Revert "go/ast: fix SortImports to handle block comments"

This reverts CL 162337.

Reason for revert: this introduces a regression

Fixes #33538
Updates #18929

Change-Id: Ib2320a840c6d3ec7912e8f414e933d04fbf11ab4
Reviewed-on: https://go-review.googlesource.com/c/go/+/189379
Reviewed-by: Robert Griesemer <gri@golang.org>

3 files changed, 23 insertions, 180 deletions

diff --git a/src/cmd/gofmt/testdata/import.golden b/src/cmd/gofmt/testdata/import.golden
index f7d742e3e8..51d7be79df 100644
--- a/src/cmd/gofmt/testdata/import.golden
+++ b/src/cmd/gofmt/testdata/import.golden
@@ -1,4 +1,3 @@
-// package comment
 package main
 
 import (
@@ -21,10 +20,6 @@ import (
 	"io"
 )
 
-// We reset the line numbering to test that
-// the formatting works independent of line directives
-//line :19
-
 import (
 	"errors"
 	"fmt"
@@ -129,58 +124,3 @@ import (
 
 	"dedup_by_group"
 )
-
-import (
-	"fmt" // for Printf
-	/* comment */ io1 "io"
-	/* comment */ io2 "io"
-	/* comment */ "log"
-)
-
-import (
-	"fmt"
-	/* comment */ io1 "io"
-	/* comment */ io2 "io" // hello
-	"math"                 /* right side */
-	// end
-)
-
-import (
-	"errors" // for New
-	"fmt"
-	/* comment */ io1 "io" /* before */ // after
-	io2 "io"               // another
-	// end
-)
-
-import (
-	"errors" // for New
-	/* left */ "fmt" /* right */
-	"log"            // for Fatal
-	/* left */ "math" /* right */
-)
-
-import /* why */ /* comment here? */ (
-	/* comment */ "fmt"
-	"math"
-)
-
-// Reset it again
-//line :100
-
-// Dedup with different import styles
-import (
-	"path"
-	. "path"
-	_ "path"
-	pathpkg "path"
-)
-
-/* comment */
-import (
-	"fmt"
-	"math" // for Abs
-	// This is a new run
-	"errors"
-	"fmt"
-)
diff --git a/src/cmd/gofmt/testdata/import.input b/src/cmd/gofmt/testdata/import.input
index 6e3a3a3bed..9a4b09dbf9 100644
--- a/src/cmd/gofmt/testdata/import.input
+++ b/src/cmd/gofmt/testdata/import.input
@@ -1,4 +1,3 @@
-// package comment
 package main
 
 import (
@@ -21,10 +20,6 @@ import (
 	"io"
 )
 
-// We reset the line numbering to test that
-// the formatting works independent of line directives
-//line :19
-
 import (
 	"fmt"
 	"math"
@@ -134,60 +129,3 @@ import (
 
 	"dedup_by_group"
 )
-
-import (
-	/* comment */ io1 "io"
-	"fmt" // for Printf
-	/* comment */ "log"
-	/* comment */ io2 "io"
-)
-
-import (
-	/* comment */ io2 "io" // hello
-	/* comment */ io1 "io"
-	"math" /* right side */
-	"fmt"
-	// end
-)
-
-import (
-	/* comment */ io1 "io" /* before */ // after
-	"fmt"
-	"errors" // for New
-	io2 "io" // another
-	// end
-)
-
-import (
-	/* left */ "fmt" /* right */
-	"errors" // for New
-	/* left */ "math" /* right */
-	"log" // for Fatal
-)
-
-import /* why */ /* comment here? */ (
-	/* comment */ "fmt"
-	"math"
-)
-
-// Reset it again
-//line :100
-
-// Dedup with different import styles
-import (
-	"path"
-	. "path"
-	_ "path"
-	"path"
-	pathpkg "path"
-)
-
-/* comment */
-import (
-	"math" // for Abs
-	"fmt"
-	// This is a new run
-	"errors"
-	"fmt"
-	"errors"
-)
diff --git a/src/go/ast/import.go b/src/go/ast/import.go
index 7102884c85..be23c7fc43 100644
--- a/src/go/ast/import.go
+++ b/src/go/ast/import.go
@@ -30,7 +30,7 @@ func SortImports(fset *token.FileSet, f *File) {
 		i := 0
 		specs := d.Specs[:0]
 		for j, s := range d.Specs {
-			if j > i && lineAt(fset, s.Pos()) > 1+lineAt(fset, d.Specs[j-1].End()) {
+			if j > i && fset.Position(s.Pos()).Line > 1+fset.Position(d.Specs[j-1].End()).Line {
 				// j begins a new run. End this one.
 				specs = append(specs, sortSpecs(fset, f, d.Specs[i:j])...)
 				i = j
@@ -42,8 +42,8 @@ func SortImports(fset *token.FileSet, f *File) {
 		// Deduping can leave a blank line before the rparen; clean that up.
 		if len(d.Specs) > 0 {
 			lastSpec := d.Specs[len(d.Specs)-1]
-			lastLine := lineAt(fset, lastSpec.Pos())
-			rParenLine := lineAt(fset, d.Rparen)
+			lastLine := fset.Position(lastSpec.Pos()).Line
+			rParenLine := fset.Position(d.Rparen).Line
 			for rParenLine > lastLine+1 {
 				rParenLine--
 				fset.File(d.Rparen).MergeLine(rParenLine)
@@ -52,10 +52,6 @@ func SortImports(fset *token.FileSet, f *File) {
 	}
 }
 
