[go] go/ast: document CommentGroup types
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Mateusz Poliwczak (Gerrit)
Sep 16, 2025, 2:53:18 AMSep 16
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Mateusz Poliwczak has uploaded the change for review![]( "Open in Gerrit")
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go/ast: document CommentGroup types
Change-Id: I6a6a696484cfbc438468f048f6c7088f4257cdbc
Change diff
diff --git a/src/go/ast/ast.go b/src/go/ast/ast.go
index a3dc0c3..543cb83 100644
--- a/src/go/ast/ast.go
+++ b/src/go/ast/ast.go
@@ -75,6 +75,14 @@
// A CommentGroup represents a sequence of comments
// with no other tokens and no empty lines between.
+//
+// There are two separate types of comment groups, both represented by a CommentGroup:
+// - Line comment group: comments where every comment starts on the same line.
+// Such group is recognized by [go/parser] when, before a COMMENT token,
+// another (non-COMMENT) token appears on the same line before.
+// - Block comment group: a block of comments, comments might start at different lines, but
+// such comments cannot be separated by an empty line.
+// Such group is recognized by [go/parser] when a COMMENT token is the first token on a line.
type CommentGroup struct {
List []*Comment // len(List) > 0
}
Change information
Files:
- M src/go/ast/ast.go
Change size: XS
Delta: 1 file changed, 8 insertions(+), 0 deletions(-)
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Mateusz Poliwczak (Gerrit)
Sep 16, 2025, 10:18:54 AMSep 16
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Alan Donovan (Gerrit)
Sep 16, 2025, 11:07:44 AMSep 16
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Alan Donovan added 2 comments![]( "Open in Gerrit")
File src/go/ast/ast.go
Line 79, Patchset 3 (Latest):
// There are two separate types of comment groups, both represented by a CommentGroup:Alan Donovan . unresolved
Tighter:
The parser creates two kinds of CommentGroup.
A line comment group is a sequence of comments all on the same line, following a token on that line.
A block comment group is a sequence of comments, starting on a line without tokens.
In other words, the parser promises both "maximal munch", and not to conjoin a line comment group with a block comment in cases such as this:
```
foo // line
// block
```
We should probably await gri's comments before strengthening the parser's postcondition.
Line 80, Patchset 3 (Latest):
// - Line comment group: Recognized by [go/parser] when a comment is not the first
// token on the line. Such group ends when a non-comment token, an empty lineAlan Donovan . resolved
Comments are not tokens, BTW.
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Robert Griesemer (Gerrit)
12:51 PM (10 hours ago) 12:51 PM
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Robert Griesemer added 2 comments![]( "Open in Gerrit")
Patchset-level comments
File-level comment, Patchset 5 (Latest):
Robert Griesemer . resolved
I'll have to re-read the comment group logic to verify correctness of this comment. It's been a while...
adonovan: how are we strengthening the parser's postcondition?
File src/go/ast/ast.go
Line 81, Patchset 5 (Latest):
// token on the line. Such group ends when a non-comment token, an empty lineRobert Griesemer . unresolved
Since comments are not tokens, maybe:
... when a token (not a comment) ...
Also below.
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Mateusz Poliwczak (Gerrit)
12:58 PM (10 hours ago) 12:58 PM
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Mateusz Poliwczak uploaded new patchset![]( "Open in Gerrit")
Mateusz Poliwczak uploaded patch set #6 to this change.
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Mateusz Poliwczak (Gerrit)
12:59 PM (9 hours ago) 12:59 PM
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Mateusz Poliwczak voted and added 3 comments![]( "Open in Gerrit")
Votes added by Mateusz Poliwczak
| Commit-Queue | +1 |
Robert Griesemer . resolved
I'll have to re-read the comment group logic to verify correctness of this comment. It's been a while...
adonovan: how are we strengthening the parser's postcondition?
Mateusz Poliwczak
I'll have to re-read the comment group logic to verify correctness of this comment. It's been a while...
FYI skimming CL 703815 might help with that (not sure we want that change though).
File src/go/ast/ast.go
Line 79, Patchset 3:
// There are two separate types of comment groups, both represented by a CommentGroup:Alan Donovan . resolved
Tighter:
The parser creates two kinds of CommentGroup.
A line comment group is a sequence of comments all on the same line, following a token on that line.
A block comment group is a sequence of comments, starting on a line without tokens.In other words, the parser promises both "maximal munch", and not to conjoin a line comment group with a block comment in cases such as this:
```
foo // line
// block
```We should probably await gri's comments before strengthening the parser's postcondition.
Mateusz Poliwczak
Updated the comment.
Line 81, Patchset 5:
// token on the line. Such group ends when a non-comment token, an empty lineRobert Griesemer . resolved
Since comments are not tokens, maybe:
... when a token (not a comment) ...Also below.
Mateusz Poliwczak
I think i prefer the tighter version of this comment (as written by Alan). WDYT?
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Mateusz Poliwczak (Gerrit)
1:14 PM (9 hours ago) 1:14 PM
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Mateusz Poliwczak voted Commit-Queue+1![]( "Open in Gerrit")
| Commit-Queue | +1 |
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