Use generics for DepSets

Use Go's generics for DepSets so they don't require a type-specific
wrapper and reflection.

Test: depsets_test.go
Change-Id: I22ba0b7d680d37d2cd05230b0f560d166c4dd20b
diff --git a/android/depset_test.go b/android/depset_test.go
index 955ccb0..376dffa 100644
--- a/android/depset_test.go
+++ b/android/depset_test.go
@@ -17,51 +17,40 @@
 import (
 	"fmt"
 	"reflect"
-	"strconv"
 	"strings"
 	"testing"
 )
 
 func ExampleDepSet_ToList_postordered() {
-	a := NewDepSetBuilder(POSTORDER).Direct(PathForTesting("a")).Build()
-	b := NewDepSetBuilder(POSTORDER).Direct(PathForTesting("b")).Transitive(a).Build()
-	c := NewDepSetBuilder(POSTORDER).Direct(PathForTesting("c")).Transitive(a).Build()
-	d := NewDepSetBuilder(POSTORDER).Direct(PathForTesting("d")).Transitive(b, c).Build()
+	a := NewDepSetBuilder[Path](POSTORDER).Direct(PathForTesting("a")).Build()
+	b := NewDepSetBuilder[Path](POSTORDER).Direct(PathForTesting("b")).Transitive(a).Build()
+	c := NewDepSetBuilder[Path](POSTORDER).Direct(PathForTesting("c")).Transitive(a).Build()
+	d := NewDepSetBuilder[Path](POSTORDER).Direct(PathForTesting("d")).Transitive(b, c).Build()
 
-	fmt.Println(d.ToList().Strings())
+	fmt.Println(Paths(d.ToList()).Strings())
 	// Output: [a b c d]
 }
 
 func ExampleDepSet_ToList_preordered() {
-	a := NewDepSetBuilder(PREORDER).Direct(PathForTesting("a")).Build()
-	b := NewDepSetBuilder(PREORDER).Direct(PathForTesting("b")).Transitive(a).Build()
-	c := NewDepSetBuilder(PREORDER).Direct(PathForTesting("c")).Transitive(a).Build()
-	d := NewDepSetBuilder(PREORDER).Direct(PathForTesting("d")).Transitive(b, c).Build()
+	a := NewDepSetBuilder[Path](PREORDER).Direct(PathForTesting("a")).Build()
+	b := NewDepSetBuilder[Path](PREORDER).Direct(PathForTesting("b")).Transitive(a).Build()
+	c := NewDepSetBuilder[Path](PREORDER).Direct(PathForTesting("c")).Transitive(a).Build()
+	d := NewDepSetBuilder[Path](PREORDER).Direct(PathForTesting("d")).Transitive(b, c).Build()
 
-	fmt.Println(d.ToList().Strings())
+	fmt.Println(Paths(d.ToList()).Strings())
 	// Output: [d b a c]
 }
 
 func ExampleDepSet_ToList_topological() {
-	a := NewDepSetBuilder(TOPOLOGICAL).Direct(PathForTesting("a")).Build()
-	b := NewDepSetBuilder(TOPOLOGICAL).Direct(PathForTesting("b")).Transitive(a).Build()
-	c := NewDepSetBuilder(TOPOLOGICAL).Direct(PathForTesting("c")).Transitive(a).Build()
-	d := NewDepSetBuilder(TOPOLOGICAL).Direct(PathForTesting("d")).Transitive(b, c).Build()
+	a := NewDepSetBuilder[Path](TOPOLOGICAL).Direct(PathForTesting("a")).Build()
+	b := NewDepSetBuilder[Path](TOPOLOGICAL).Direct(PathForTesting("b")).Transitive(a).Build()
+	c := NewDepSetBuilder[Path](TOPOLOGICAL).Direct(PathForTesting("c")).Transitive(a).Build()
+	d := NewDepSetBuilder[Path](TOPOLOGICAL).Direct(PathForTesting("d")).Transitive(b, c).Build()
 
-	fmt.Println(d.ToList().Strings())
+	fmt.Println(Paths(d.ToList()).Strings())
 	// Output: [d b c a]
 }
 
