUIRES: OS=macosx && CPU=x86_64

test/decl/func/vararg.swift

@@ -1,5 +1,4 @@
 // RUN: %target-typecheck-verify-swift
-// RUN: %target-typecheck-verify-swift -enable-experimental-type-inference-from-defaults
 
 var t1a: (Int...) = (1)
 // expected-error@-1 {{cannot create a variadic tuple}}

test/expr/closure/basic.swift

@@ -1,5 +1,4 @@
 // RUN: %target-typecheck-verify-swift
-// RUN: %target-typecheck-verify-swift -enable-experimental-type-inference-from-defaults
 
 func takeIntToInt(_ f: (Int) -> Int) { }
 func takeIntIntToInt(_ f: (Int, Int) -> Int) { }