Move some functions from `rustc_expand` to `rustc_builtin_macros`.

These functions are only used in `rustc_builtin_macros`, so it makes
sense for them to live there. This allows them to be changed from `pub`
to `pub(crate)`.

10 files changed, 225 insertions, 26 deletions

diff --git a/compiler/rustc_builtin_macros/src/asm.rs b/compiler/rustc_builtin_macros/src/asm.rs
index 137ac441579..49b1b8cf992 100644
--- a/compiler/rustc_builtin_macros/src/asm.rs
+++ b/compiler/rustc_builtin_macros/src/asm.rs
@@ -1,3 +1,5 @@
+use crate::errors;
+use crate::util::expr_to_spanned_string;
 use ast::token::IdentIsRaw;
 use rustc_ast as ast;
 use rustc_ast::ptr::P;
@@ -16,8 +18,6 @@ use rustc_span::{ErrorGuaranteed, InnerSpan, Span};
 use rustc_target::asm::InlineAsmArch;
 use smallvec::smallvec;
 
-use crate::errors;
-
 pub struct AsmArgs {
     pub templates: Vec<P<ast::Expr>>,
     pub operands: Vec<(ast::InlineAsmOperand, Span)>,
diff --git a/compiler/rustc_builtin_macros/src/compile_error.rs b/compiler/rustc_builtin_macros/src/compile_error.rs
index 2f2a87fc9aa..833e9cb5d75 100644
--- a/compiler/rustc_builtin_macros/src/compile_error.rs
+++ b/compiler/rustc_builtin_macros/src/compile_error.rs
@@ -1,7 +1,7 @@
 // The compiler code necessary to support the compile_error! extension.
 
+use crate::util::get_single_str_from_tts;
 use rustc_ast::tokenstream::TokenStream;
-use rustc_expand::base::get_single_str_from_tts;
 use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacroExpanderResult};
 use rustc_span::Span;
 
diff --git a/compiler/rustc_builtin_macros/src/concat.rs b/compiler/rustc_builtin_macros/src/concat.rs
index 93a7ac05a9b..125f4bc6dc4 100644
--- a/compiler/rustc_builtin_macros/src/concat.rs
+++ b/compiler/rustc_builtin_macros/src/concat.rs
@@ -1,12 +1,11 @@
+use crate::errors;
+use crate::util::get_exprs_from_tts;
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::{ExprKind, LitKind, UnOp};
-use rustc_expand::base::get_exprs_from_tts;
 use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacEager, MacroExpanderResult};
 use rustc_session::errors::report_lit_error;
 use rustc_span::symbol::Symbol;
 
-use crate::errors;
-
 pub fn expand_concat(
     cx: &mut ExtCtxt<'_>,
     sp: rustc_span::Span,
diff --git a/compiler/rustc_builtin_macros/src/concat_bytes.rs b/compiler/rustc_builtin_macros/src/concat_bytes.rs
index 45fec294578..f9d3f4a1425 100644
--- a/compiler/rustc_builtin_macros/src/concat_bytes.rs
+++ b/compiler/rustc_builtin_macros/src/concat_bytes.rs
@@ -1,11 +1,10 @@
+use crate::errors;
+use crate::util::get_exprs_from_tts;
 use rustc_ast::{ptr::P, token, tokenstream::TokenStream, ExprKind, LitIntType, LitKind, UintTy};
-use rustc_expand::base::get_exprs_from_tts;
 use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacEager, MacroExpanderResult};
 use rustc_session::errors::report_lit_error;
 use rustc_span::{ErrorGuaranteed, Span};
 
-use crate::errors;
-
 /// Emits errors for literal expressions that are invalid inside and outside of an array.
 fn invalid_type_err(
     cx: &ExtCtxt<'_>,
diff --git a/compiler/rustc_builtin_macros/src/env.rs b/compiler/rustc_builtin_macros/src/env.rs
index 93873045943..3903c77b669 100644
--- a/compiler/rustc_builtin_macros/src/env.rs
+++ b/compiler/rustc_builtin_macros/src/env.rs
@@ -3,10 +3,11 @@
 // interface.
 //
 