-func ExampleDepSet_ToSortedList() {
-	a := NewDepSetBuilder(POSTORDER).Direct(PathForTesting("a")).Build()
-	b := NewDepSetBuilder(POSTORDER).Direct(PathForTesting("b")).Transitive(a).Build()
-	c := NewDepSetBuilder(POSTORDER).Direct(PathForTesting("c")).Transitive(a).Build()
-	d := NewDepSetBuilder(POSTORDER).Direct(PathForTesting("d")).Transitive(b, c).Build()
-
-	fmt.Println(d.ToSortedList().Strings())
-	// Output: [a b c d]
-}
-
 // Tests based on Bazel's ExpanderTestBase.java to ensure compatibility
 // https://github.com/bazelbuild/bazel/blob/master/src/test/java/com/google/devtools/build/lib/collect/nestedset/ExpanderTestBase.java
 func TestDepSet(t *testing.T) {
@@ -74,13 +63,13 @@
 
 	tests := []struct {
 		name                             string
-		depSet                           func(t *testing.T, order DepSetOrder) *DepSet
+		depSet                           func(t *testing.T, order DepSetOrder) *DepSet[Path]
 		postorder, preorder, topological []string
 	}{
 		{
 			name: "simple",
-			depSet: func(t *testing.T, order DepSetOrder) *DepSet {
-				return NewDepSet(order, Paths{c, a, b}, nil)
+			depSet: func(t *testing.T, order DepSetOrder) *DepSet[Path] {
+				return NewDepSet[Path](order, Paths{c, a, b}, nil)
 			},
 			postorder:   []string{"c", "a", "b"},
 			preorder:    []string{"c", "a", "b"},
@@ -88,8 +77,8 @@
 		},
 		{
 			name: "simpleNoDuplicates",
-			depSet: func(t *testing.T, order DepSetOrder) *DepSet {
-				return NewDepSet(order, Paths{c, a, a, a, b}, nil)
+			depSet: func(t *testing.T, order DepSetOrder) *DepSet[Path] {
+				return NewDepSet[Path](order, Paths{c, a, a, a, b}, nil)
 			},
 			postorder:   []string{"c", "a", "b"},
 			preorder:    []string{"c", "a", "b"},
@@ -97,9 +86,9 @@
 		},
 		{
 			name: "nesting",
-			depSet: func(t *testing.T, order DepSetOrder) *DepSet {
-				subset := NewDepSet(order, Paths{c, a, e}, nil)
-				return NewDepSet(order, Paths{b, d}, []*DepSet{subset})
+			depSet: func(t *testing.T, order DepSetOrder) *DepSet[Path] {
+				subset := NewDepSet[Path](order, Paths{c, a, e}, nil)
+				return NewDepSet[Path](order, Paths{b, d}, []*DepSet[Path]{subset})
 			},
 			postorder:   []string{"c", "a", "e", "b", "d"},
 			preorder:    []string{"b", "d", "c", "a", "e"},
@@ -107,14 +96,14 @@
 		},
 		{
 			name: "builderReuse",
-			depSet: func(t *testing.T, order DepSetOrder) *DepSet {
+			depSet: func(t *testing.T, order DepSetOrder) *DepSet[Path] {
 				assertEquals := func(t *testing.T, w, g Paths) {
 					t.Helper()
 					if !reflect.DeepEqual(w, g) {
 						t.Errorf("want %q, got %q", w, g)
 					}
 				}
-				builder := NewDepSetBuilder(order)
+				builder := NewDepSetBuilder[Path](order)
 				assertEquals(t, nil, builder.Build().ToList())
 
 				builder.Direct(b)
@@ -123,7 +112,7 @@
 				builder.Direct(d)
 				assertEquals(t, Paths{b, d}, builder.Build().ToList())
 
