diff options
Diffstat (limited to 'src/select.rs')
| -rw-r--r-- | src/select.rs | 77 |
1 files changed, 45 insertions, 32 deletions
diff --git a/src/select.rs b/src/select.rs index d20d2bc..f64944b 100644 --- a/src/select.rs +++ b/src/select.rs @@ -1,50 +1,55 @@ +use crate::SynResult; +use crate::TokenStream2; use proc_macro::TokenStream; -use proc_macro2::{Spacing, TokenStream as TokenStream2, TokenTree}; +use proc_macro2::{Spacing, TokenTree}; use quote::{ToTokens, quote}; use syn::parse::{Parse, ParseStream}; use syn::punctuated::Punctuated; use syn::{Expr, LitStr, Token, parse_macro_input}; -// ─── SelectArm ────────────────────────────────────────────────────────────────────────── - -/// A single arm inside `select!`. -pub enum SelectArm { +#[doc = include_str!("../doc/args/select_arm.md")] +pub enum SelectArmArgs { /// "feat_name" => expr Explicit { feat: LitStr, body: Expr }, + /// ! => expr Not { body: Expr }, + /// expr (no feature name — auto-detect by .await) Implicit { body: Expr }, } -impl Parse for SelectArm { - fn parse(input: ParseStream) -> syn::Result<Self> { +impl Parse for SelectArmArgs { + fn parse(input: ParseStream) -> SynResult<Self> { + // Try to parse an explicit feature name: "feature_name" => expr if input.peek(LitStr) { let feat: LitStr = input.parse()?; input.parse::<Token![=>]>()?; let body: Expr = input.parse()?; - Ok(SelectArm::Explicit { feat, body }) - } else if input.peek(Token![!]) { + Ok(SelectArmArgs::Explicit { feat, body }) + } + // Try to parse a negation arm: ! => expr + else if input.peek(Token![!]) { let _not: Token![!] = input.parse()?; input.parse::<Token![=>]>()?; let body: Expr = input.parse()?; - Ok(SelectArm::Not { body }) - } else { + Ok(SelectArmArgs::Not { body }) + } + // Otherwise treat as an implicit arm (auto-detect whether it contains .await) + else { let body: Expr = input.parse()?; - Ok(SelectArm::Implicit { body }) + Ok(SelectArmArgs::Implicit { body }) } } } -// ─── SelectInput ──────────────────────────────────────────────────────────────────────── - struct SelectInput { - arms: Vec<SelectArm>, + arms: Vec<SelectArmArgs>, } impl Parse for SelectInput { - fn parse(input: ParseStream) -> syn::Result<Self> { - let punctuated: Punctuated<SelectArm, Token![,]> = Punctuated::parse_terminated(input)?; + fn parse(input: ParseStream) -> SynResult<Self> { + let punctuated: Punctuated<SelectArmArgs, Token![,]> = Punctuated::parse_terminated(input)?; if punctuated.len() != 2 { return Err(syn::Error::new( @@ -53,13 +58,11 @@ impl Parse for SelectInput { )); } - let arms: Vec<SelectArm> = punctuated.into_iter().collect(); + let arms: Vec<SelectArmArgs> = punctuated.into_iter().collect(); Ok(SelectInput { arms }) } } -// ─── Select macro ─────────────────────────────────────────────────────────────────────── - pub(crate) fn select(input: TokenStream) -> TokenStream { let input = parse_macro_input!(input as SelectInput); let expanded = input.expand(); @@ -74,8 +77,8 @@ impl SelectInput { match (arm0, arm1) { // Both explicit — use cfg!() since no .await to worry about ( - SelectArm::Explicit { feat: f0, body: b0 }, - SelectArm::Explicit { feat: f1, body: b1 }, + SelectArmArgs::Explicit { feat: f0, body: b0 }, + SelectArmArgs::Explicit { feat: f1, body: b1 }, ) => { let f0_str = f0.value(); let f1_str = f1.value(); @@ -93,7 +96,7 @@ impl SelectInput { } // Explicit + Not — cfg!() safe (no .await) - (SelectArm::Explicit { feat, body }, SelectArm::Not { body: not_body }) => { + (SelectArmArgs::Explicit { feat, body }, SelectArmArgs::Not { body: not_body }) => { let feat_str = feat.value(); if has_not_prefix(&feat_str) { let inner = &feat_str[1..]; @@ -102,7 +105,9 @@ impl SelectInput { quote! { if cfg!(feature = #feat_str) { #body } else { #not_body } } } } - (SelectArm::Not { body: not_body }, SelectArm::Explicit { feat, body }) => { + + // Not + Explicit — cfg!() safe (no .await) + (SelectArmArgs::Not { body: not_body }, SelectArmArgs::Explicit { feat, body }) => { let feat_str = feat.value(); if has_not_prefix(&feat_str) { let inner = &feat_str[1..]; @@ -113,7 +118,10 @@ impl SelectInput { } // Explicit + Implicit — cfg!() safe (arms have no .await from this context) - (SelectArm::Explicit { feat, body }, SelectArm::Implicit { body: imp_body }) => { + ( + SelectArmArgs::Explicit { feat, body }, + SelectArmArgs::Implicit { body: imp_body }, + ) => { let feat_str = feat.value(); if has_not_prefix(&feat_str) { let inner = &feat_str[1..]; @@ -122,7 +130,12 @@ impl SelectInput { quote! { if cfg!(feature = #feat_str) { #body } else { #imp_body } } } } - (SelectArm::Implicit { body: imp_body }, SelectArm::Explicit { feat, body }) => { + + // Implicit + Explicit — cfg!() safe (arms have no .await from this context) + ( + SelectArmArgs::Implicit { body: imp_body }, + SelectArmArgs::Explicit { feat, body }, + ) => { let feat_str = feat.value(); if has_not_prefix(&feat_str) { let inner = &feat_str[1..]; @@ -133,7 +146,7 @@ impl SelectInput { } // Both implicit — use #[cfg] blocks to handle .await correctly - (SelectArm::Implicit { body: b0 }, SelectArm::Implicit { body: b1 }) => { + (SelectArmArgs::Implicit { body: b0 }, SelectArmArgs::Implicit { body: b1 }) => { let b0_has_await = token_stream_has_await(&b0.to_token_stream()); let b1_has_await = token_stream_has_await(&b1.to_token_stream()); @@ -152,15 +165,17 @@ impl SelectInput { } // Not + Implicit - (SelectArm::Not { body: not_body }, SelectArm::Implicit { body: imp_body }) => { + (SelectArmArgs::Not { body: not_body }, SelectArmArgs::Implicit { body: imp_body }) => { cfg_block("e! { #not_body }, "e! { #imp_body }) } - (SelectArm::Implicit { body: imp_body }, SelectArm::Not { body: not_body }) => { + + // Implicit + Not — use #[cfg] blocks to handle .await correctly + (SelectArmArgs::Implicit { body: imp_body }, SelectArmArgs::Not { body: not_body }) => { cfg_block("e! { #not_body }, "e! { #imp_body }) } // Two Not - (SelectArm::Not { body: b0 }, SelectArm::Not { body: b1 }) => { + (SelectArmArgs::Not { body: b0 }, SelectArmArgs::Not { body: b1 }) => { quote! { if cfg!(feature = "async") { #b0 } else { #b1 } } } } @@ -178,8 +193,6 @@ fn cfg_block(async_branch: &TokenStream2, sync_branch: &TokenStream2) -> TokenSt }} } -// ─── Helpers ───────────────────────────────────────────────────────────────────────────── - fn has_not_prefix(s: &str) -> bool { s.starts_with('!') } |