syntax-profile.md

Safe-core syntax acceptance profile

P1-02 is 🚧 In progress. Manifest version 2 of safe-core-syntax fixes a 36-case, 16-category acceptance denominator for the current bounded parser. This increment does not close the full safe-core grammar gate. The language baseline is Rust 1.98.0, Edition 2024; lexical representation follows the lexical contract.

Included grammar

Category ID	Current syntax
modules	Compilation units and nested inline mod name { ... } items, private or pub.
imports	Simple use paths with crate/self/super, raw identifiers and an optional named as alias; whitespace and comments separate tokens.
functions	Named functions with typed pattern parameters, optional return type and a required block body.
structs	Named-field, tuple-field and unit structs; pub fields are retained. Unit and empty braced forms remain distinct in AST and HIR.
enums	Unit and tuple-payload variants, including empty tuple payloads and trailing commas.
aliases-constants	Type aliases and typed initialized constants.
statements	let, optional type/initializer, return, expression statements and block tail expressions. A final return may omit its semicolon.
expressions	Paths, calls, indexing, parentheses/tuples, array lists/repeats, blocks, if/else if/else, and the built-in println!(...) form.
operator-binding	Rust arithmetic, bitwise, comparison, logical, assignment and compound-assignment precedence. Comparisons are non-associative; assignments associate right. Unary minus, not, dereference and shared/mutable borrow are included.
patterns	Identifier/mutable bindings, wildcard, literals including negative numbers, parentheses/tuples, paths and tuple-constructor patterns.
types	Path/type arguments, shared/mutable references with optional lifetime spelling, parentheses/tuples, arrays, slices, unit and never.
generics	Type parameter lists and path bounds. Empty lists/bounds and a trailing bound + are legal Rust syntax. Nested generic closers split >>, >= and >>= without changing lexical tokens.
attributes	Compilation-unit inner preamble attributes and outer item attributes. Paths are parsed as tokens; delimited token arguments and literal = values retain source text.
literals	Every lexer literal family and boolean literals; expression/pattern suffixes are validated.
malformed	Missing expressions/separators, invalid import/attribute forms, repeat-array arity, malformed generic bounds, chained comparisons, unary +, and keyword declaration names.
unsupported	Explicit RSP1003 diagnostics for the excluded forms exercised in the manifest and regression harness.

Parentheses are represented by one-element tuple nodes without a trailing comma; the original span and comma flag distinguish them from one-element tuples. Generic segment spans include their closing delimiter. Splitting joint punctuation retains each consumed character's span and leaves shifts and shift assignments intact in expression contexts. &&T and &&mut value represent two reference/borrow nodes.

Attributes are syntax only: token arguments are not expanded or interpreted as macros. Documentation comments remain lexical trivia. Type correctness, name resolution, pattern refutability and borrow rules are separate passes. A parse-pass fixture can intentionally contain unresolved names or incompatible types; it is not necessarily a compilable Rust program.

Remaining P1-02 work

P1-02 remains 🚧 In progress for broader safe-core syntax and its full AST acceptance denominator: grouped/glob/absolute/underscore imports, restricted visibility, inner module/block attributes and documentation desugaring, lifetime/const generic declarations and arguments, defaults and where, traits/impls, function types, struct expressions and struct-like enum variants, field/method access, casts, richer patterns, match, loops and closures. External module declarations also remain excluded pending workspace loading.

The current parser explicitly rejects representative excluded forms. Other unimplemented combinations may produce RSP1001/RSP1002; this increment does not claim comprehensive RSP1003 coverage or a full AST snapshot denominator. Unsafe/FFI and general macro expansion belong to separate profiles. Executable support remains the narrower primitive profile.

Resource bounds

The manifest fixes 1,000,000 UTF-16 characters, 250,000 tokens, 100,000 AST nodes, 128 diagnostics, 128 syntax nesting levels and 1,000,000 parser operations per case. timeoutMilliseconds is 10,000, shared by lexing and parsing. The public four-argument SafeCoreSyntax.Parse overload forwards cancellation to both passes. Cancellation throws OperationCanceledException; deadline expiry throws TimeoutException; neither produces successful or ordinary parse-fail evidence.

Collection/work exhaustion returns a truncated result with no root and a bounded diagnostic list. Recovery and recursive else if chains obey parser budgets. The runner limits manifests to 256 KiB, 64 cases, 8,192 JSON tokens and a separate harness deadline. It rejects duplicate properties, unknown fields, unsupported baselines, invalid paths, missing categories, undeclared case references and mismatched denominators. Every fixture belongs to at least one of the fixed 16 categories. Timeout/truncation is not a grammar rejection.

Acceptance evidence

dotnet build RustSharp.slnx -c Release
dotnet run --project tests/RustSharp.Tests -c Release --no-build --no-restore
dotnet run --project tools/RustSharp.Conformance -c Release --no-build --no-restore -- --profile safe-core-syntax
pwsh -NoProfile -File eng/Test-SyntaxEvidence.ps1

The report at artifacts/conformance/safe-core-syntax.json uses schema version 2. It records manifest/source hashes, baseline, category map, exact case IDs, parser limits, expected outcomes, item/function minima, diagnostics and source spans. Each parse-fail must match both its diagnostic code and the exact source text under that diagnostic. Untruncated results must reconstruct the source. AST shape regressions separately check precedence, punctuation splitting, references, attributes, unit structs and HIR preservation. Invalid manifest and incorrect expectation mutations test that evidence cannot pass vacuously.

Windows/Linux CI call eng/Test-SyntaxEvidence.ps1, which compares the report against current manifest and fixture hashes, categories, outcomes and diagnostic spans. Local execution does not imply a new remote CI run. Evidence is labeled parser-acceptance, with rustc differential and runtime conformance both false.