go/parser: report //go:build-derived Go version in ast.File.GoVersion

For #57001, compilers and others tools will need to understand that
a different Go version can be used in different files in a program,
according to the //go:build lines in those files.

Update go/parser to populate the new ast.File.GoVersion field.

This requires running the go/scanner in ParseComments mode
always and then implementing discarding of comments in the
parser instead of the scanner. The same work is done either way,
since the scanner was already preparing the comment result
and then looping. The loop has just moved into go/parser.

Also make the same changes to cmd/compile/internal/syntax,
both because they're necessary and to keep in sync with go/parser.

For #59033.

Change-Id: I7b867f5f9aaaccdca94af146b061d16d9a3fd07f
Reviewed-on: https://go-review.googlesource.com/c/go/+/476277
Auto-Submit: Russ Cox <rsc@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>

diff --git a/src/cmd/compile/internal/syntax/nodes.go b/src/cmd/compile/internal/syntax/nodes.go
index e943a9a9e672c97e7dc947bceb3b5925aa99e395..6580f053c778c7f42024b67ab1fc3d05edd32af8 100644 (file)
--- a/src/cmd/compile/internal/syntax/nodes.go
+++ b/src/cmd/compile/internal/syntax/nodes.go
@@ -34,10 +34,11 @@ func (*node) aNode()     {}
 
 // package PkgName; DeclList[0], DeclList[1], ...
 type File struct {
-       Pragma   Pragma
-       PkgName  *Name
-       DeclList []Decl
-       EOF      Pos
+       Pragma    Pragma
+       PkgName   *Name
+       DeclList  []Decl
+       EOF       Pos
+       GoVersion string
        node
 }
 

diff --git a/src/cmd/compile/internal/syntax/parser.go b/src/cmd/compile/internal/syntax/parser.go
index ee9761e4a6e50dc525c093ea61da897f9ea0023b..c8b8ab06018b8eea07c4c39eb689cc3164241bc8 100644 (file)
--- a/src/cmd/compile/internal/syntax/parser.go
+++ b/src/cmd/compile/internal/syntax/parser.go
@@ -6,6 +6,7 @@ package syntax
 
 import (
        "fmt"
+       "go/build/constraint"
        "io"
        "strconv"
        "strings"
@@ -21,17 +22,20 @@ type parser struct {
        pragh PragmaHandler
        scanner
 
-       base   *PosBase // current position base
-       first  error    // first error encountered
-       errcnt int      // number of errors encountered
-       pragma Pragma   // pragmas
+       base      *PosBase // current position base
+       first     error    // first error encountered
+       errcnt    int      // number of errors encountered
+       pragma    Pragma   // pragmas
+       goVersion string   // Go version from //go:build line
 
+       top    bool   // in top of file (before package clause)
        fnest  int    // function nesting level (for error handling)
        xnest  int    // expression nesting level (for complit ambiguity resolution)
        indent []byte // tracing support
 }
 
 func (p *parser) init(file *PosBase, r io.Reader, errh ErrorHandler, pragh PragmaHandler, mode Mode) {
+       p.top = true
        p.file = file
        p.errh = errh
        p.mode = mode
@@ -70,8 +74,15 @@ func (p *parser) init(file *PosBase, r io.Reader, errh ErrorHandler, pragh Pragm
                        }
 
                        // go: directive (but be conservative and test)
-                       if pragh != nil && strings.HasPrefix(text, "go:") {
-                               p.pragma = pragh(p.posAt(line, col+2), p.scanner.blank, text, p.pragma) // +2 to skip over // or /*
+                       if strings.HasPrefix(text, "go:") {
+                               if p.top && strings.HasPrefix(msg, "//go:build") {
+                                       if x, err := constraint.Parse(msg); err == nil {
+                                               p.goVersion = constraint.GoVersion(x)
+                                       }
+                               }
+                               if pragh != nil {
+                                       p.pragma = pragh(p.posAt(line, col+2), p.scanner.blank, text, p.pragma) // +2 to skip over // or /*
+                               }
                        }
                },
                directives,
@@ -388,6 +399,8 @@ func (p *parser) fileOrNil() *File {
        f.pos = p.pos()
 
        // PackageClause
+       f.GoVersion = p.goVersion
+       p.top = false
        if !p.got(_Package) {
                p.syntaxError("package statement must be first")
                return nil

diff --git a/src/go/build/deps_test.go b/src/go/build/deps_test.go
index a287eeda67eb878668edd14a119fc9e5b54bc594..306d0390343f4a8a49e1cbd3092e321c33ba8492 100644 (file)
--- a/src/go/build/deps_test.go
+++ b/src/go/build/deps_test.go
@@ -263,13 +263,15 @@ var depsRules = `
        < go/token
        < go/scanner
        < go/ast
-       < go/internal/typeparams
-       < go/parser;
+       < go/internal/typeparams;
 
        FMT
        < go/build/constraint, go/doc/comment;
 
-       go/build/constraint, go/doc/comment, go/parser, text/tabwriter
+       go/internal/typeparams, go/build/constraint
+       < go/parser;
+
+       go/doc/comment, go/parser, text/tabwriter
        < go/printer
        < go/format;
 

diff --git a/src/go/parser/parser.go b/src/go/parser/parser.go
index dec02452613fa8866aab3513dfb6f22d43eee82b..e1d941eff31d3bb50fd971bb33f0e26bee5cbd41 100644 (file)
--- a/src/go/parser/parser.go
+++ b/src/go/parser/parser.go
@@ -18,9 +18,11 @@ package parser
 import (
        "fmt"
        "go/ast"
+       "go/build/constraint"
        "go/internal/typeparams"
        "go/scanner"
        "go/token"
+       "strings"
 )
 
