RequirementMachine: Turn off redundant requirement warnings by default and add -warn-redundant-requirements frontend flag

Author: slavapestov

include/swift/Basic/LangOptions.h

@@ -569,6 +569,9 @@ namespace swift {
     /// rewrite system.
     bool EnableRequirementMachineOpaqueArchetypes = false;
 
+    /// Enable warnings for redundant requirements in generic signatures.
+    bool WarnRedundantRequirements = false;
+
     /// Enables dumping type witness systems from associated type inference.
     bool DumpTypeWitnessSystems = false;
 

include/swift/Option/FrontendOptions.td

@@ -378,6 +378,9 @@ def disable_requirement_machine_reuse : Flag<["-"], "disable-requirement-machine
 def enable_requirement_machine_opaque_archetypes : Flag<["-"], "enable-requirement-machine-opaque-archetypes">,
   HelpText<"Enable more correct opaque archetype support, which is off by default because it might fail to produce a convergent rewrite system">;
 
+def warn_redundant_requirements : Flag<["-"], "warn-redundant-requirements">,
+  HelpText<"Emit warnings for redundant requirements in generic signatures">;
+
 def dump_type_witness_systems : Flag<["-"], "dump-type-witness-systems">,
   HelpText<"Enables dumping type witness systems from associated type inference">;
 

lib/AST/RequirementMachine/Diagnostics.cpp

@@ -138,6 +138,11 @@ bool swift::rewriting::diagnoseRequirementErrors(
     }
 
     case RequirementError::Kind::RedundantRequirement: {
+      // We only emit redundant requirement warnings if the user passed
+      // the -warn-redundant-requirements frontend flag.
+      if (!ctx.LangOpts.WarnRedundantRequirements)
+        break;
+
       auto requirement = error.requirement;
       if (requirement.hasError())
         break;

lib/Frontend/CompilerInvocation.cpp

@@ -1046,6 +1046,9 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
   if (Args.hasArg(OPT_enable_requirement_machine_opaque_archetypes))
     Opts.EnableRequirementMachineOpaqueArchetypes = true;
 
+  if (Args.hasArg(OPT_warn_redundant_requirements))
+    Opts.WarnRedundantRequirements = true;
+
   Opts.DumpTypeWitnessSystems = Args.hasArg(OPT_dump_type_witness_systems);
 
   return HadError || UnsupportedOS || UnsupportedArch;

test/AutoDiff/SILGen/differentiability_witness_generic_signature.swift

@@ -1,5 +1,5 @@
-// RUN: %target-swift-emit-silgen -verify -module-name main %s -requirement-machine-inferred-signatures=on | %FileCheck %s
-// RUN: %target-swift-emit-sil -verify -module-name main %s -requirement-machine-inferred-signatures=on
+// RUN: %target-swift-emit-silgen -verify -module-name main %s -requirement-machine-inferred-signatures=on -warn-redundant-requirements | %FileCheck %s
+// RUN: %target-swift-emit-sil -verify -module-name main %s -requirement-machine-inferred-signatures=on -warn-redundant-requirements
 
 // NOTE(SR-11950): SILParser crashes for SILGen round-trip.
 

test/AutoDiff/SILOptimizer/generics.swift

@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-sil -verify %s -requirement-machine-inferred-signatures=on | %FileCheck %s -check-prefix=CHECK-SIL
+// RUN: %target-swift-emit-sil -verify %s -requirement-machine-inferred-signatures=on -warn-redundant-requirements | %FileCheck %s -check-prefix=CHECK-SIL
 
 import _Differentiation
 

test/Compatibility/anyobject_class.swift

@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift -swift-version 4 -requirement-machine-protocol-signatures=on
+// RUN: %target-typecheck-verify-swift -swift-version 4 -requirement-machine-protocol-signatures=on -warn-redundant-requirements
 // RUN: not %target-swift-frontend -typecheck -swift-version 5 -requirement-machine-protocol-signatures=on
 
 protocol P : class, AnyObject { } // expected-warning{{redundant inheritance from 'AnyObject' and Swift 3 'class' keyword}}{{14-21=}}

test/Constraints/generic_super_constraint.swift

@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift %s -requirement-machine-inferred-signatures=on
+// RUN: %target-typecheck-verify-swift %s -requirement-machine-inferred-signatures=on -warn-redundant-requirements
 
 class Base<T> { }
 class Derived: Base<Int> { }

test/Constraints/same_types.swift

@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift -requirement-machine-inferred-signatures=on
+// RUN: %target-typecheck-verify-swift -requirement-machine-inferred-signatures=on -warn-redundant-requirements
 // RUN: not %target-swift-frontend -typecheck %s -debug-generic-signatures -requirement-machine-inferred-signatures=on 2>&1 | %FileCheck %s
 
 protocol Fooable {

test/Generics/associated_type_typo.swift

@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift -requirement-machine-protocol-signatures=on -requirement-machine-inferred-signatures=on
+// RUN: %target-typecheck-verify-swift -requirement-machine-protocol-signatures=on -requirement-machine-inferred-signatures=on -warn-redundant-requirements
 
 // RUN: not %target-swift-frontend -typecheck -debug-generic-signatures %s -requirement-machine-protocol-signatures=on -requirement-machine-inferred-signatures=on > %t.dump 2>&1 
 // RUN: %FileCheck -check-prefix CHECK-GENERIC %s < %t.dump