-				child := NewDepSetBuilder(order).Direct(c, a, e).Build()
+				child := NewDepSetBuilder[Path](order).Direct(c, a, e).Build()
 				builder.Transitive(child)
 				return builder.Build()
 			},
@@ -133,9 +122,9 @@
 		},
 		{
 			name: "builderChaining",
-			depSet: func(t *testing.T, order DepSetOrder) *DepSet {
-				return NewDepSetBuilder(order).Direct(b).Direct(d).
-					Transitive(NewDepSetBuilder(order).Direct(c, a, e).Build()).Build()
+			depSet: func(t *testing.T, order DepSetOrder) *DepSet[Path] {
+				return NewDepSetBuilder[Path](order).Direct(b).Direct(d).
+					Transitive(NewDepSetBuilder[Path](order).Direct(c, a, e).Build()).Build()
 			},
 			postorder:   []string{"c", "a", "e", "b", "d"},
 			preorder:    []string{"b", "d", "c", "a", "e"},
@@ -143,9 +132,9 @@
 		},
 		{
 			name: "transitiveDepsHandledSeparately",
-			depSet: func(t *testing.T, order DepSetOrder) *DepSet {
-				subset := NewDepSetBuilder(order).Direct(c, a, e).Build()
-				builder := NewDepSetBuilder(order)
+			depSet: func(t *testing.T, order DepSetOrder) *DepSet[Path] {
+				subset := NewDepSetBuilder[Path](order).Direct(c, a, e).Build()
+				builder := NewDepSetBuilder[Path](order)
 				// The fact that we add the transitive subset between the Direct(b) and Direct(d)
 				// calls should not change the result.
 				builder.Direct(b)
@@ -159,9 +148,9 @@
 		},
 		{
 			name: "nestingNoDuplicates",
-			depSet: func(t *testing.T, order DepSetOrder) *DepSet {
-				subset := NewDepSetBuilder(order).Direct(c, a, e).Build()
-				return NewDepSetBuilder(order).Direct(b, d, e).Transitive(subset).Build()
+			depSet: func(t *testing.T, order DepSetOrder) *DepSet[Path] {
+				subset := NewDepSetBuilder[Path](order).Direct(c, a, e).Build()
+				return NewDepSetBuilder[Path](order).Direct(b, d, e).Transitive(subset).Build()
 			},
 			postorder:   []string{"c", "a", "e", "b", "d"},
 			preorder:    []string{"b", "d", "e", "c", "a"},
@@ -169,10 +158,10 @@
 		},
 		{
 			name: "chain",
-			depSet: func(t *testing.T, order DepSetOrder) *DepSet {
-				c := NewDepSetBuilder(order).Direct(c).Build()
-				b := NewDepSetBuilder(order).Direct(b).Transitive(c).Build()
-				a := NewDepSetBuilder(order).Direct(a).Transitive(b).Build()
+			depSet: func(t *testing.T, order DepSetOrder) *DepSet[Path] {
+				c := NewDepSetBuilder[Path](order).Direct(c).Build()
+				b := NewDepSetBuilder[Path](order).Direct(b).Transitive(c).Build()
+				a := NewDepSetBuilder[Path](order).Direct(a).Transitive(b).Build()
 
 				return a
 			},
@@ -182,11 +171,11 @@
 		},
 		{
 			name: "diamond",
-			depSet: func(t *testing.T, order DepSetOrder) *DepSet {
-				d := NewDepSetBuilder(order).Direct(d).Build()
-				c := NewDepSetBuilder(order).Direct(c).Transitive(d).Build()
-				b := NewDepSetBuilder(order).Direct(b).Transitive(d).Build()
-				a := NewDepSetBuilder(order).Direct(a).Transitive(b).Transitive(c).Build()
+			depSet: func(t *testing.T, order DepSetOrder) *DepSet[Path] {
+				d := NewDepSetBuilder[Path](order).Direct(d).Build()
+				c := NewDepSetBuilder[Path](order).Direct(c).Transitive(d).Build()
+				b := NewDepSetBuilder[Path](order).Direct(b).Transitive(d).Build()
+				a := NewDepSetBuilder[Path](order).Direct(a).Transitive(b).Transitive(c).Build()
 
