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Diffstat (limited to 'dhall/src/semantics/resolve/resolve.rs')
| -rw-r--r-- | dhall/src/semantics/resolve/resolve.rs | 231 |
1 files changed, 231 insertions, 0 deletions
diff --git a/dhall/src/semantics/resolve/resolve.rs b/dhall/src/semantics/resolve/resolve.rs new file mode 100644 index 0000000..82800ec --- /dev/null +++ b/dhall/src/semantics/resolve/resolve.rs @@ -0,0 +1,231 @@ +use std::borrow::Cow; +use std::path::{Path, PathBuf}; + +use crate::error::ErrorBuilder; +use crate::error::{Error, ImportError}; +use crate::semantics::{mkerr, Hir, HirKind, ImportEnv, NameEnv, Type}; +use crate::syntax; +use crate::syntax::{BinOp, Expr, ExprKind, FilePath, ImportLocation, URL}; +use crate::{Parsed, ParsedExpr, Resolved}; + +// TODO: evaluate import headers +pub(crate) type Import = syntax::Import<()>; + +/// Owned Hir with a type. Different from Tir because the Hir is owned. +pub(crate) type TypedHir = (Hir, Type); + +/// A root from which to resolve relative imports. +#[derive(Debug, Clone, PartialEq, Eq)] +pub(crate) enum ImportRoot { + LocalDir(PathBuf), +} + +fn resolve_one_import( + env: &mut ImportEnv, + import: &Import, + root: &ImportRoot, +) -> Result<TypedHir, Error> { + use self::ImportRoot::*; + use syntax::FilePrefix::*; + use syntax::ImportLocation::*; + let cwd = match root { + LocalDir(cwd) => cwd, + }; + match &import.location { + Local(prefix, path) => { + let path_buf: PathBuf = path.file_path.iter().collect(); + let path_buf = match prefix { + // TODO: fail gracefully + Parent => cwd.parent().unwrap().join(path_buf), + Here => cwd.join(path_buf), + _ => unimplemented!("{:?}", import), + }; + Ok(load_import(env, &path_buf)?) + } + _ => unimplemented!("{:?}", import), + } +} + +fn load_import(env: &mut ImportEnv, f: &Path) -> Result<TypedHir, Error> { + let parsed = Parsed::parse_file(f)?; + let typed = resolve_with_env(env, parsed)?.typecheck()?; + Ok((typed.normalize().to_hir(), typed.ty().clone())) +} + +/// Desugar the first level of the expression. +fn desugar(expr: &Expr) -> Cow<'_, Expr> { + match expr.kind() { + ExprKind::Completion(ty, compl) => { + let ty_field_default = Expr::new( + ExprKind::Field(ty.clone(), "default".into()), + expr.span(), + ); + let merged = Expr::new( + ExprKind::BinOp( + BinOp::RightBiasedRecordMerge, + ty_field_default, + compl.clone(), + ), + expr.span(), + ); + let ty_field_type = Expr::new( + ExprKind::Field(ty.clone(), "Type".into()), + expr.span(), + ); + Cow::Owned(Expr::new( + ExprKind::Annot(merged, ty_field_type), + expr.span(), + )) + } + _ => Cow::Borrowed(expr), + } +} + +/// Traverse the expression, handling import alternatives and passing +/// found imports to the provided function. Also resolving names. +fn traverse_resolve_expr( + name_env: &mut NameEnv, + expr: &Expr, + f: &mut impl FnMut(Import) -> Result<TypedHir, Error>, +) -> Result<Hir, Error> { + let expr = desugar(expr); + Ok(match expr.kind() { + ExprKind::Var(var) => match name_env.unlabel_var(&var) { + Some(v) => Hir::new(HirKind::Var(v), expr.span()), + None => mkerr( + ErrorBuilder::new(format!