transform: restore previous test behavior

I think it's much nicer to have the test output inline in the source
file, that way it's much easier to review any changes. For example, when
escape analysis is improved this is visible with removed `// OUT` lines.

This is similar to how LLVM writes its tests, and I like that style.

transform/allocs_test.go

@@ -1,7 +1,9 @@
 package transform_test
 
 import (
+	"fmt"
 	"go/token"
+	"os"
 	"regexp"
 	"sort"
 	"strings"
@@ -49,23 +51,37 @@ func TestAllocs2(t *testing.T) {
 	})
 	sort.Slice(reports, func(i, j int) bool { return reports[i].pos.Line < reports[j].pos.Line })
 
-	// Render every report in each format and diff against its golden file.
-	for _, format := range []struct {
-		name   string
-		render func(report) string
-	}{
-		{"reason", func(r report) string { return transform.FormatAllocReason(r.pos, r.reason) }},
-		{"cover", func(r report) string { return transform.FormatAllocCover(r.pos) }},
-	} {
-		t.Run(format.name, func(t *testing.T) {
-			var got strings.Builder
-			for _, r := range reports {
-				if line := format.render(r); line != "" {
-					got.WriteString(line)
-					got.WriteByte('\n')
-				}
-			}
-			checkGolden(t, goldenFile+"."+format.name, got.String())
-		})
+	// Load expected test output (the OUT: lines).
+	testInput, err := os.ReadFile("./testdata/allocs2.go")
+	if err != nil {
+		t.Fatal("could not read test input:", err)
 	}
+	var expectedTestOutput strings.Builder
+	for i, line := range strings.Split(strings.ReplaceAll(string(testInput), "\r\n", "\n"), "\n") {
+		const prefix = " // OUT: "
+		if idx := strings.Index(line, prefix); idx > 0 {
+			msg := line[idx+len(prefix):]
+			fmt.Fprintf(&expectedTestOutput, "allocs2.go:%d: %s\n", i+1, msg)
+		}
+	}
+
+	// Check whether the '// OUT' lines in allocs2.go match with the output we
+	// got from the test.
+	var actualTestOutput strings.Builder
+	for _, r := range reports {
+		fmt.Fprintf(&actualTestOutput, "allocs2.go:%d: %s\n", r.pos.Line, r.reason)
+	}
+	if actualTestOutput.String() != expectedTestOutput.String() {
+		t.Errorf("expected:\n%s\nactual:\n%s", expectedTestOutput.String(), actualTestOutput.String())
+	}
+
+	// Render the cover report and diff it against its golden file.
+	var got strings.Builder
+	for _, r := range reports {
+		if line := transform.FormatAllocCover(r.pos); line != "" {
+			got.WriteString(line)
+			got.WriteByte('\n')
+		}
+	}
+	checkGolden(t, goldenFile+".cover", got.String())
 }

transform/testdata/allocs2.go

@@ -21,19 +21,19 @@ func main() {
 	s3 := make([]int, 3)
 	returnIntSlice(s3)
 
-	useSlice(make([]int, getUnknownNumber()))
+	useSlice(make([]int, getUnknownNumber())) // OUT: size is not constant
 
-	s4 := make([]byte, 300)
+	s4 := make([]byte, 300) // OUT: object size 300 exceeds maximum stack allocation size 256
 	readByteSlice(s4)
 
-	s5 := make([]int, 4)
+	s5 := make([]int, 4) // OUT: escapes at line 30
 	_ = append(s5, 5)
 
 	s6 := make([]int, 3)
 	s7 := []int{1, 2, 3}
 	copySlice(s6, s7)
 
-	c1 := getComplex128()
+	c1 := getComplex128() // OUT: escapes at line 37
 	useInterface(c1)
 
 	n3 := 5
@@ -41,13 +41,13 @@ func main() {
 		return n3
 	}()
 
-	callVariadic(3, 5, 8)
+	callVariadic(3, 5, 8) // OUT: escapes at line 44
 
-	s8 := []int{3, 5, 8}
+	s8 := []int{3, 5, 8} // OUT: escapes at line 47
 	callVariadic(s8...)
 
