GSB: We only care about 'derived from concrete' requirements when building requirement signatures

Once we can rebuild requirement signatures after dropping redundant
requirements, we won't need this at all.

Author: slavapestov

lib/AST/GenericSignatureBuilder.cpp

@@ -1096,12 +1096,14 @@ const RequirementSource *RequirementSource::getMinimalConformanceSource(
                                           ArchetypeResolutionKind::WellFormed);
       assert(parentEquivClass && "Not a well-formed type?");
 
-      if (parentEquivClass->concreteType)
-        derivedViaConcrete = true;
-      else if (parentEquivClass->superclass &&
-               builder.lookupConformance(parentEquivClass->superclass,
-                                         source->getProtocolDecl()))
-        derivedViaConcrete = true;
+      if (requirementSignatureSelfProto) {
+        if (parentEquivClass->concreteType)
+          derivedViaConcrete = true;
+        else if (parentEquivClass->superclass &&
+                 builder.lookupConformance(parentEquivClass->superclass,
+                                           source->getProtocolDecl()))
+          derivedViaConcrete = true;
+      }
 
       // The parent potential archetype must conform to the protocol in which
       // this requirement resides. Add this constraint.
@@ -7200,6 +7202,9 @@ void GenericSignatureBuilder::diagnoseRedundantRequirements() const {
 
       for (auto otherReq : found->second) {
         auto *otherSource = otherReq.getSource();
+        if (otherSource->isInferredRequirement())
+          continue;
+
         auto otherLoc = otherSource->getLoc();
         if (otherLoc.isInvalid())
           continue;
@@ -7237,6 +7242,9 @@ void GenericSignatureBuilder::diagnoseRedundantRequirements() const {
 
         for (auto otherReq : found->second) {
           auto *otherSource = otherReq.getSource();
+          if (otherSource->isInferredRequirement())
+            continue;
+
           auto otherLoc = otherSource->getLoc();
           if (otherLoc.isInvalid())
             continue;
@@ -7276,6 +7284,9 @@ void GenericSignatureBuilder::diagnoseRedundantRequirements() const {
 
         for (auto otherReq : found->second) {
           auto *otherSource = otherReq.getSource();
+          if (otherSource->isInferredRequirement())
+            continue;
+
           auto otherLoc = otherSource->getLoc();
           if (otherLoc.isInvalid())
             continue;

test/Generics/rdar75656022.swift

@@ -49,7 +49,8 @@ struct OriginalExampleWithWarning<A, B> where A : P2, B : P2, A.T == B.T {
     where C : P1,
           D : P1, // expected-warning {{redundant conformance constraint 'D' : 'P1'}}
           C.T : P1, // expected-warning {{redundant conformance constraint 'C.T' : 'P1'}}
-          A == S1<C, C.T.T, S2<C.T>>,
+          A == S1<C, C.T.T, S2<C.T>>, // expected-note {{conformance constraint 'D' : 'P1' implied here}}
+          // expected-note@-1 {{conformance constraint 'C.T' : 'P1' implied here}}
           C.T == D,
           E == D.T { }
 }
@@ -71,6 +72,7 @@ struct WithoutBogusGenericParametersWithWarning<A, B> where A : P2, B : P2, A.T
     where C : P1,
           C.T : P1, // expected-warning {{redundant conformance constraint 'C.T' : 'P1'}}
           A == S1<C, C.T.T, S2<C.T>> {}
+          // expected-note@-1 {{conformance constraint 'C.T' : 'P1' implied here}}
 }
 
 // Same as above but without unnecessary generic parameters