("unbound variable `{}`", var)) + .span_err(expr.span(), "not found in this scope") + .format(), + )?, + }, + ExprKind::BinOp(BinOp::ImportAlt, l, r) => { + match traverse_resolve_expr(name_env, l, f) { + Ok(l) => l, + Err(_) => { + match traverse_resolve_expr(name_env, r, f) { + Ok(r) => r, + // TODO: keep track of the other error too + Err(e) => return Err(e), + } + } + } + } + kind => { + let kind = kind.traverse_ref_maybe_binder(|l, e| { + if let Some(l) = l { + name_env.insert_mut(l); + } + let hir = traverse_resolve_expr(name_env, e, f)?; + if let Some(_) = l { + name_env.remove_mut(); + } + Ok::<_, Error>(hir) + })?; + let kind = match kind { + ExprKind::Import(import) => { + // TODO: evaluate import headers + let import = import.traverse_ref(|_| Ok::<_, Error>(()))?; + let imported = f(import)?; + HirKind::Import(imported.0, imported.1) + } + kind => HirKind::Expr(kind), + }; + Hir::new(kind, expr.span()) + } + }) +} + +fn resolve_with_env( + env: &mut ImportEnv, + parsed: Parsed, +) -> Result<Resolved, Error> { + let Parsed(expr, root) = parsed; + let resolved = + traverse_resolve_expr(&mut NameEnv::new(), &expr, &mut |import| { + env.handle_import(import, |env, import| { + resolve_one_import(env, import, &root) + }) + })?; + Ok(Resolved(resolved)) +} + +pub(crate) fn resolve(parsed: Parsed) -> Result<Resolved, Error> { + resolve_with_env(&mut ImportEnv::new(), parsed) +} + +pub(crate) fn skip_resolve(expr: &ParsedExpr) -> Result<Hir, Error> { + traverse_resolve_expr(&mut NameEnv::new(), expr, &mut |import| { + Err(ImportError::UnexpectedImport(import).into()) + }) +} + +pub trait Canonicalize { + fn canonicalize(&self) -> Self; +} + +impl Canonicalize for FilePath { + fn canonicalize(&self) -> FilePath { + let mut file_path = Vec::new(); + let mut file_path_components = self.file_path.clone().into_iter(); + + loop { + let component = file_path_components.next(); + match component.as_ref() { + // ─────────────────── + // canonicalize(ε) = ε + None => break, + + // canonicalize(directory₀) = directory₁ + // ─────────────────────────────────────── + // canonicalize(directory₀/.) = directory₁ + Some(c) if c == "." => continue, + + Some(c) if c == ".." => match file_path_components.next() { + // canonicalize(directory₀) = ε + // ──────────────────────────── + // canonicalize(directory₀/..) = /.. + None => file_path.push("..".to_string()), + + // canonicalize(directory₀) = directory₁/.. + // ────────────────────────────────────────────── + // canonicalize(directory₀/..) = directory₁/../.. + Some(ref c) if c == ".." => { + file_path.push("..".to_string()); + file_path.push("..".to_string()); + } + + // canonicalize(directory₀) = directory₁/component + // ─────────────────────────────────────────────── ; If "component" is not + // canonicalize(directory₀/..) = directory₁ ; ".." + Some(_) => continue, + }, + + // canonicalize(directory₀) = directory₁ + // ───────────────────────────────────────────────────────── ; If no other + // canonicalize(directory₀/component) = directory₁/component ; rule matches + Some(c) => file_path.push(c.clone()), + } + } + + FilePath { file_path } + } +} + +impl<SE: Copy> Canonicalize for ImportLocation<SE> { + fn canonicalize(&self) -> ImportLocation<SE> { + match self { + ImportLocation::Local(prefix, file) => { + ImportLocation::Local(*prefix, file.canonicalize()) + } + ImportLocation::Remote(url) => ImportLocation::Remote(URL { + scheme: url.scheme, + authority: url.authority.clone(), + path: url.path.canonicalize(), + query: url.query.clone(), + headers: url.headers.clone(), + }), + ImportLocation::Env(name) => ImportLocation::Env(name.to_string()), + ImportLocation::Missing => ImportLocation::Missing, + } + } +} |