-	n4 := 3
-	n5 := 7
+	n4 := 3 // OUT: escapes at line 51
+	n5 := 7 // OUT: escapes at line 51
 	func() {
 		n4 = n5
 	}()
@@ -104,14 +104,14 @@ func nonEscapingReturnedPointer() vector3 {
 var escapedSlice []int
 
 func escapingReturnedSlice() {
-	s := make([]int, 3)
+	s := make([]int, 3) // OUT: escapes at line 108
 	escapedSlice = returnIntSlice(s)
 }
 
 var escapedVector3 *vector3
 
 func escapingReturnedPointer() {
-	b := vector3{4, 5, 6}
+	b := vector3{4, 5, 6} // OUT: escapes at line 117
 
 	c := scaleVector3(&b, 0.5)
 	escapedVector3 = c
@@ -125,7 +125,7 @@ func recursiveScaleVector3(vec *vector3, n int) *vector3 {
 }
 
 func recursiveReturnedPointer() vector3 {
-	b := vector3{4, 5, 6}
+	b := vector3{4, 5, 6} // OUT: escapes at unknown line
 
 	c := recursiveScaleVector3(&b, 1)
 	return *c

transform/testdata/allocs2.out.cover

@@ -1,11 +1,11 @@
-testdata/allocs2.go:24.1,24.43 1 0
-testdata/allocs2.go:26.1,26.25 1 0
-testdata/allocs2.go:29.1,29.22 1 0
-testdata/allocs2.go:36.1,36.23 1 0
-testdata/allocs2.go:44.1,44.23 1 0
-testdata/allocs2.go:46.1,46.22 1 0
-testdata/allocs2.go:49.1,49.9 1 0
-testdata/allocs2.go:50.1,50.9 1 0
-testdata/allocs2.go:107.1,107.21 1 0
-testdata/allocs2.go:114.1,114.23 1 0
-testdata/allocs2.go:128.1,128.23 1 0
+testdata/allocs2.go:24.1,24.72 1 0
+testdata/allocs2.go:26.1,26.91 1 0
+testdata/allocs2.go:29.1,29.49 1 0
+testdata/allocs2.go:36.1,36.50 1 0
+testdata/allocs2.go:44.1,44.50 1 0
+testdata/allocs2.go:46.1,46.49 1 0
+testdata/allocs2.go:49.1,49.36 1 0
+testdata/allocs2.go:50.1,50.36 1 0
+testdata/allocs2.go:107.1,107.49 1 0
+testdata/allocs2.go:114.1,114.51 1 0
+testdata/allocs2.go:128.1,128.55 1 0

transform/testdata/allocs2.out.reason

@@ -1,11 +0,0 @@
-testdata/allocs2.go:24:15: object allocated on the heap: size is not constant
-testdata/allocs2.go:26:12: object allocated on the heap: object size 300 exceeds maximum stack allocation size 256
-testdata/allocs2.go:29:12: object allocated on the heap: escapes at line 30
-testdata/allocs2.go:36:21: object allocated on the heap: escapes at line 37
-testdata/allocs2.go:44:22: object allocated on the heap: escapes at line 44
-testdata/allocs2.go:46:13: object allocated on the heap: escapes at line 47
-testdata/allocs2.go:49:2: object allocated on the heap: escapes at line 51
-testdata/allocs2.go:50:2: object allocated on the heap: escapes at line 51
-testdata/allocs2.go:107:11: object allocated on the heap: escapes at line 108
-testdata/allocs2.go:114:2: object allocated on the heap: escapes at line 117
-testdata/allocs2.go:128:2: object allocated on the heap: escapes at unknown line