Rollup merge of #121764 - Zoxc:incr-sess-no-source, r=oli-obk

Make incremental sessions identity no longer depend on the crate names provided by source code

This makes incremental sessions identity no longer depend on the crate names provided by source code, implementing
https://github.com/rust-lang/compiler-team/issues/726.

r? ````@oli-obk````

compiler/rustc_session/src/errors.rs

@@ -10,7 +10,7 @@ use rustc_macros::Diagnostic;
 use rustc_span::{Span, Symbol};
 use rustc_target::spec::{SplitDebuginfo, StackProtector, TargetTriple};
 
-use crate::parse::ParseSess;
+use crate::{config::CrateType, parse::ParseSess};
 
 pub struct FeatureGateError {
     pub span: MultiSpan,
@@ -345,6 +345,13 @@ pub(crate) struct BinaryFloatLiteralNotSupported {
     pub span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(session_unsupported_crate_type_for_target)]
+pub struct UnsupportedCrateTypeForTarget<'a> {
+    pub crate_type: CrateType,
+    pub target_triple: &'a TargetTriple,
+}
+
 pub fn report_lit_error(
     psess: &ParseSess,
     err: LitError,

compiler/rustc_session/src/output.rs

@@ -1,7 +1,7 @@
 //! Related to out filenames of compilation (e.g. binaries).
-use crate::config::{CrateType, Input, OutFileName, OutputFilenames, OutputType};
+use crate::config::{self, CrateType, Input, OutFileName, OutputFilenames, OutputType};
 use crate::errors::{
-    CrateNameDoesNotMatch, CrateNameEmpty, CrateNameInvalid, FileIsNotWriteable,
+    self, CrateNameDoesNotMatch, CrateNameEmpty, CrateNameInvalid, FileIsNotWriteable,
     InvalidCharacterInCrateName, InvalidCrateNameHelp,
 };
 use crate::Session;
@@ -200,3 +200,64 @@ pub fn invalid_output_for_target(sess: &Session, crate_type: CrateType) -> bool
 
     false
 }
+
+pub const CRATE_TYPES: &[(Symbol, CrateType)] = &[
+    (sym::rlib, CrateType::Rlib),
+    (sym::dylib, CrateType::Dylib),
+    (sym::cdylib, CrateType::Cdylib),
+    (sym::lib, config::default_lib_output()),
+    (sym::staticlib, CrateType::Staticlib),
+    (sym::proc_dash_macro, CrateType::ProcMacro),
+    (sym::bin, CrateType::Executable),
+];
+
+pub fn categorize_crate_type(s: Symbol) -> Option<CrateType> {
+    Some(CRATE_TYPES.iter().find(|(key, _)| *key == s)?.1)
+}
+
+pub fn collect_crate_types(session: &Session, attrs: &[ast::Attribute]) -> Vec<CrateType> {
+    // If we're generating a test executable, then ignore all other output
+    // styles at all other locations
+    if session.opts.test {
+        return vec![CrateType::Executable];
+    }
+
+    // Only check command line flags if present. If no types are specified by
+    // command line, then reuse the empty `base` Vec to hold the types that
+    // will be found in crate attributes.
+    // JUSTIFICATION: before wrapper fn is available
+    #[allow(rustc::bad_opt_access)]
+    let mut base = session.opts.crate_types.clone();
+    if base.is_empty() {
+        let attr_types = attrs.iter().filter_map(|a| {
+            if a.has_name(sym::crate_type)
+                && let Some(s) = a.value_str()
+            {
+                categorize_crate_type(s)
+            } else {
+                None
+            }
+        });
+        base.extend(attr_types);
+        if base.is_empty() {
+            base.push(default_output_for_target(session));
+        } else {
+            base.sort();
+            base.dedup();
+        }
+    }
+
+    base.retain(|crate_type| {
+        if invalid_output_for_target(session, *crate_type) {
+            session.dcx().emit_warn(errors::UnsupportedCrateTypeForTarget {
+                crate_type: *crate_type,
+                target_triple: &session.opts.target_triple,
+            });
+            false
+        } else {
+            true
+        }
+    });
+
+    base
+}