Update 2 syn (#1557)

We have not been receiving updates to syn for a while, because we are on
syn 1 still. Update to syn 2 and lift it into the workspace, which
requires revamping how several `proc_macro_attribute`s are parsed. In
the process, sprinkle pgrx-sql-entity-graph with paranoid amounts of
`track_caller`, expects, and compound errors on the unhappy path, to try
to make the code start producing useful error spans.

Then also drop unused features from some of our dependencies to
completely erase syn 1 from the dependency tree. We don't meddle with
any compressible sections, because we just look at exported symbols, not
debuginfo, so I believe this is inconsequential. It's acceptable to
revert that part of this change, however, if it doesn't actually work.

Removes 4 crates from the dependency tree

The syn changes include:
- `syn::LifetimeDef` is now `LifetimeParam`
- `syn::ImplItem::Method` is now `syn::ImplItem::Fn`
- `syn::ImplItemMethod` is now `syn::ImplItemFn`
- Type ascription && `syn::Expr::Type` no longer exist
- `syn::MetaNameValue` replaces its `lit` field with `value`, as it
accepts non-literals
- `syn::GenericArgument::Binding` is now `GenericArgument::AssocType`
- `syn::Attribute` hid its `path` field as `.path()`
- `syn::Attribute` hid its `token` field, so there is only `ToTokens`
- `syn::Attribute` changed how it structures access to its args. We now
parse inner args of a `syn::Attribute` for our proc-macro attributes
like `#[pg_operator]`, without considering parentheses.

Cargo.toml

@@ -60,7 +60,10 @@ cargo_toml = "0.16" # used for building projects
 eyre = "0.6.9" # simplifies error-handling
 libc = "0.2" # FFI compat
 owo-colors = "3.5" # for output highlighting
+proc-macro2 = { version = "1.0.78", features = [ "span-locations" ] }
+quote = "1.0.33"
 regex = "1.1" # used for build/test
+syn = { version = "2", features = [ "extra-traits", "full", "parsing" ] }
 thiserror = "1"
 unescape = "0.1.0" # for escaped-character-handling
 url = "2.4.1" # the non-existent std::web

cargo-pgrx/Cargo.toml

@@ -40,9 +40,9 @@ tempfile = "3.8.0"
 toml = "0.8.2" # our config files
 
 # SQL schema generation
-object = "0.32.1"
-proc-macro2 = { version = "1.0.69", features = [ "span-locations" ] }
-quote = "1.0.33"
+object = { version = "0.32.1", default-features = false, features = [ "std" ] }
+proc-macro2.workspace = true
+quote.workspace = true
 
 # emit better diagnostics
 color-eyre = "0.6.2"

pgrx-macros/Cargo.toml

@@ -34,9 +34,9 @@ no-schema-generation = ["pgrx-sql-entity-graph/no-schema-generation"]
 [dependencies]
 pgrx-sql-entity-graph.workspace = true
 
-proc-macro2 = "1.0.69"
-quote = "1.0.33"
-syn = { version = "1.0.109", features = [ "extra-traits", "full", "fold", "parsing" ] }
+proc-macro2.workspace = true
+quote.workspace = true
+syn.workspace = true
 
 
 [dev-dependencies]