Open up visibility of starlark-syntax

Summary:
# Goal

One of the wins from having this as a separate extension is that we can customize the lint warnings for Sandcastle-specific codesmells.

# This diff

This is an RFC/POC for a very simple one: no `entry_point` called outside of the top-level.

To get this to work, I needed to make some changes to the visibility of things. See [this discussion](https://fb.workplace.com/groups/starlark/permalink/1547671819254974/) for context -- but *tldr;* is that a lot of the AST-manipulation/traversal stuff in `starlark_syntax` is hidden away.

The changes I made are to:
- Expose a `statements()` getter on `AstModule`
- Remove the visibility rule on `starlark_syntax`, making it available for use outside of `starlark-rust`

These were both needed because I want to specifically manipulate the Starlark AST (ie. traverse things the bodies of function definitions). See how I use them in D67765416.

The hope is that these changes are amenable for the maintainers for `starlark-rust` --
obviously I'm open to suggestions for other approaches as well.

Reviewed By: JakobDegen

Differential Revision: D67611206

fbshipit-source-id: d577f1886ff190d191f3c55022f9d485f6eb03be

starlark/src/analysis/find_call_name.rs

@@ -21,7 +21,6 @@ use starlark_syntax::syntax::ast::Argument;
 use starlark_syntax::syntax::ast::AstExpr;
 use starlark_syntax::syntax::ast::AstLiteral;
 use starlark_syntax::syntax::ast::Expr;
-use starlark_syntax::syntax::module::AstModuleFields;
 
 use crate::codemap::Span;
 use crate::codemap::Spanned;

starlark/src/syntax.rs

@@ -19,5 +19,6 @@
 
 pub use starlark_syntax::dialect::Dialect;
 pub use starlark_syntax::dialect::DialectTypes;
+pub use starlark_syntax::syntax::ast;
 pub use starlark_syntax::syntax::AstLoad;
 pub use starlark_syntax::syntax::AstModule;

starlark_lsp/src/bind.rs

@@ -38,7 +38,6 @@ use starlark_syntax::syntax::ast::ForP;
 use starlark_syntax::syntax::ast::IdentP;
 use starlark_syntax::syntax::ast::LambdaP;
 use starlark_syntax::syntax::ast::Stmt;
-use starlark_syntax::syntax::module::AstModuleFields;
 
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub(crate) enum Assigner {

starlark_lsp/src/loaded.rs

@@ -18,7 +18,6 @@
 use dupe::Dupe;
 use starlark::syntax::AstModule;
 use starlark_syntax::syntax::ast::StmtP;
-use starlark_syntax::syntax::module::AstModuleFields;
 use starlark_syntax::syntax::top_level_stmts::top_level_stmts;
 
 /// A loaded symbol. Returned from [`AstModule::loaded_symbols`].

starlark_syntax/src/syntax/module.rs

@@ -296,6 +296,11 @@ impl AstModule {
         self.codemap.file_span(x)
     }
 
+    /// Get back the AST statement for the module
+    pub fn statement(&self) -> &AstStmt {
+        &self.statement
+    }
+
     /// Locations where statements occur.
     pub fn stmt_locations(&self) -> Vec<FileSpan> {
         fn go(x: &AstStmt, codemap: &CodeMap, res: &mut Vec<FileSpan>) {