 				return a
 			},
@@ -196,12 +185,12 @@
 		},
 		{
 			name: "extendedDiamond",
-			depSet: func(t *testing.T, order DepSetOrder) *DepSet {
-				d := NewDepSetBuilder(order).Direct(d).Build()
-				e := NewDepSetBuilder(order).Direct(e).Build()
-				b := NewDepSetBuilder(order).Direct(b).Transitive(d).Transitive(e).Build()
-				c := NewDepSetBuilder(order).Direct(c).Transitive(e).Transitive(d).Build()
-				a := NewDepSetBuilder(order).Direct(a).Transitive(b).Transitive(c).Build()
+			depSet: func(t *testing.T, order DepSetOrder) *DepSet[Path] {
+				d := NewDepSetBuilder[Path](order).Direct(d).Build()
+				e := NewDepSetBuilder[Path](order).Direct(e).Build()
+				b := NewDepSetBuilder[Path](order).Direct(b).Transitive(d).Transitive(e).Build()
+				c := NewDepSetBuilder[Path](order).Direct(c).Transitive(e).Transitive(d).Build()
+				a := NewDepSetBuilder[Path](order).Direct(a).Transitive(b).Transitive(c).Build()
 				return a
 			},
 			postorder:   []string{"d", "e", "b", "c", "a"},
@@ -210,13 +199,13 @@
 		},
 		{
 			name: "extendedDiamondRightArm",
-			depSet: func(t *testing.T, order DepSetOrder) *DepSet {
-				d := NewDepSetBuilder(order).Direct(d).Build()
-				e := NewDepSetBuilder(order).Direct(e).Build()
-				b := NewDepSetBuilder(order).Direct(b).Transitive(d).Transitive(e).Build()
-				c2 := NewDepSetBuilder(order).Direct(c2).Transitive(e).Transitive(d).Build()
-				c := NewDepSetBuilder(order).Direct(c).Transitive(c2).Build()
-				a := NewDepSetBuilder(order).Direct(a).Transitive(b).Transitive(c).Build()
+			depSet: func(t *testing.T, order DepSetOrder) *DepSet[Path] {
+				d := NewDepSetBuilder[Path](order).Direct(d).Build()
+				e := NewDepSetBuilder[Path](order).Direct(e).Build()
+				b := NewDepSetBuilder[Path](order).Direct(b).Transitive(d).Transitive(e).Build()
+				c2 := NewDepSetBuilder[Path](order).Direct(c2).Transitive(e).Transitive(d).Build()
+				c := NewDepSetBuilder[Path](order).Direct(c).Transitive(c2).Build()
+				a := NewDepSetBuilder[Path](order).Direct(a).Transitive(b).Transitive(c).Build()
 				return a
 			},
 			postorder:   []string{"d", "e", "b", "c2", "c", "a"},
@@ -225,10 +214,10 @@
 		},
 		{
 			name: "orderConflict",
-			depSet: func(t *testing.T, order DepSetOrder) *DepSet {
-				child1 := NewDepSetBuilder(order).Direct(a, b).Build()
-				child2 := NewDepSetBuilder(order).Direct(b, a).Build()
-				parent := NewDepSetBuilder(order).Transitive(child1).Transitive(child2).Build()
+			depSet: func(t *testing.T, order DepSetOrder) *DepSet[Path] {
+				child1 := NewDepSetBuilder[Path](order).Direct(a, b).Build()
+				child2 := NewDepSetBuilder[Path](order).Direct(b, a).Build()
+				parent := NewDepSetBuilder[Path](order).Transitive(child1).Transitive(child2).Build()
 				return parent
 			},
 			postorder:   []string{"a", "b"},
@@ -237,12 +226,12 @@
 		},
 		{
 			name: "orderConflictNested",
-			depSet: func(t *testing.T, order DepSetOrder) *DepSet {
-				a := NewDepSetBuilder(order).Direct(a).Build()
-				b := NewDepSetBuilder(order).Direct(b).Build()
-				child1 := NewDepSetBuilder(order).Transitive(a).Transitive(b).Build()
-				child2 := NewDepSetBuilder(order).Transitive(b).Transitive(a).Build()
-				parent := NewDepSetBuilder(order).Transitive(child1).Transitive(child2).Build()
+			depSet: func(t *testing.T, order DepSetOrder) *DepSet[Path] {
+				a := NewDepSetBuilder[Path](order).Direct(a).Build()
+				b := NewDepSetBuilder[Path](order).Direct(b).Build()
+				child1 := NewDepSetBuilder[Path](order).Transitive(a).Transitive(b).Build()
+				child2 := NewDepSetBuilder[Path](order).Transitive(b).Transitive(a).Build()
+				parent := NewDepSetBuilder[Path](order).Transitive(child1).Transitive(child2).Build()
 				return parent
 			},
 			postorder:   []string{"a", "b"},
@@ -255,19 +244,19 @@
 		t.Run(tt.name, func(t *testing.T) {
 			t.Run("postorder", func(t *testing.T) {
 				depSet := tt.depSet(t, POSTORDER)
-				if g, w := depSet.ToList().Strings(), tt.postorder; !reflect.DeepEqual(g, w) {
+				if g, w := Paths(depSet.ToList()).Strings(), tt.postorder; !reflect.DeepEqual(g, w) {
 					t.Errorf("expected ToList() = %q, got %q", w, g)
 				}
 			})
 			t.Run("preorder", func(t *testing.T) {
 				depSet := tt.depSet(t, PREORDER)
-				if g, w := depSet.ToList().Strings(), tt.preorder; !reflect.DeepEqual(g, w) {
+				if g, w := Paths(depSet.ToList()).Strings(), tt.preorder; !reflect.DeepEqual(g, w) {
 					t.Errorf("expected ToList() = %q, got %q", w, g)
 				}
 			})
 			t.Run("topological", func(t *testing.T) {
 				depSet := tt.depSet(t, TOPOLOGICAL)
-				if g, w := depSet.ToList().Strings(), tt.topological; !reflect.DeepEqual(g, w) {
+				if g, w := Paths(depSet.ToList()).Strings(), tt.topological; !reflect.DeepEqual(g, w) {
 					t.Errorf("expected ToList() = %q, got %q", w, g)
 				}
 			})
@@ -288,7 +277,7 @@
 				}
 			}
 		}()
-		NewDepSet(order1, nil, []*DepSet{NewDepSet(order2, nil, nil)})
+		NewDepSet(order1, nil, []*DepSet[Path]{NewDepSet[Path](order2, nil, nil)})
 		t.Fatal("expected panic")
 	}
 
