Fixes off-by-one error; rename method

internal/gps/identifier.go

@@ -217,6 +217,9 @@ type completeDep struct {
 	pl []string
 }
 
+// dependency represents an incomplete edge in the depgraph. It has a
+// fully-realized atom as the depender (the tail/source of the edge), and a set
+// of requirements that any atom to be attached at the head/target must satisfy.
 type dependency struct {
 	depender atom
 	dep      completeDep

internal/gps/satisfy.go

@@ -54,7 +54,7 @@ func (s *solver) check(a atomWithPackages, pkgonly bool) error {
 		if err = s.checkIdentMatches(a, dep); err != nil {
 			return err
 		}
-		if err = s.checkCaseConflicts(a, dep); err != nil {
+		if err = s.checkRootCaseConflicts(a, dep); err != nil {
 			return err
 		}
 		if err = s.checkDepsConstraintsAllowable(a, dep); err != nil {
@@ -221,19 +221,19 @@ func (s *solver) checkIdentMatches(a atomWithPackages, cdep completeDep) error {
 	return nil
 }
 
-// checkCaseConflicts ensures that the ProjectRoot specified in the completeDep
+// checkRootCaseConflicts ensures that the ProjectRoot specified in the completeDep
 // does not have case conflicts with any existing dependencies.
 //
 // We only need to check the ProjectRoot, rather than any packages therein, as
 // the later check for package existence is case-sensitive.
-func (s *solver) checkCaseConflicts(a atomWithPackages, cdep completeDep) error {
+func (s *solver) checkRootCaseConflicts(a atomWithPackages, cdep completeDep) error {
 	pr := cdep.workingConstraint.Ident.ProjectRoot
 	hasConflict, current := s.sel.findCaseConflicts(pr)
 	if !hasConflict {
 		return nil
 	}
 
-	curid, _ := s.sel.getIdentFor(pr)
+	curid, _ := s.sel.getIdentFor(current)
 	deps := s.sel.getDependenciesOn(curid)
 	for _, d := range deps {
 		s.fail(d.depender.id)

internal/gps/selection.go

@@ -83,11 +83,11 @@ func (s *selection) findCaseConflicts(pr ProjectRoot) (bool, ProjectRoot) {
 func (s *selection) pushDep(dep dependency) {
 	pr := dep.dep.Ident.ProjectRoot
 	deps := s.deps[pr]
-	s.deps[pr] = append(deps, dep)
-
-	if len(deps) == 1 {
+	if len(deps) == 0 {
 		s.foldRoots[toFold(string(pr))] = pr
 	}
+
+	s.deps[pr] = append(deps, dep)
 }
 
 func (s *selection) popDep(id ProjectIdentifier) (dep dependency) {