RequirementMachine: Concrete contraction discards errors from inferred requirements

Author: slavapestov

lib/AST/RequirementMachine/ConcreteContraction.cpp

@@ -598,7 +598,13 @@ bool ConcreteContraction::performConcreteContraction(
     // Otherwise, desugar the requirement again, since we might now have a
     // requirement where the left hand side is not a type parameter.
     SmallVector<Requirement, 4> reqs;
-    desugarRequirement(substReq, req.loc, reqs, errors);
+    if (req.inferred) {
+      SmallVector<RequirementError, 4> discardErrors;
+      desugarRequirement(substReq, SourceLoc(), reqs, discardErrors);
+    } else {
+      desugarRequirement(substReq, req.loc, reqs, errors);
+    }
+
     for (auto desugaredReq : reqs) {
       if (Debug) {
         llvm::dbgs() << "@@ Desugared requirement: ";

test/Compatibility/stdlib_generic_typealiases.swift

@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift
+// RUN: %target-typecheck-verify-swift -requirement-machine-inferred-signatures=on
 
 struct RequiresStrideable<T: Strideable> { }
 

test/Constraints/casts.swift

@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift -enable-objc-interop
+// RUN: %target-typecheck-verify-swift -enable-objc-interop -requirement-machine-inferred-signatures=on
 
 class B { 
   init() {} 

test/Generics/indirectly_concrete_generic_param.swift

@@ -1,5 +1,5 @@
-// RUN: %target-typecheck-verify-swift
-// RUN: %target-swift-frontend -typecheck %s -debug-generic-signatures 2>&1 | %FileCheck %s
+// RUN: %target-typecheck-verify-swift -requirement-machine-inferred-signatures=on
+// RUN: %target-swift-frontend -typecheck %s -debug-generic-signatures -requirement-machine-inferred-signatures=on 2>&1 | %FileCheck %s
 
 class S<T, U> where T : P, U == T.T {}
 

test/decl/circularity.swift

@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift
+// RUN: %target-typecheck-verify-swift -requirement-machine-inferred-signatures=on
 
 // N.B. Validating the pattern binding initializer for `pickMe` used to cause
 // recursive validation of the VarDecl. Check that we don't regress now that