+use crate::errors;
+use crate::util::{expr_to_string, get_exprs_from_tts, get_single_str_from_tts};
 use rustc_ast::token::{self, LitKind};
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::{AstDeref, ExprKind, GenericArg, Mutability};
-use rustc_expand::base::{expr_to_string, get_exprs_from_tts, get_single_str_from_tts};
 use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacEager, MacroExpanderResult};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::Span;
@@ -14,8 +15,6 @@ use std::env;
 use std::env::VarError;
 use thin_vec::thin_vec;
 
-use crate::errors;
-
 fn lookup_env<'cx>(cx: &'cx ExtCtxt<'_>, var: Symbol) -> Result<Symbol, VarError> {
     let var = var.as_str();
     if let Some(value) = cx.sess.opts.logical_env.get(var) {
diff --git a/compiler/rustc_builtin_macros/src/errors.rs b/compiler/rustc_builtin_macros/src/errors.rs
index 6b6647ef085..055ff79a8ad 100644
--- a/compiler/rustc_builtin_macros/src/errors.rs
+++ b/compiler/rustc_builtin_macros/src/errors.rs
@@ -842,3 +842,26 @@ pub(crate) struct ExpectedRegisterClassOrExplicitRegister {
     #[primary_span]
     pub(crate) span: Span,
 }
+
+#[derive(Diagnostic)]
+#[diag(builtin_macros_expected_comma_in_list)]
+pub(crate) struct ExpectedCommaInList {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(builtin_macros_only_one_argument)]
+pub(crate) struct OnlyOneArgument<'a> {
+    #[primary_span]
+    pub span: Span,
+    pub name: &'a str,
+}
+
+#[derive(Diagnostic)]
+#[diag(builtin_macros_takes_no_arguments)]
+pub(crate) struct TakesNoArguments<'a> {
+    #[primary_span]
+    pub span: Span,
+    pub name: &'a str,
+}
diff --git a/compiler/rustc_builtin_macros/src/format.rs b/compiler/rustc_builtin_macros/src/format.rs
index 51d6058a744..3f44096714c 100644
--- a/compiler/rustc_builtin_macros/src/format.rs
+++ b/compiler/rustc_builtin_macros/src/format.rs
@@ -1,3 +1,5 @@
+use crate::errors;
+use crate::util::expr_to_spanned_string;
 use parse::Position::ArgumentNamed;
 use rustc_ast::ptr::P;
 use rustc_ast::tokenstream::TokenStream;
@@ -10,14 +12,13 @@ use rustc_ast::{
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{Applicability, Diag, MultiSpan, PResult, SingleLabelManySpans};
 use rustc_expand::base::*;
+use rustc_lint_defs::builtin::NAMED_ARGUMENTS_USED_POSITIONALLY;
+use rustc_lint_defs::{BufferedEarlyLint, BuiltinLintDiag, LintId};
 use rustc_parse::parser::Recovered;
 use rustc_parse_format as parse;
 use rustc_span::symbol::{Ident, Symbol};
 use rustc_span::{BytePos, ErrorGuaranteed, InnerSpan, Span};
 
-use rustc_lint_defs::builtin::NAMED_ARGUMENTS_USED_POSITIONALLY;
-use rustc_lint_defs::{BufferedEarlyLint, BuiltinLintDiag, LintId};
-
 // The format_args!() macro is expanded in three steps:
 //  1. First, `parse_args` will parse the `(literal, arg, arg, name=arg, name=arg)` syntax,
 //     but doesn't parse the template (the literal) itself.
@@ -38,8 +39,6 @@ enum PositionUsedAs {
 }
 use PositionUsedAs::*;
 
