mirror of
https://github.com/fish-shell/fish-shell
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971d257e67
The translation is fairly direct though it adds some duplication, for example
there are multiple "match" statements that mimic function overloading.
Rust has no overloading, and we cannot have generic methods in the Node trait
(due to a Rust limitation, the error is like "cannot be made into an object")
so we include the type name in method names.
Give clients like "indent_visitor_t" a Rust companion ("IndentVisitor")
that takes care of the AST traversal while the AST consumption remains
in C++ for now. In future, "IndentVisitor" should absorb the entirety of
"indent_visitor_t". This pattern requires that "fish_indent" be exposed
includable header to the CXX bridge.
Alternatively, we could define FFI wrappers for recursive AST traversal.
Rust requires we separate the AST visitors for "mut" and "const"
scenarios. Take this opportunity to concretize both visitors:
The only client that requires mutable access is the populator. To match the
structure of the C++ populator which makes heavy use of function overloading,
we need to add a bunch of functions to the trait. Since there is no other
mutable visit, this seems acceptable.
The "const" visitors never use "will_visit_fields_of()" or
"did_visit_fields_of()", so remove them (though this is debatable).
Like in the C++ implementation, the AST nodes themselves are largely defined
via macros. Union fields like "Statement" and "ArgumentOrRedirection"
do currently not use macros but may in future.
This commit also introduces a precedent for a type that is defined in one
CXX bridge and used in another one - "ParseErrorList". To make this work
we need to manually define "ExternType".
There is one annoyance with CXX: functions that take explicit lifetime
parameters require to be marked as unsafe. This makes little sense
because functions that return `&Foo` with implicit lifetime can be
misused the same way on the C++ side.
One notable change is that we cannot directly port "find_block_open_keyword()"
(which is used to compute an error) because it relies on the stack of visited
nodes. We cannot modify a stack of node references while we do the "mut"
walk. Happily, an idiomatic solution is easy: we can tell the AST visitor
to backtrack to the parent node and create the error there.
Since "node_t::accept_base" is no longer a template we don't need the
"node_visitation_t" trampoline anymore.
The added copying at the FFI boundary makes things slower (memcpy dominates
the profile) but it's not unusable, which is good news:
$ hyperfine ./fish.{old,new}" -c 'source ../share/completions/git.fish'"
Benchmark 1: ./fish.old -c 'source ../share/completions/git.fish'
Time (mean ± σ): 195.5 ms ± 2.9 ms [User: 190.1 ms, System: 4.4 ms]
Range (min … max): 193.2 ms … 205.1 ms 15 runs
Benchmark 2: ./fish.new -c 'source ../share/completions/git.fish'
Time (mean ± σ): 677.5 ms ± 62.0 ms [User: 665.4 ms, System: 10.0 ms]
Range (min … max): 611.7 ms … 805.5 ms 10 runs
Summary
'./fish.old -c 'source ../share/completions/git.fish'' ran
3.47 ± 0.32 times faster than './fish.new -c 'source ../share/completions/git.fish''
Leftovers:
- Enum variants are still snakecase; I didn't get around to changing this yet.
- "ast_type_to_string()" still returns a snakecase name. This could be
changed since it's not user visible.
93 lines
2.5 KiB
C++
93 lines
2.5 KiB
C++
// Programmatic representation of fish grammar.
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#ifndef FISH_AST_H
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#define FISH_AST_H
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#include <cstddef>
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#include <cstdint>
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#include <initializer_list>
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#include <iterator>
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#include <memory>
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#include <type_traits>
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#include <utility>
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#include <vector>
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#include "common.h"
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#include "cxx.h"
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#include "maybe.h"
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#include "parse_constants.h"
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#if INCLUDE_RUST_HEADERS
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#include "ast.rs.h"
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namespace ast {
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using ast_t = Ast;
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using category_t = Category;
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using type_t = Type;
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using andor_job_list_t = AndorJobList;
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using andor_job_t = AndorJob;
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using argument_list_t = ArgumentList;
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using argument_or_redirection_list_t = ArgumentOrRedirectionList;
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using argument_or_redirection_t = ArgumentOrRedirection;
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using argument_t = Argument;
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using begin_header_t = BeginHeader;
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using block_statement_t = BlockStatement;
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using case_item_t = CaseItem;
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using decorated_statement_t = DecoratedStatement;
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using elseif_clause_list_t = ElseifClauseList;
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using for_header_t = ForHeader;
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using freestanding_argument_list_t = FreestandingArgumentList;
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using function_header_t = FunctionHeader;
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using if_clause_t = IfClause;
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using if_statement_t = IfStatement;
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using job_conjunction_continuation_t = JobConjunctionContinuation;
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using job_conjunction_t = JobConjunction;
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using job_continuation_t = JobContinuation;
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using job_list_t = JobList;
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using job_pipeline_t = JobPipeline;
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using maybe_newlines_t = MaybeNewlines;
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using not_statement_t = NotStatement;
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using redirection_t = Redirection;
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using semi_nl_t = SemiNl;
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using statement_t = Statement;
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using string_t = String_;
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using switch_statement_t = SwitchStatement;
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using variable_assignment_list_t = VariableAssignmentList;
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using variable_assignment_t = VariableAssignment;
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using while_header_t = WhileHeader;
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} // namespace ast
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#else
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struct Ast;
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struct NodeFfi;
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namespace ast {
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using ast_t = Ast;
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struct argument_t;
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struct block_statement_t;
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struct statement_t;
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struct string_t;
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struct maybe_newlines_t;
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struct redirection_t;
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struct variable_assignment_t;
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struct semi_nl_t;
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struct decorated_statement_t;
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struct keyword_base_t;
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} // namespace ast
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#endif
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namespace ast {
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using node_t = ::NodeFfi;
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}
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rust::Box<Ast> ast_parse(const wcstring &src, parse_tree_flags_t flags = parse_flag_none,
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parse_error_list_t *out_errors = nullptr);
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rust::Box<Ast> ast_parse_argument_list(const wcstring &src,
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parse_tree_flags_t flags = parse_flag_none,
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parse_error_list_t *out_errors = nullptr);
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#endif // FISH_AST_H
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