@@ -304,87 +293,3 @@
 		})
 	}
 }
-
-func Test_firstUnique(t *testing.T) {
-	f := func(t *testing.T, imp func([]string) []string, in, want []string) {
-		t.Helper()
-		out := imp(in)
-		if !reflect.DeepEqual(out, want) {
-			t.Errorf("incorrect output:")
-			t.Errorf("     input: %#v", in)
-			t.Errorf("  expected: %#v", want)
-			t.Errorf("       got: %#v", out)
-		}
-	}
-
-	for _, testCase := range firstUniqueStringsTestCases {
-		t.Run("list", func(t *testing.T) {
-			f(t, func(s []string) []string {
-				return firstUniqueList(s).([]string)
-			}, testCase.in, testCase.out)
-		})
-		t.Run("map", func(t *testing.T) {
-			f(t, func(s []string) []string {
-				return firstUniqueMap(s).([]string)
-			}, testCase.in, testCase.out)
-		})
-	}
-}
-
-func Benchmark_firstUnique(b *testing.B) {
-	implementations := []struct {
-		name string
-		f    func([]string) []string
-	}{
-		{
-			name: "list",
-			f: func(slice []string) []string {
-				return firstUniqueList(slice).([]string)
-			},
-		},
-		{
-			name: "map",
-			f: func(slice []string) []string {
-				return firstUniqueMap(slice).([]string)
-			},
-		},
-		{
-			name: "optimal",
-			f: func(slice []string) []string {
-				return firstUnique(slice).([]string)
-			},
-		},
-	}
-	const maxSize = 1024
-	uniqueStrings := make([]string, maxSize)
-	for i := range uniqueStrings {
-		uniqueStrings[i] = strconv.Itoa(i)
-	}
-	sameString := make([]string, maxSize)
-	for i := range sameString {
-		sameString[i] = uniqueStrings[0]
-	}
-
-	f := func(b *testing.B, imp func([]string) []string, s []string) {
-		for i := 0; i < b.N; i++ {
-			b.ReportAllocs()
-			s = append([]string(nil), s...)
-			imp(s)
-		}
-	}
-
-	for n := 1; n <= maxSize; n <<= 1 {
-		b.Run(strconv.Itoa(n), func(b *testing.B) {
-			for _, implementation := range implementations {
-				b.Run(implementation.name, func(b *testing.B) {
-					b.Run("same", func(b *testing.B) {
-						f(b, implementation.f, sameString[:n])
-					})
-					b.Run("unique", func(b *testing.B) {
-						f(b, implementation.f, uniqueStrings[:n])
-					})
-				})
-			}
-		})
-	}
-}