-func lineAt(fset *token.FileSet, pos token.Pos) int {
-	return fset.PositionFor(pos, false).Line
-}
-
 func importPath(s Spec) string {
 	t, err := strconv.Unquote(s.(*ImportSpec).Path.Value)
 	if err == nil {
@@ -93,11 +89,6 @@ type posSpan struct {
 	End   token.Pos
 }
 
-type cgPos struct {
-	left bool // true if comment is to the left of the spec, false otherwise.
-	cg   *CommentGroup
-}
-
 func sortSpecs(fset *token.FileSet, f *File, specs []Spec) []Spec {
 	// Can't short-circuit here even if specs are already sorted,
 	// since they might yet need deduplication.
@@ -113,57 +104,39 @@ func sortSpecs(fset *token.FileSet, f *File, specs []Spec) []Spec {
 	}
 
 	// Identify comments in this range.
-	begSpecs := pos[0].Start
-	endSpecs := pos[len(pos)-1].End
-	beg := fset.File(begSpecs).LineStart(lineAt(fset, begSpecs))
-	end := fset.File(endSpecs).LineStart(lineAt(fset, endSpecs) + 1) // beginning of next line
-	first := len(f.Comments)
-	last := -1
+	// Any comment from pos[0].Start to the final line counts.
+	lastLine := fset.Position(pos[len(pos)-1].End).Line
+	cstart := len(f.Comments)
+	cend := len(f.Comments)
 	for i, g := range f.Comments {
-		if g.End() >= end {
-			break
+		if g.Pos() < pos[0].Start {
+			continue
 		}
-		// g.End() < end
-		if beg <= g.Pos() {
-			// comment is within the range [beg, end[ of import declarations
-			if i < first {
-				first = i
-			}
-			if i > last {
-				last = i
-			}
+		if i < cstart {
+			cstart = i
+		}
+		if fset.Position(g.End()).Line > lastLine {
+			cend = i
+			break
 		}
 	}
+	comments := f.Comments[cstart:cend]
 
-	var comments []*CommentGroup
-	if last >= 0 {
-		comments = f.Comments[first : last+1]
-	}
-
-	// Assign each comment to the import spec on the same line.
-	importComments := map[*ImportSpec][]cgPos{}
+	// Assign each comment to the import spec preceding it.
+	importComments := map[*ImportSpec][]*CommentGroup{}
 	specIndex := 0
 	for _, g := range comments {
 		for specIndex+1 < len(specs) && pos[specIndex+1].Start <= g.Pos() {
 			specIndex++
 		}
-		var left bool
-		// A block comment can appear before the first import spec.
-		if specIndex == 0 && pos[specIndex].Start > g.Pos() {
-			left = true
-		} else if specIndex+1 < len(specs) && // Or it can appear on the left of an import spec.
-			lineAt(fset, pos[specIndex].Start)+1 == lineAt(fset, g.Pos()) {
-			specIndex++
-			left = true
-		}
 		s := specs[specIndex].(*ImportSpec)
-		importComments[s] = append(importComments[s], cgPos{left: left, cg: g})
+		importComments[s] = append(importComments[s], g)
 	}
 
 	// Sort the import specs by import path.
 	// Remove duplicates, when possible without data loss.
 	// Reassign the import paths to have the same position sequence.
-	// Reassign each comment to the spec on the same line.
+	// Reassign each comment to abut the end of its spec.
 	// Sort the comments by new position.
 	sort.Slice(specs, func(i, j int) bool {
 		ipath := importPath(specs[i])
@@ -187,7 +160,7 @@ func sortSpecs(fset *token.FileSet, f *File, specs []Spec) []Spec {
 			deduped = append(deduped, s)
 		} else {
 			p := s.Pos()
-			fset.File(p).MergeLine(lineAt(fset, p))
+			fset.File(p).MergeLine(fset.Position(p).Line)
 		}
 	}
 	specs = deduped
@@ -201,16 +174,8 @@ func sortSpecs(fset *token.FileSet, f *File, specs []Spec) []Spec {
 		s.Path.ValuePos = pos[i].Start
 		s.EndPos = pos[i].End
 		for _, g := range importComments[s] {
-			for _, c := range g.cg.List {
-				if g.left {
-					c.Slash = pos[i].Start - 1
-				} else {
-					// An import spec can have both block comment and a line comment
-					// to its right. In that case, both of them will have the same pos.
-					// But while formatting the AST, the line comment gets moved to
-					// after the block comment.
-					c.Slash = pos[i].End
-				}
+			for _, c := range g.List {
+				c.Slash = pos[i].End
 			}
 		}
 	}