-use crate::errors;
-
 #[derive(Debug)]
 struct MacroInput {
     fmtstr: P<Expr>,
diff --git a/compiler/rustc_builtin_macros/src/lib.rs b/compiler/rustc_builtin_macros/src/lib.rs
index 56a72432689..7c7b9c2d65f 100644
--- a/compiler/rustc_builtin_macros/src/lib.rs
+++ b/compiler/rustc_builtin_macros/src/lib.rs
@@ -50,13 +50,13 @@ mod pattern_type;
 mod source_util;
 mod test;
 mod trace_macros;
-mod util;
 
 pub mod asm;
 pub mod cmdline_attrs;
 pub mod proc_macro_harness;
 pub mod standard_library_imports;
 pub mod test_harness;
+pub mod util;
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
diff --git a/compiler/rustc_builtin_macros/src/source_util.rs b/compiler/rustc_builtin_macros/src/source_util.rs
index c79ae716806..033c7446b26 100644
--- a/compiler/rustc_builtin_macros/src/source_util.rs
+++ b/compiler/rustc_builtin_macros/src/source_util.rs
@@ -1,3 +1,6 @@
+use crate::util::{
+    check_zero_tts, get_single_str_from_tts, get_single_str_spanned_from_tts, parse_expr,
+};
 use rustc_ast as ast;
 use rustc_ast::ptr::P;
 use rustc_ast::token;
@@ -5,11 +8,8 @@ use rustc_ast::tokenstream::TokenStream;
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::sync::Lrc;
 use rustc_expand::base::{
-    check_zero_tts, get_single_str_from_tts, get_single_str_spanned_from_tts, parse_expr,
-    resolve_path,
+    resolve_path, DummyResult, ExpandResult, ExtCtxt, MacEager, MacResult, MacroExpanderResult,
 };
-use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt};
-use rustc_expand::base::{MacEager, MacResult, MacroExpanderResult};
 use rustc_expand::module::DirOwnership;
 use rustc_parse::new_parser_from_file;
 use rustc_parse::parser::{ForceCollect, Parser};
diff --git a/compiler/rustc_builtin_macros/src/util.rs b/compiler/rustc_builtin_macros/src/util.rs
index ad6b09ba574..49687c6a0ad 100644
--- a/compiler/rustc_builtin_macros/src/util.rs
+++ b/compiler/rustc_builtin_macros/src/util.rs
@@ -1,9 +1,14 @@
-use rustc_ast::{attr, AttrStyle, Attribute, MetaItem};
-use rustc_expand::base::{Annotatable, ExtCtxt};
+use crate::errors;
+use rustc_ast::tokenstream::TokenStream;
+use rustc_ast::{self as ast, attr, ptr::P, token, AttrStyle, Attribute, MetaItem};
+use rustc_errors::{Applicability, Diag, ErrorGuaranteed};
+use rustc_expand::base::{Annotatable, ExpandResult, ExtCtxt};
+use rustc_expand::expand::AstFragment;
 use rustc_feature::AttributeTemplate;
 use rustc_lint_defs::builtin::DUPLICATE_MACRO_ATTRIBUTES;
-use rustc_parse::validate_attr;
-use rustc_span::Symbol;
+use rustc_parse::{parser, validate_attr};
+use rustc_session::errors::report_lit_error;
+use rustc_span::{BytePos, Span, Symbol};
 
