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go/parser: add a SkipObjectResolution mode to bypass object resolution

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Parser object resolution is an auxiliary feature in which the parser
attempts to resolve identifiers to their declarations. In functionality,
it significantly overlaps with go/types and in fact cannot be correctly
computed at parse-time without type information (for example, it is
generally not possible to resolve k in the composite lit c{k: v}). Due
to these limitations, it is of limited utility and rarely used.

Now that object resolution is isolated as a post-processing pass, it is
trivial to offer a parser mode that skips it entirely. This CL adds that
mode.

Fixes #45104

Change-Id: I5a2c05437e298964ad2039e1ff98e63d6efbd1af
Reviewed-on: https://go-review.googlesource.com/c/go/+/306149
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Rob Findley 2021-03-29 16:03:51 -04:00 • committed by Robert Findley
parent b91f8a4c0b
commit 02a2ff47ef
2 changed files with 17 additions and 10 deletions
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23
src/go/parser/interface.go
View file

@ -49,13 +49,14 @@ func readSource(filename string, src interface{}) ([]byte, error) {
type Mode uint
const (
PackageClauseOnly Mode = 1 << iota // stop parsing after package clause
ImportsOnly // stop parsing after import declarations
ParseComments // parse comments and add them to AST
Trace // print a trace of parsed productions
DeclarationErrors // report declaration errors
SpuriousErrors // same as AllErrors, for backward-compatibility
AllErrors = SpuriousErrors // report all errors (not just the first 10 on different lines)
PackageClauseOnly Mode = 1 << iota // stop parsing after package clause
ImportsOnly // stop parsing after import declarations
ParseComments // parse comments and add them to AST
Trace // print a trace of parsed productions
DeclarationErrors // report declaration errors
SpuriousErrors // same as AllErrors, for backward-compatibility
SkipObjectResolution // don't resolve identifiers to objects - see ParseFile
AllErrors = SpuriousErrors // report all errors (not just the first 10 on different lines)
)
// ParseFile parses the source code of a single Go source file and returns
@ -68,8 +69,12 @@ const (
// If src == nil, ParseFile parses the file specified by filename.
//
// The mode parameter controls the amount of source text parsed and other
// optional parser functionality. Position information is recorded in the
// file set fset, which must not be nil.
// optional parser functionality. If the SkipObjectResolution mode bit is set,
// the object resolution phase of parsing will be skipped, causing File.Scope,
// File.Unresolved, and all Ident.Obj fields to be nil.
//
// Position information is recorded in the file set fset, which must not be
// nil.
//
// If the source couldn't be read, the returned AST is nil and the error
// indicates the specific failure. If the source was read but syntax

4
src/go/parser/parser.go
View file

@ -2636,7 +2636,9 @@ func (p *parser) parseFile() *ast.File {
if p.mode&DeclarationErrors != 0 {
declErr = p.error
}
resolveFile(f, p.file, declErr)
if p.mode&SkipObjectResolution == 0 {
resolveFile(f, p.file, declErr)
}
return f
}