v2.20.0

What's Changed

Highlights

• Tuple element access via t.0 syntax. Tuple elements can now be accessed positionally with dot notation (t.0, t.1, …), including nested access, assignments, ref arguments, and access through snapshots. #10111 #10153
• #[panic_with] is deprecated. Using the attribute without opting in via #[feature("deprecated-panic-with")] now emits a warning; prefer plain calculations (now supported in const context) or explicit .expect(...) calls. As part of this, the generated wrapper functions were removed from the corelib — see the breaking change under Corelib below. #10096
• Faster incremental recompilation. Syntax node ids are now kept stable across reparses and plugin-generated files are cached, restoring salsa early cutoff so a structure-preserving edit no longer re-walks the rest of the file — noticeably speeding up the language server. #10105 #10164

Features

• Support tuple element access via t.0 syntax. #10111 #10153
• Deprecated the #[panic_with] attribute; opt in with #[feature("deprecated-panic-with")] to silence the warning. #10096
• Warn (E2201) when an extern type or function is declared outside the core library; suppress with #[allow(extern_outside_corelib)]. #10147
• Support struct-update (..base) syntax in const expressions. #10136
• Evaluate !, &, |, and ^ on bool operands in const contexts. #10212
• Populate MacroPluginMetadata::allowed_features so macro plugins can honor #[feature(...)]. #10094

Bug Fixes

• Reject types that are (or transitively contain) a phantom type when used as values, in signatures, or as array elements, including nested and cyclic cases (E2019), instead of silently compiling or hitting an ICE. #10120 #10169 #10171 #10175
• Disable Felt252Dict construction for illegal value types. #10118
• Emit a diagnostic (E2075) for glob (*) use items in statement position instead of silently accepting them. #10148
• Reject #[default] on a struct member instead of silently ignoring it. #10228
• Fixed derive(Hash)/derive(Serde) codegen for enums, and sanitized the generated hash/serde implementations. #10080 #10117
• Emit derive member bounds for associated-type-path members. #10176
• Validate the quotient in const DivRem to avoid a signed MIN/-1 ICE. #10140
• Substitute the result of generic const function calls with the concrete call-site types. #10143
• Include captured_types in the closure occurs-check. #10086
• Don't ICE on a Deref impl with the wrong number of associated types. #10183
• Don't ICE when an impl provides an associated item of the wrong kind. #10206
• Report every invalid associated-item constraint, not just the first. #10207
• Don't ICE on a wrong generic-argument count reached through a local use alias. #10211
• Report a glob name collision of non-visible items as not-visible rather than ambiguous. #10209
• Apply feature/visibility gating to glob re-exports of generic items. #10217
• Enforce the fixed-size-array size cap on the type form. #10218
• Attribute format!/print! bracket errors to the right macro. #10222
• writeln!(f) with no format string now writes a newline. #10182
• Apply full type-based diagnostics to all parts of a function signature. #10170
• Removed an extra diagnostic emitted for type mismatches on missing. #10121
• Fixed punctuation/newline of bare crate-root diagnostics. #10087
• Skipped-token diagnostic now spans the token, not its leading comment. #10088
• Validate the literal in a negative const generic argument, and anchor literal-validation diagnostics at the token text. #10091 #10103
• Treat //// as a regular comment, not a doc comment. #10107
• Make macro a valid recovery terminal and tree token. #10149
• Stop block recovery at a following control-flow statement. #10227
• Dedup panic_destruct calls for a variable at a shared panic location. #10205
• Normalize storage_base_address_from_felt252 const folding. #10210
• Prune usage after change promotion in loop usage finalization. #10201
• Name macro-call modules by macro name and offset instead of raw call text. #10197
• Close the ] in the FixedSizeArray type short name. #10172
• Fixed a from_trace panic by profiling coupon_call like function_call in the runner. #10081
• Make inline doc links with markup point to their URL. #10151
• Collect executables from modules generated by macro calls. by @integraledelebesgue in #10184

Starknet

• Fully-qualify prelude types in contract codegen. #10137
• Clearer error for a non-ref self constructor. #10223
• Calling meta_tx_v0 no longer crashes cairo test. #10219
• Fixed test-deployment hygiene issues in the Starknet plugin. #10173
• Reject crafted out-of-range type ids instead of panicking when building a Starknet class. #10224
• Validate entry-point signatures before compilation in class-to-casm. #10221
• Validate that entry-point builtins are in canonical order in class-to-casm. #10213

Corelib

• Breaking: removed the generated #[panic_with] wrapper functions (e.g. array_at, u128_from_felt252, u128_sub, u256_sub, and the u*_as_non_zero helpers) in favor of the _try_*/.expect(...) equivalents. #10095
• Made Encode::size_hint more exact. #10108

Formatter

• Sort merged use items via compare_names, and made use merging more consistent. #10123 #10150
• Don't glue a comment to { in an empty block. #10188
• Made cairofmt::skip work properly for additional items. #10220

Optimizations

• Stream the lexer with a lookahead window instead of cloning all tokens up front, reducing peak memory during parsing. #10141
• Keep syntax node ids stable across reparses (canonical roots, kind-keyed child index, parent-relative offsets), restoring salsa early cutoff for structure-preserving edits. #10105 #10190 #10191
• Cache external (plugin-generated) file content in the defs cache. #10164
• Track arrays as a bounded suffix behind a forgotten prefix in equality analysis, and keep tracking remainders popped through it. #10076 #10085
• Avoid cloning blocks and analysis info in inlining and dataflow. #10127
• Made substitute faster on empty substitutions. #10146
• Reduced intermediary string allocations across the compiler. #10124 #10125 #10126

Documentation

• Corrected corelib doc examples and comments: DivRem, keccak_u256s_be_inputs, get_curve_size, egcd's # Panics, Iterator::sum, byte-array example, and misc doc-comment fixes. #10092 #10100 #10101 #10102 #10106 #10122 #10152 #10204

Other

• Debug info: added parameter information to functions' debug info, and stabilized ids in the debug replacer. by @piotmag769 in #10225 #10187
• Dependency updates, including salsa. #10195 #10196

New Contributors

• @reflecttypefor made their first contribution in #10089
• @alaningtrump made their first contribution in #10185

Full Changelog: v2.19.0...v2.20.0