 pub fn check_builtin_macro_attribute(ecx: &ExtCtxt<'_>, meta_item: &MetaItem, name: Symbol) {
     // All the built-in macro attributes are "words" at the moment.
@@ -46,3 +51,178 @@ pub fn warn_on_duplicate_attribute(ecx: &ExtCtxt<'_>, item: &Annotatable, name:
         }
     }
 }
+
+/// `Ok` represents successfully retrieving the string literal at the correct
+/// position, e.g., `println("abc")`.
+type ExprToSpannedStringResult<'a> = Result<(Symbol, ast::StrStyle, Span), UnexpectedExprKind<'a>>;
+
+/// - `Ok` is returned when the conversion to a string literal is unsuccessful,
+/// but another type of expression is obtained instead.
+/// - `Err` is returned when the conversion process fails.
+type UnexpectedExprKind<'a> = Result<(Diag<'a>, bool /* has_suggestions */), ErrorGuaranteed>;
+
+/// Extracts a string literal from the macro expanded version of `expr`,
+/// returning a diagnostic error of `err_msg` if `expr` is not a string literal.
+/// The returned bool indicates whether an applicable suggestion has already been
+/// added to the diagnostic to avoid emitting multiple suggestions. `Err(Err(ErrorGuaranteed))`
+/// indicates that an ast error was encountered.
+// FIXME(Nilstrieb) Make this function setup translatable
+#[allow(rustc::untranslatable_diagnostic)]
+pub(crate) fn expr_to_spanned_string<'a>(
+    cx: &'a mut ExtCtxt<'_>,
+    expr: P<ast::Expr>,
+    err_msg: &'static str,
+) -> ExpandResult<ExprToSpannedStringResult<'a>, ()> {
+    if !cx.force_mode
+        && let ast::ExprKind::MacCall(m) = &expr.kind
+        && cx.resolver.macro_accessible(cx.current_expansion.id, &m.path).is_err()
+    {
+        return ExpandResult::Retry(());
+    }
+
+    // Perform eager expansion on the expression.
+    // We want to be able to handle e.g., `concat!("foo", "bar")`.
+    let expr = cx.expander().fully_expand_fragment(AstFragment::Expr(expr)).make_expr();
+
+    ExpandResult::Ready(Err(match expr.kind {
+        ast::ExprKind::Lit(token_lit) => match ast::LitKind::from_token_lit(token_lit) {
+            Ok(ast::LitKind::Str(s, style)) => {
+                return ExpandResult::Ready(Ok((s, style, expr.span)));
+            }
+            Ok(ast::LitKind::ByteStr(..)) => {
+                let mut err = cx.dcx().struct_span_err(expr.span, err_msg);
+                let span = expr.span.shrink_to_lo();
+                err.span_suggestion(
+                    span.with_hi(span.lo() + BytePos(1)),
+                    "consider removing the leading `b`",
+                    "",
+                    Applicability::MaybeIncorrect,
+                );
+                Ok((err, true))
+            }
+            Ok(ast::LitKind::Err(guar)) => Err(guar),
+            Err(err) => Err(report_lit_error(&cx.sess.psess, err, token_lit, expr.span)),
+            _ => Ok((cx.dcx().struct_span_err(expr.span, err_msg), false)),
+        },
+        ast::ExprKind::Err(guar) => Err(guar),
+        ast::ExprKind::Dummy => {
+            cx.dcx().span_bug(expr.span, "tried to get a string literal from `ExprKind::Dummy`")
+        }
+        _ => Ok((cx.dcx().struct_span_err(expr.span, err_msg), false)),
+    }))
+}
+
+/// Extracts a string literal from the macro expanded version of `expr`,
+/// emitting `err_msg` if `expr` is not a string literal. This does not stop
+/// compilation on error, merely emits a non-fatal error and returns `Err`.
+pub(crate) fn expr_to_string(
+    cx: &mut ExtCtxt<'_>,
+    expr: P<ast::Expr>,
+    err_msg: &'static str,
+) -> ExpandResult<Result<(Symbol, ast::StrStyle), ErrorGuaranteed>, ()> {
+    expr_to_spanned_string(cx, expr, err_msg).map(|res| {
+        res.map_err(|err| match err {
