Implement builtin#format_args, using rustc's format_args parser

crates/hir-def/Cargo.toml

@@ -33,6 +33,7 @@ triomphe.workspace = true
 
 rustc_abi = { version = "0.0.20221221", package = "hkalbasi-rustc-ap-rustc_abi", default-features = false }
 rustc_index = { version = "0.0.20221221", package = "hkalbasi-rustc-ap-rustc_index", default-features = false }
+rustc_lexer = { version = "0.1.0", package = "ra-ap-rustc_lexer" }
 
 # local deps
 stdx.workspace = true

crates/hir-def/src/body/lower.rs

@@ -29,9 +29,13 @@ use crate::{
     db::DefDatabase,
     expander::Expander,
     hir::{
-        dummy_expr_id, Array, Binding, BindingAnnotation, BindingId, BindingProblems, CaptureBy,
-        ClosureKind, Expr, ExprId, InlineAsm, Label, LabelId, Literal, LiteralOrConst, MatchArm,
-        Movability, OffsetOf, Pat, PatId, RecordFieldPat, RecordLitField, Statement,
+        dummy_expr_id,
+        format_args::{
+            self, FormatArgs, FormatArgument, FormatArgumentKind, FormatArgumentsCollector,
+        },
+        Array, Binding, BindingAnnotation, BindingId, BindingProblems, CaptureBy, ClosureKind,
+        Expr, ExprId, InlineAsm, Label, LabelId, Literal, LiteralOrConst, MatchArm, Movability,
+        OffsetOf, Pat, PatId, RecordFieldPat, RecordLitField, Statement,
     },
     item_scope::BuiltinShadowMode,
     lang_item::LangItem,
@@ -649,15 +653,58 @@ impl ExprCollector<'_> {
             }
             ast::Expr::UnderscoreExpr(_) => self.alloc_expr(Expr::Underscore, syntax_ptr),
             ast::Expr::AsmExpr(e) => {
-                let expr = Expr::InlineAsm(InlineAsm { e: self.collect_expr_opt(e.expr()) });
-                self.alloc_expr(expr, syntax_ptr)
+                let e = self.collect_expr_opt(e.expr());
+                self.alloc_expr(Expr::InlineAsm(InlineAsm { e }), syntax_ptr)
             }
             ast::Expr::OffsetOfExpr(e) => {
                 let container = Interned::new(TypeRef::from_ast_opt(&self.ctx(), e.ty()));
                 let fields = e.fields().map(|it| it.as_name()).collect();
                 self.alloc_expr(Expr::OffsetOf(OffsetOf { container, fields }), syntax_ptr)
             }
-            ast::Expr::FormatArgsExpr(_) => self.missing_expr(),
+            ast::Expr::FormatArgsExpr(f) => {
+                let mut args = FormatArgumentsCollector::new();
+                f.args().for_each(|arg| {
+                    args.add(FormatArgument {
+                        kind: match arg.name() {
+                            Some(name) => FormatArgumentKind::Named(name.as_name()),
+                            None => FormatArgumentKind::Normal,
+                        },
+                        expr: self.collect_expr_opt(arg.expr()),
+                    });
+                });
+                let template = f.template();
+                let fmt_snippet = template.as_ref().map(ToString::to_string);
+                let expr = self.collect_expr_opt(f.template());
+                if let Expr::Literal(Literal::String(_)) = self.body[expr] {
+                    let source = self.source_map.expr_map_back[expr].clone();
+                    let is_direct_literal = source.file_id == self.expander.current_file_id;
+                    if let ast::Expr::Literal(l) =
+                        source.value.to_node(&self.db.parse_or_expand(source.file_id))
+                    {
+                        if let ast::LiteralKind::String(s) = l.kind() {
+                            return Some(self.alloc_expr(
+                                Expr::FormatArgs(format_args::parse(
+                                    expr,
+                                    &s,
+                                    fmt_snippet,
+                                    args,
+                                    is_direct_literal,
+                                )),
+                                syntax_ptr,
+                            ));
+                        }
+                    }
+                }
+
+                self.alloc_expr(
+                    Expr::FormatArgs(FormatArgs {
+                        template_expr: expr,
+                        template: Default::default(),
+                        arguments: args.finish(),
+                    }),
+                    syntax_ptr,
+                )
+            }
         })
     }
 

crates/hir-def/src/body/pretty.rs

@@ -156,6 +156,11 @@ impl Printer<'_> {
             Expr::Missing => w!(self, "�"),
             Expr::Underscore => w!(self, "_"),
             Expr::InlineAsm(_) => w!(self, "builtin#asm(_)"),
+            Expr::FormatArgs(_fmt_args) => {
+                w!(self, "builtin#format_args(");
+                // FIXME
+                w!(self, ")");
+            }
             Expr::OffsetOf(offset_of) => {
                 w!(self, "builtin#offset_of(");
                 self.print_type_ref(&offset_of.container);

crates/hir-def/src/hir.rs

@@ -13,6 +13,7 @@
 //! See also a neighboring `body` module.
 
 pub mod type_ref;
+pub mod format_args;
 
 use std::fmt;
 
@@ -24,6 +25,7 @@ use syntax::ast;
 
 use crate::{
     builtin_type::{BuiltinFloat, BuiltinInt, BuiltinUint},
+    hir::format_args::{FormatArgs, FormatArgumentKind},
     path::{GenericArgs, Path},
     type_ref::{Mutability, Rawness, TypeRef},
     BlockId, ConstBlockId,
@@ -117,7 +119,6 @@ impl From<ast::LiteralKind> for Literal {
     fn from(ast_lit_kind: ast::LiteralKind) -> Self {
         use ast::LiteralKind;
         match ast_lit_kind {
-            // FIXME: these should have actual values filled in, but unsure on perf impact
             LiteralKind::IntNumber(lit) => {
                 if let builtin @ Some(_) = lit.suffix().and_then(BuiltinFloat::from_suffix) {
                     Literal::Float(
@@ -283,6 +284,7 @@ pub enum Expr {
     Underscore,
     OffsetOf(OffsetOf),
     InlineAsm(InlineAsm),
+    FormatArgs(FormatArgs),
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -355,7 +357,15 @@ impl Expr {
         match self {
             Expr::Missing => {}
             Expr::Path(_) | Expr::OffsetOf(_) => {}
-            Expr::InlineAsm(e) => f(e.e),
+            Expr::InlineAsm(it) => f(it.e),
+            Expr::FormatArgs(it) => {
+                f(it.template_expr);
+                it.arguments
+                    .arguments
+                    .iter()
+                    .filter(|it| !matches!(it.kind, FormatArgumentKind::Captured(_)))
+                    .for_each(|it| f(it.expr));
+            }
             Expr::If { condition, then_branch, else_branch } => {
                 f(*condition);
                 f(*then_branch);