bjoernager/rust
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proc_macro: Add an expand_expr method to TokenStream

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This feature is aimed at giving proc macros access to powers similar to
those used by builtin macros such as `format_args!` or `concat!`. These
macros are able to accept macros in place of string literal parameters,
such as the format string, as they perform recursive macro expansion
while being expanded.

This can be especially useful in many cases thanks to helper macros like
`concat!`, `stringify!` and `include_str!` which are often used to
construct string literals at compile-time in user code.

For now, this method only allows expanding macros which produce
literals, although more expresisons will be supported before the method
is stabilized.
This commit is contained in:
Nika Layzell 2021-07-18 15:53:06 -04:00
parent 800a156c1e
commit 3e4d3d2a29
8 changed files with 421 additions and 75 deletions
Download patch file Download diff file Expand all files Collapse all files

28
compiler/rustc_expand/src/proc_macro.rs
View file

@ -24,8 +24,9 @@ impl base::ProcMacro for BangProcMacro {
span: Span,
input: TokenStream,
) -> Result<TokenStream, ErrorReported> {
let proc_macro_backtrace = ecx.ecfg.proc_macro_backtrace;
let server = proc_macro_server::Rustc::new(ecx);
self.client.run(&EXEC_STRATEGY, server, input, ecx.ecfg.proc_macro_backtrace).map_err(|e| {
self.client.run(&EXEC_STRATEGY, server, input, proc_macro_backtrace).map_err(|e| {
let mut err = ecx.struct_span_err(span, "proc macro panicked");
if let Some(s) = e.as_str() {
err.help(&format!("message: {}", s));
@ -48,9 +49,10 @@ impl base::AttrProcMacro for AttrProcMacro {
annotation: TokenStream,
annotated: TokenStream,
) -> Result<TokenStream, ErrorReported> {
let proc_macro_backtrace = ecx.ecfg.proc_macro_backtrace;
let server = proc_macro_server::Rustc::new(ecx);
self.client
.run(&EXEC_STRATEGY, server, annotation, annotated, ecx.ecfg.proc_macro_backtrace)
.run(&EXEC_STRATEGY, server, annotation, annotated, proc_macro_backtrace)
.map_err(|e| {
let mut err = ecx.struct_span_err(span, "custom attribute panicked");
if let Some(s) = e.as_str() {
@ -97,19 +99,19 @@ impl MultiItemModifier for ProcMacroDerive {
nt_to_tokenstream(&item, &ecx.sess.parse_sess, CanSynthesizeMissingTokens::No)
};
let proc_macro_backtrace = ecx.ecfg.proc_macro_backtrace;
let server = proc_macro_server::Rustc::new(ecx);
let stream =
match self.client.run(&EXEC_STRATEGY, server, input, ecx.ecfg.proc_macro_backtrace) {
Ok(stream) => stream,
Err(e) => {
let mut err = ecx.struct_span_err(span, "proc-macro derive panicked");
if let Some(s) = e.as_str() {
err.help(&format!("message: {}", s));
}
err.emit();
return ExpandResult::Ready(vec![]);
let stream = match self.client.run(&EXEC_STRATEGY, server, input, proc_macro_backtrace) {
Ok(stream) => stream,
Err(e) => {
let mut err = ecx.struct_span_err(span, "proc-macro derive panicked");
if let Some(s) = e.as_str() {
err.help(&format!("message: {}", s));
}
};
err.emit();
return ExpandResult::Ready(vec![]);
}
};
let error_count_before = ecx.sess.parse_sess.span_diagnostic.err_count();
let mut parser =