+            Ok((err, _)) => err.emit(),
+            Err(guar) => guar,
+        })
+        .map(|(symbol, style, _)| (symbol, style))
+    })
+}
+
+/// Non-fatally assert that `tts` is empty. Note that this function
+/// returns even when `tts` is non-empty, macros that *need* to stop
+/// compilation should call `cx.diagnostic().abort_if_errors()`
+/// (this should be done as rarely as possible).
+pub(crate) fn check_zero_tts(cx: &ExtCtxt<'_>, span: Span, tts: TokenStream, name: &str) {
+    if !tts.is_empty() {
+        cx.dcx().emit_err(errors::TakesNoArguments { span, name });
+    }
+}
+
+/// Parse an expression. On error, emit it, advancing to `Eof`, and return `Err`.
+pub(crate) fn parse_expr(p: &mut parser::Parser<'_>) -> Result<P<ast::Expr>, ErrorGuaranteed> {
+    let guar = match p.parse_expr() {
+        Ok(expr) => return Ok(expr),
+        Err(err) => err.emit(),
+    };
+    while p.token != token::Eof {
+        p.bump();
+    }
+    Err(guar)
+}
+
+/// Interpreting `tts` as a comma-separated sequence of expressions,
+/// expect exactly one string literal, or emit an error and return `Err`.
+pub(crate) fn get_single_str_from_tts(
+    cx: &mut ExtCtxt<'_>,
+    span: Span,
+    tts: TokenStream,
+    name: &str,
+) -> ExpandResult<Result<Symbol, ErrorGuaranteed>, ()> {
+    get_single_str_spanned_from_tts(cx, span, tts, name).map(|res| res.map(|(s, _)| s))
+}
+
+pub(crate) fn get_single_str_spanned_from_tts(
+    cx: &mut ExtCtxt<'_>,
+    span: Span,
+    tts: TokenStream,
+    name: &str,
+) -> ExpandResult<Result<(Symbol, Span), ErrorGuaranteed>, ()> {
+    let mut p = cx.new_parser_from_tts(tts);
+    if p.token == token::Eof {
+        let guar = cx.dcx().emit_err(errors::OnlyOneArgument { span, name });
+        return ExpandResult::Ready(Err(guar));
+    }
+    let ret = match parse_expr(&mut p) {
+        Ok(ret) => ret,
+        Err(guar) => return ExpandResult::Ready(Err(guar)),
+    };
+    let _ = p.eat(&token::Comma);
+
+    if p.token != token::Eof {
+        cx.dcx().emit_err(errors::OnlyOneArgument { span, name });
+    }
+    expr_to_spanned_string(cx, ret, "argument must be a string literal").map(|res| {
+        res.map_err(|err| match err {
+            Ok((err, _)) => err.emit(),
+            Err(guar) => guar,
+        })
+        .map(|(symbol, _style, span)| (symbol, span))
+    })
+}
+
+/// Extracts comma-separated expressions from `tts`.
+/// On error, emit it, and return `Err`.
+pub(crate) fn get_exprs_from_tts(
+    cx: &mut ExtCtxt<'_>,
+    tts: TokenStream,
+) -> ExpandResult<Result<Vec<P<ast::Expr>>, ErrorGuaranteed>, ()> {
+    let mut p = cx.new_parser_from_tts(tts);
+    let mut es = Vec::new();
+    while p.token != token::Eof {
+        let expr = match parse_expr(&mut p) {
+            Ok(expr) => expr,
+            Err(guar) => return ExpandResult::Ready(Err(guar)),
+        };
+        if !cx.force_mode
+            && let ast::ExprKind::MacCall(m) = &expr.kind
+            && cx.resolver.macro_accessible(cx.current_expansion.id, &m.path).is_err()
+        {
+            return ExpandResult::Retry(());
+        }
+
+        // Perform eager expansion on the expression.
+        // We want to be able to handle e.g., `concat!("foo", "bar")`.
+        let expr = cx.expander().fully_expand_fragment(AstFragment::Expr(expr)).make_expr();
+
+        es.push(expr);
+        if p.eat(&token::Comma) {
+            continue;
+        }
+        if p.token != token::Eof {
+            let guar = cx.dcx().emit_err(errors::ExpectedCommaInList { span: p.token.span });
+            return ExpandResult::Ready(Err(guar));
+        }
+    }
+    ExpandResult::Ready(Ok(es))
+}