diff options
Diffstat (limited to 'compiler/rustc_pattern_analysis/src/rustc/print.rs')
| -rw-r--r-- | compiler/rustc_pattern_analysis/src/rustc/print.rs | 219 |
1 files changed, 219 insertions, 0 deletions
diff --git a/compiler/rustc_pattern_analysis/src/rustc/print.rs b/compiler/rustc_pattern_analysis/src/rustc/print.rs new file mode 100644 index 00000000000..7d638714605 --- /dev/null +++ b/compiler/rustc_pattern_analysis/src/rustc/print.rs @@ -0,0 +1,219 @@ +//! Pattern analysis sometimes wants to print patterns as part of a user-visible +//! diagnostic. +//! +//! Historically it did so by creating a synthetic [`thir::Pat`](rustc_middle::thir::Pat) +//! and printing that, but doing so was making it hard to modify the THIR pattern +//! representation for other purposes. +//! +//! So this module contains a forked copy of `thir::Pat` that is used _only_ +//! for diagnostics, and has been partly simplified to remove things that aren't +//! needed for printing. + +use std::fmt; + +use rustc_middle::thir::PatRange; +use rustc_middle::ty::{self, AdtDef, Ty, TyCtxt}; +use rustc_middle::{bug, mir}; +use rustc_span::sym; +use rustc_target::abi::{FieldIdx, VariantIdx}; + +#[derive(Clone, Debug)] +pub(crate) struct FieldPat<'tcx> { + pub(crate) field: FieldIdx, + pub(crate) pattern: Box<Pat<'tcx>>, +} + +#[derive(Clone, Debug)] +pub(crate) struct Pat<'tcx> { + pub(crate) ty: Ty<'tcx>, + pub(crate) kind: PatKind<'tcx>, +} + +#[derive(Clone, Debug)] +pub(crate) enum PatKind<'tcx> { + Wild, + + StructLike { + enum_info: EnumInfo<'tcx>, + subpatterns: Vec<FieldPat<'tcx>>, + }, + + Box { + subpattern: Box<Pat<'tcx>>, + }, + + Deref { + subpattern: Box<Pat<'tcx>>, + }, + + Constant { + value: mir::Const<'tcx>, + }, + + Range(Box<PatRange<'tcx>>), + + Slice { + prefix: Box<[Box<Pat<'tcx>>]>, + /// True if this slice-like pattern should include a `..` between the + /// prefix and suffix. + has_dot_dot: bool, + suffix: Box<[Box<Pat<'tcx>>]>, + }, + + Never, +} + +impl<'tcx> fmt::Display for Pat<'tcx> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + match self.kind { + PatKind::Wild => write!(f, "_"), + PatKind::Never => write!(f, "!"), + PatKind::Box { ref subpattern } => write!(f, "box {subpattern}"), + PatKind::StructLike { ref enum_info, ref subpatterns } => { + ty::tls::with(|tcx| write_struct_like(f, tcx, self.ty, enum_info, subpatterns)) + } + PatKind::Deref { ref subpattern } => write_ref_like(f, self.ty, subpattern), + PatKind::Constant { value } => write!(f, "{value}"), + PatKind::Range(ref range) => write!(f, "{range}"), + PatKind::Slice { ref prefix, has_dot_dot, ref suffix } => { + write_slice_like(f, prefix, has_dot_dot, suffix) + } + } + } +} + +/// Returns a closure that will return `""` when called the first time, +/// and then return `", "` when called any subsequent times. +/// Useful for printing comma-separated lists. +fn start_or_comma() -> impl FnMut() -> &'static str { + let mut first = true; + move || { + if first { + first = false; + "" + } else { + ", " + } + } +} + +#[derive(Clone, Debug)] +pub(crate) enum EnumInfo<'tcx> { + Enum { adt_def: AdtDef<'tcx>, variant_index: VariantIdx }, + NotEnum, +} + +fn write_struct_like<'tcx>( + f: &mut impl fmt::Write, + tcx: TyCtxt<'_>, + ty: Ty<'tcx>, + enum_info: &EnumInfo<'tcx>, + subpatterns: &[FieldPat<'tcx>], +) -> fmt::Result { + let variant_and_name = match *enum_info { + EnumInfo::Enum { adt_def, variant_index } => { + let variant = adt_def.variant(variant_index); + let adt_did = adt_def.did(); + let name = if tcx.is_diagnostic_item(sym::Option, adt_did) + || tcx.is_diagnostic_item(sym::Result, adt_did) + { + variant.name.to_string() + } else { + format!("{}::{}", tcx.def_path_str(adt_def.did()), variant.name) + }; + Some((variant, name)) + } + EnumInfo::NotEnum => ty.ty_adt_def().and_then(|adt_def| { + Some((adt_def.non_enum_variant(), tcx.def_path_str(adt_def.did()))) + }), + }; + + let mut start_or_comma = start_or_comma(); + + if let Some((variant, name)) = &variant_and_name { + write!(f, "{name}")?; + + // Only for Adt we can have `S {...}`, + // which we handle separately here. + if variant.ctor.is_none() { + write!(f, " {{ ")?; + + let mut printed = 0; + for p in subpatterns { + if let PatKind::Wild = p.pattern.kind { + continue; + } + let name = variant.fields[p.field].name; + write!(f, "{}{}: {}", start_or_comma(), name, p.pattern)?; + printed += 1; + } + + let is_union = ty.ty_adt_def().is_some_and(|adt| adt.is_union()); + if printed < variant.fields.len() && (!is_union || printed == 0) { + write!(f, "{}..", start_or_comma())?; + } + + return write!(f, " }}"); + } + } + + let num_fields = variant_and_name.as_ref().map_or(subpatterns.len(), |(v, _)| v.fields.len()); + if num_fields != 0 || variant_and_name.is_none() { + write!(f, "(")?; + for i in 0..num_fields { + write!(f, "{}", start_or_comma())?; + + // Common case: the field is where we expect it. + if let Some(p) = subpatterns.get(i) { + if p.field.index() == i { + write!(f, "{}", p.pattern)?; + continue; + } + } + + // Otherwise, we have to go looking for it. + if let Some(p) = subpatterns.iter().find(|p| p.field.index() == i) { + write!(f, "{}", p.pattern)?; + } else { + write!(f, "_")?; + } + } + write!(f, ")")?; + } + + Ok(()) +} + +fn write_ref_like<'tcx>( + f: &mut impl fmt::Write, + ty: Ty<'tcx>, + subpattern: &Pat<'tcx>, +) -> fmt::Result { + match ty.kind() { + ty::Ref(_, _, mutbl) => { + write!(f, "&{}", mutbl.prefix_str())?; + } + _ => bug!("{ty} is a bad ref pattern type"), + } + write!(f, "{subpattern}") +} + +fn write_slice_like<'tcx>( + f: &mut impl fmt::Write, + prefix: &[Box<Pat<'tcx>>], + has_dot_dot: bool, + suffix: &[Box<Pat<'tcx>>], +) -> fmt::Result { + let mut start_or_comma = start_or_comma(); + write!(f, "[")?; + for p in prefix.iter() { + write!(f, "{}{}", start_or_comma(), p)?; + } + if has_dot_dot { + write!(f, "{}..", start_or_comma())?; + } + for p in suffix.iter() { + write!(f, "{}{}", start_or_comma(), p)?; + } + write!(f, "]") +} |