- Syntax extensions are replaced by proc macros.- Add rationale for why AST validation pass need to be run  post-expansion and why the pass is needed in the first place.

This commit was obtained by repeatedly inlining and simplifying.

…eneration method

It is only implemented for a single type. Directly passing this type issimpler and avoids overhead from indirect calls.

It can be retrieved from the Session too.

They are not representable by Cranelift

This commit too was obtained by repeatedly inlining and simplifying.

as request T-lang is requesting some major changes in the lint innerworkings inrust-lang#126768#issuecomment-2192634762

These table entries have wrong number of columns so the "notes" field ismissing from the rendered page. Fix by removing excess empty columns.

…ler-errorsVarious rustc_codegen_ssa cleanups

Add test for fn pointer duplication.I managed to make it fail when removing provenance checks in GVN.ccrust-lang#123670r? ``@oli-obk``

…docs, r=wesleywiserUpdate AST validation module docsDrive-by doc update for AST validation pass:- Syntax extensions are replaced by proc macros.- Add rationale for why AST validation pass need to be run  post-expansion and why the pass is needed in the first place.This was discussed during this week's [rustc-dev-guide reading club](https://rust-lang.zulipchat.com/#narrow/stream/196385-t-compiler.2Fwg-rustc-dev-guide), and the rationale was explained by cc ``@bjorn3.``

…atthewjasperSimplifications in match loweringA series of small simplifications and deduplications in the MIR lowering of patterns.r? ``@matthewjasper``

…ive, r=oli-obkAdd basic Serde serialization capabilities to Stable MIRThis PR adds basic Serde serialization capabilities to Stable MIR. It is intentionally minimal (just wrapping all stable MIR types with a Serde `derive`), so that any important design decisions can be discussed before going further. A simple test is included with this PR to validate that JSON can actually be emitted.## NotesWhen I wrapped the Stable MIR error types in `compiler/stable_mir/src/error.rs`, it caused test failures (though I'm not sure why) so I backed those out.## Future WorkSo, this PR will support serializing basic stable MIR, but it _does not_ support serializing interned values beneath `Ty`s and `AllocId`s, etc... My current thinking about how to handle this is as follows:1.  Add new `visited_X` fields to the `Tables` struct for each interned category of interest.2.  As serialization is occuring, serialize interned values as usual _and_ also record the interned value we referenced in `visited_X`.    (Possibly) In addition, if an interned value recursively references other interned values, record those interned values as well.3.  Teach the stable MIR `Context` how to access the `visited_X` values and expose them with wrappers in `stable_mir/src/lib.rs` to users (e.g. to serialize and/or further analyze them).### ProsThis approach does not commit to any specific serialization format regarding interned values or other more complex cases, which avoids us locking into any behaviors that may not be desired long-term.### ConsThe user will need to manually handle serializing interned values.### Alternatives1.  We can directly provide access to the underlying `Tables` maps for interned values; the disadvantage of this approach is that it either requires extra processing for users to filter out to only use the values that they need _or_ users may serialize extra values that they don't need. The advantage is that the implementation is even simpler. The other pros/cons are similar to the above.2.  We can directly serialize interned values by expanding them in-place. The pro is that this may make some basic inputs easier to consume. However, the cons are that there will need to be special provisions for dealing with cyclical values on both the producer and consumer _and_ global values will possibly need to be de-duplicated on the consumer side.

…=notriddleUpdate browser-ui-test version to `0.18.0`Should help withrust-lang#126436.r? ``@notriddle``

Switch back `non_local_definitions` lint to allow-by-defaultThis PR switch back (again) the `non_local_definitions` lint to allow-by-default as T-lang is requesting some (major) changes in the lint inner workings inrust-lang#126768 (comment).This PR will need to be beta-backported, as the lint is currently warn-by-default in beta.

…r=lqdFix Markdown tables in platform-support.mdThese table entries have wrong number of columns so the "notes" field is missing from the rendered page. Fix by removing excess empty columns.

… r=oli-obkEnable const casting for `f16` and `f128`I have an open PR to the Miri repo adding tests for this behaviorrust-lang/miri#3688, but that unfortunately hits the ICE path here. The changes seem reasonably low risk that it might be okay to merge separately from the tests, and I tested the result locally against an older version ofrust-lang/miri#3688.Cc ``@RalfJung``