go/types, types2: avoid sorting all errors when matching errors

Sorting is only needed if there are multiple matching errors on
the same line. Instead, in that rare case, select the error that
is closest.

Follow-up on CL 456137.

Change-Id: Ia2056b21c629f3a42495e32de89607fbefb82fa7
Reviewed-on: https://go-review.googlesource.com/c/go/+/456335
Run-TryBot: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>

src/cmd/compile/internal/types2/check_test.go

@@ -31,7 +31,6 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
-	"sort"
 	"strings"
 	"testing"
 
@@ -68,8 +67,8 @@ func unpackError(err error) (syntax.Pos, string) {
 	}
 }
 
-// delta returns the absolute difference between x and y.
+// absDiff returns the absolute difference between x and y.
-func delta(x, y uint) uint {
+func absDiff(x, y uint) uint {
 	if x < y {
 		return y - x
 	}
@@ -165,13 +164,6 @@ func testFiles(t *testing.T, filenames []string, colDelta uint, manual bool) {
 		return
 	}
 
-	// sort errlist in source order
-	sort.Slice(errlist, func(i, j int) bool {
-		pi, _ := unpackError(errlist[i])
-		pj, _ := unpackError(errlist[j])
-		return pi.Cmp(pj) < 0
-	})
-
 	// collect expected errors
 	errmap := make(map[string]map[uint][]syntax.Error)
 	for _, filename := range filenames {
@@ -187,6 +179,7 @@ func testFiles(t *testing.T, filenames []string, colDelta uint, manual bool) {
 	}
 
 	// match against found errors
+	var indices []int // list indices of matching errors, reused for each error
 	for _, err := range errlist {
 		gotPos, gotMsg := unpackError(err)
 
@@ -199,8 +192,8 @@ func testFiles(t *testing.T, filenames []string, colDelta uint, manual bool) {
 			errList = filemap[line]
 		}
 
-		// one of errors in errList should match the current error
+		// At least one of the errors in errList should match the current error.
-		index := -1 // errList index of matching message, if any
+		indices = indices[:0]
 		for i, want := range errList {
 			pattern := strings.TrimSpace(want.Msg[len(" ERROR "):])
 			if n := len(pattern); n >= 2 && pattern[0] == '"' && pattern[n-1] == '"' {
@@ -212,19 +205,27 @@ func testFiles(t *testing.T, filenames []string, colDelta uint, manual bool) {
 				continue
 			}
 			if rx.MatchString(gotMsg) {
-				index = i
+				indices = append(indices, i)
-				break
 			}
 		}
-		if index < 0 {
+		if len(indices) == 0 {
 			t.Errorf("%s: no error expected: %q", gotPos, gotMsg)
 			continue
 		}
+		// len(indices) > 0
 
-		// column position must be within expected colDelta
+		// If there are multiple matching errors, select the one with the closest column position.
-		want := errList[index]
+		index := -1 // index of matching error
-		if delta(gotPos.Col(), want.Pos.Col()) > colDelta {
+		var delta uint
-			t.Errorf("%s: got col = %d; want %d", gotPos, gotPos.Col(), want.Pos.Col())
+		for _, i := range indices {
+			if d := absDiff(gotPos.Col(), errList[i].Pos.Col()); index < 0 || d < delta {
+				index, delta = i, d
+			}
+		}
+
+		// The closest column position must be within expected colDelta.
+		if delta > colDelta {
+			t.Errorf("%s: got col = %d; want %d", gotPos, gotPos.Col(), errList[index].Pos.Col())
 		}
 
 		// eliminate from errList

src/go/types/check_test.go

@@ -36,7 +36,6 @@ import (
 	"path/filepath"
 	"reflect"
 	"regexp"
-	"sort"
 	"strings"
 	"testing"
 
@@ -82,8 +81,8 @@ func unpackError(fset *token.FileSet, err error) (token.Position, string) {
 	panic("unreachable")
 }
 
-// delta returns the absolute difference between x and y.
+// absDiff returns the absolute difference between x and y.
-func delta(x, y int) int {
+func absDiff(x, y int) int {
 	if x < y {
 		return y - x
 	}
@@ -183,20 +182,6 @@ func testFiles(t *testing.T, sizes Sizes, filenames []string, srcs [][]byte, man
 		return
 	}
 
-	// sort errlist in source order
-	sort.Slice(errlist, func(i, j int) bool {
-		// TODO(gri) This is not correct as scanner.Errors
-		// don't have a correctly set Offset. But we only
-		// care about sorting when multiple equal errors
-		// appear on the same line, which happens with some
-		// type checker errors.
-		// For now this works. Will remove need for sorting
-		// in a subsequent CL.
-		pi, _ := unpackError(fset, errlist[i])
-		pj, _ := unpackError(fset, errlist[j])
-		return pi.Offset < pj.Offset
-	})
-
 	// collect expected errors
 	errmap := make(map[string]map[int][]comment)
 	for i, filename := range filenames {
@@ -206,6 +191,7 @@ func testFiles(t *testing.T, sizes Sizes, filenames []string, srcs [][]byte, man
 	}
 
 	// match against found errors
+	var indices []int // list indices of matching errors, reused for each error
 	for _, err := range errlist {
 		gotPos, gotMsg := unpackError(fset, err)
 
@@ -218,8 +204,8 @@ func testFiles(t *testing.T, sizes Sizes, filenames []string, srcs [][]byte, man
 			errList = filemap[line]
 		}
 
-		// one of errors in errList should match the current error
+		// At least one of the errors in errList should match the current error.
-		index := -1 // errList index of matching message, if any
+		indices = indices[:0]
 		for i, want := range errList {
 			pattern := strings.TrimSpace(want.text[len(" ERROR "):])
 			if n := len(pattern); n >= 2 && pattern[0] == '"' && pattern[n-1] == '"' {
@@ -231,20 +217,28 @@ func testFiles(t *testing.T, sizes Sizes, filenames []string, srcs [][]byte, man
 				continue
 			}
 			if rx.MatchString(gotMsg) {
-				index = i
+				indices = append(indices, i)
-				break
 			}
 		}
-		if index < 0 {
+		if len(indices) == 0 {
 			t.Errorf("%s: no error expected: %q", gotPos, gotMsg)
 			continue
 		}
+		// len(indices) > 0
 
-		// column position must be within expected colDelta
+		// If there are multiple matching errors, select the one with the closest column position.
-		const colDelta = 0
+		index := -1 // index of matching error
-		want := errList[index]
+		var delta int
-		if delta(gotPos.Column, want.col) > colDelta {
+		for _, i := range indices {
-			t.Errorf("%s: got col = %d; want %d", gotPos, gotPos.Column, want.col)
+			if d := absDiff(gotPos.Column, errList[i].col); index < 0 || d < delta {
+				index, delta = i, d
+			}
+		}
+
+		// The closest column position must be within expected colDelta.
+		const colDelta = 0 // go/types errors are positioned correctly
+		if delta > colDelta {
+			t.Errorf("%s: got col = %d; want %d", gotPos, gotPos.Column, errList[index].col)
 		}
 
 		// eliminate from errList