GSB: Avoid re-resolving FloatingRequirementSources

Author: slavapestov

include/swift/AST/GenericSignatureBuilder.h

@@ -211,7 +211,7 @@ class GenericSignatureBuilder {
     bool recordConformanceConstraint(GenericSignatureBuilder &builder,
                                      ResolvedType type,
                                      ProtocolDecl *proto,
-                                     FloatingRequirementSource source);
+                                     const RequirementSource *source);
 
     /// Find a source of the same-type constraint that maps a potential
     /// archetype in this equivalence class to a concrete type along with

lib/AST/GenericSignatureBuilder.cpp

@@ -1710,7 +1710,7 @@ bool EquivalenceClass::recordConformanceConstraint(
                                  GenericSignatureBuilder &builder,
                                  ResolvedType type,
                                  ProtocolDecl *proto,
-                                 FloatingRequirementSource source) {
+                                 const RequirementSource *source) {
   // If we haven't seen a conformance to this protocol yet, add it.
   bool inserted = false;
   auto known = conformsTo.find(proto);
@@ -1730,8 +1730,7 @@ bool EquivalenceClass::recordConformanceConstraint(
   }
 
   // Record this conformance source.
-  known->second.push_back({type.getUnresolvedType(), proto,
-                           source.getSource(builder, type)});
+  known->second.push_back({type.getUnresolvedType(), proto, source});
   ++NumConformanceConstraints;
 
   return inserted;
@@ -4167,13 +4166,15 @@ ConstraintResult GenericSignatureBuilder::addConformanceRequirement(
                                ResolvedType type,
                                ProtocolDecl *proto,
                                FloatingRequirementSource source) {
+  auto resolvedSource = source.getSource(*this, type);
+
   // Add the conformance requirement, bailing out earlier if we've already
   // seen it.
   auto equivClass = type.getEquivalenceClass(*this);
-  if (!equivClass->recordConformanceConstraint(*this, type, proto, source))
+  if (!equivClass->recordConformanceConstraint(*this, type, proto,
+                                               resolvedSource))
     return ConstraintResult::Resolved;
 
-  auto resolvedSource = source.getSource(*this, type);
   return expandConformanceRequirement(type, proto, resolvedSource,
                                       /*onlySameTypeRequirements=*/false);
 }
@@ -4325,7 +4326,7 @@ ConstraintResult GenericSignatureBuilder::addSuperclassRequirementDirect(
   ++NumSuperclassConstraints;
 
   // Update the equivalence class with the constraint.
-  if (!updateSuperclass(type, superclass, source))
+  if (!updateSuperclass(type, superclass, resolvedSource))
     ++NumSuperclassConstraintsExtra;
 
   return ConstraintResult::Resolved;