 // The parser structure holds the parser's internal state.
@@ -38,6 +40,8 @@ type parser struct {
        comments    []*ast.CommentGroup
        leadComment *ast.CommentGroup // last lead comment
        lineComment *ast.CommentGroup // last line comment
+       top         bool              // in top of file (before package clause)
+       goVersion   string            // minimum Go version found in //go:build comment
 
        // Next token
        pos token.Pos   // token position
@@ -64,13 +68,10 @@ type parser struct {
 
 func (p *parser) init(fset *token.FileSet, filename string, src []byte, mode Mode) {
        p.file = fset.AddFile(filename, -1, len(src))
-       var m scanner.Mode
-       if mode&ParseComments != 0 {
-               m = scanner.ScanComments
-       }
        eh := func(pos token.Position, msg string) { p.errors.Add(pos, msg) }
-       p.scanner.Init(p.file, src, eh, m)
+       p.scanner.Init(p.file, src, eh, scanner.ScanComments)
 
+       p.top = true
        p.mode = mode
        p.trace = mode&Trace != 0 // for convenience (p.trace is used frequently)
        p.next()
@@ -142,7 +143,23 @@ func (p *parser) next0() {
                }
        }
 
-       p.pos, p.tok, p.lit = p.scanner.Scan()
+       for {
+               p.pos, p.tok, p.lit = p.scanner.Scan()
+               if p.tok == token.COMMENT {
+                       if p.top && strings.HasPrefix(p.lit, "//go:build") {
+                               if x, err := constraint.Parse(p.lit); err == nil {
+                                       p.goVersion = constraint.GoVersion(x)
+                               }
+                       }
+                       if p.mode&ParseComments == 0 {
+                               continue
+                       }
+               } else {
+                       // Found a non-comment; top of file is over.
+                       p.top = false
+               }
+               break
+       }
 }
 
 // Consume a comment and return it and the line on which it ends.
@@ -2851,6 +2868,7 @@ func (p *parser) parseFile() *ast.File {
                FileEnd:   token.Pos(p.file.Base() + p.file.Size()),
                Imports:   p.imports,
                Comments:  p.comments,
+               GoVersion: p.goVersion,
        }
        var declErr func(token.Pos, string)
        if p.mode&DeclarationErrors != 0 {

diff --git a/src/go/parser/parser_test.go b/src/go/parser/parser_test.go
index 22b11a0cc453548e37aeee0bd90ec5f2dcfd1f4b..65c8520b491f5dbc3dc66db2296d86c8b6c5c925 100644 (file)
--- a/src/go/parser/parser_test.go
+++ b/src/go/parser/parser_test.go
@@ -780,3 +780,23 @@ func TestIssue59180(t *testing.T) {
                }
        }
 }
+
+func TestGoVersion(t *testing.T) {
+       fset := token.NewFileSet()
+       pkgs, err := ParseDir(fset, "./testdata/goversion", nil, 0)
+       if err != nil {
+               t.Fatal(err)
+       }
+
+       for _, p := range pkgs {
+               want := strings.ReplaceAll(p.Name, "_", ".")
+               if want == "none" {
+                       want = ""
+               }
+               for _, f := range p.Files {
+                       if f.GoVersion != want {
+                               t.Errorf("%s: GoVersion = %q, want %q", fset.Position(f.Pos()), f.GoVersion, want)
+                       }
+               }
+       }
+}

diff --git a/src/go/parser/testdata/goversion/t01.go b/src/go/parser/testdata/goversion/t01.go
new file mode 100644 (file)
index 0000000..5cfa0cc
--- /dev/null
+++ b/src/go/parser/testdata/goversion/t01.go
@@ -0,0 +1,3 @@
+//go:build windows
+
+package none

diff --git a/src/go/parser/testdata/goversion/t02.go b/src/go/parser/testdata/goversion/t02.go
new file mode 100644 (file)
index 0000000..d91f995
--- /dev/null
+++ b/src/go/parser/testdata/goversion/t02.go
@@ -0,0 +1,3 @@
+//go:build linux && go1.2
+
+package go1_2

diff --git a/src/go/parser/testdata/goversion/t03.go b/src/go/parser/testdata/goversion/t03.go
new file mode 100644 (file)
index 0000000..97fc9ae
--- /dev/null
+++ b/src/go/parser/testdata/goversion/t03.go
@@ -0,0 +1,3 @@
+//go:build linux && go1.2 || windows
+
+package none

diff --git a/src/go/parser/testdata/goversion/t04.go b/src/go/parser/testdata/goversion/t04.go
new file mode 100644 (file)
index 0000000..e81f9c0
--- /dev/null
+++ b/src/go/parser/testdata/goversion/t04.go
@@ -0,0 +1,5 @@
+// copyright notice
+
+//go:build (linux && go1.2) || (windows && go1.1)
+
+package go1_1

diff --git a/src/go/parser/testdata/goversion/t05.go b/src/go/parser/testdata/goversion/t05.go
new file mode 100644 (file)
index 0000000..42c6b33
--- /dev/null
+++ b/src/go/parser/testdata/goversion/t05.go
@@ -0,0 +1,3 @@
+//go:build linux && go1.2 && go1.4
+
+package go1_4

diff --git a/src/go/parser/testdata/goversion/t06.go b/src/go/parser/testdata/goversion/t06.go
new file mode 100644 (file)
index 0000000..22944de
--- /dev/null
+++ b/src/go/parser/testdata/goversion/t06.go
@@ -0,0 +1,3 @@
+//go:build go1
+
+package go1