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cmd/compile: incorrect positions recorded in export data #19391

@griesemer

Description

@griesemer

Compiling the following file:

package p

//line c.go:10
const C = 0      // file line = 4

//line t.go:20
type T int       // file line = 7

//line v.go:30
var V T          // file line = 10

//line f.go:40
func F() {}      // file line = 13

records the following positions in the export data:

C c.go 4
T /Users/gri/tmp/x.go 14
V v.go 10
F f.go 13

Except for V they are all surprising, one way or the other. The output from the syntax package is as follows in this case:

$ go test -v -run Dump -src=$HOME/tmp/x.go
=== RUN   TestDump
     1  *syntax.File {
     2  .  PkgName: p @ /Users/gri/tmp/x.go:1
     3  .  DeclList: []syntax.Decl (4 entries) {
     4  .  .  0: *syntax.ConstDecl {
     5  .  .  .  NameList: []*syntax.Name (1 entries) {
     6  .  .  .  .  0: C @ c.go:10[/Users/gri/tmp/x.go:3]
     7  .  .  .  }
     8  .  .  .  Type: nil
     9  .  .  .  Values: *syntax.BasicLit {
    10  .  .  .  .  Value: "0"
    11  .  .  .  .  Kind: 0
    12  .  .  .  }
    13  .  .  .  Group: nil
    14  .  .  }
    15  .  .  1: *syntax.TypeDecl {
    16  .  .  .  Name: T @ t.go:20[/Users/gri/tmp/x.go:6]
    17  .  .  .  Alias: false
    18  .  .  .  Type: int @ t.go:20[/Users/gri/tmp/x.go:6]
    19  .  .  .  Group: nil
    20  .  .  .  Pragma: 0
    21  .  .  }
    22  .  .  2: *syntax.VarDecl {
    23  .  .  .  NameList: []*syntax.Name (1 entries) {
    24  .  .  .  .  0: V @ v.go:30[/Users/gri/tmp/x.go:9]
    25  .  .  .  }
    26  .  .  .  Type: T @ v.go:30[/Users/gri/tmp/x.go:9]
    27  .  .  .  Values: nil
    28  .  .  .  Group: nil
    29  .  .  }
    30  .  .  3: *syntax.FuncDecl {
    31  .  .  .  Attr: map[]
    32  .  .  .  Recv: nil
    33  .  .  .  Name: F @ f.go:40[/Users/gri/tmp/x.go:12]
    34  .  .  .  Type: *syntax.FuncType {
    35  .  .  .  .  ParamList: nil
    36  .  .  .  .  ResultList: nil
    37  .  .  .  }
    38  .  .  .  Body: []syntax.Stmt (1 entries) {
    39  .  .  .  .  0: *syntax.EmptyStmt {
    40  .  .  .  .  }
    41  .  .  .  }
    42  .  .  .  Pragma: 0
    43  .  .  .  EndLine: 13
    44  .  .  }
    45  .  }
    46  .  Lines: 14
    47  }
--- PASS: TestDump (0.18s)

which shows consistent positions with the Name nodes (albeit they are off by 1).

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