Validate retained effect parameter names

Author: olwang

src/analyzer.rs

@@ -1,3 +1,5 @@
+use std::collections::HashSet;
+
 use crate::checks;
 use crate::diagnostic::{Diagnostic, code};
 use crate::hir::{DuplicateSymbolKind, Hir, HirTypeKind};
@@ -136,6 +138,36 @@ impl Analyzer<'_> {
                     ));
                 }
             }
+
+            let param_names: HashSet<&str> = function
+                .params
+                .iter()
+                .map(|param| param.name.as_str())
+                .collect();
+            for effect in &function.effects {
+                let EffectDecl::Retains(param) = effect else {
+                    continue;
+                };
+                if !param_names.contains(param.as_str()) {
+                    self.diagnostics.push(
+                        Diagnostic::error(
+                            code::UNKNOWN_RETAINED_PARAMETER,
+                            format!(
+                                "`{}` declares `effects(retains({param}))`, but `{param}` is not a parameter.",
+                                function.name
+                            ),
+                            function.span.clone(),
+                            "unknown retained parameter",
+                        )
+                        .with_cause("Retention effects must name a parameter from the same function signature.")
+                        .with_fix(
+                            "fix_retains_parameter",
+                            "Rename the retained parameter or remove this retention effect.",
+                            "manual",
+                        ),
+                    );
+                }
+            }
         }
     }
 

src/diagnostic.rs

@@ -7,6 +7,7 @@ pub mod code {
     pub const UNKNOWN_EFFECT: &str = "RS0004";
     pub const DUPLICATE_DECLARATION: &str = "RS0005";
     pub const DUPLICATE_FILE_MODE: &str = "RS0006";
+    pub const UNKNOWN_RETAINED_PARAMETER: &str = "RS0007";
     pub const FILE_MODE_VIOLATION: &str = "RS0101";
     pub const UNNAMED_ARGUMENT: &str = "RS0201";
     pub const MISSING_DATA_EFFECT: &str = "RS0202";
@@ -224,6 +225,11 @@ static DIAGNOSTIC_EXPLANATIONS: &[DiagnosticExplanation] = &[
         title: "duplicate file mode",
         explanation: "Every RSScript source file must declare exactly one semantic mode. Multiple `mode:` declarations make local-capability review ambiguous.",
     },
+    DiagnosticExplanation {
+        code: code::UNKNOWN_RETAINED_PARAMETER,
+        title: "unknown retained parameter",
+        explanation: "`effects(retains(param))` must name a parameter declared by the function signature.",
+    },
     DiagnosticExplanation {
         code: code::FILE_MODE_VIOLATION,
         title: "file mode violation",

tests/fixtures/fail/unknown-retained-parameter.rss

@@ -0,0 +1,12 @@
+// expect: RS0007
+mode: managed
+
+struct Image {
+    pixels: Buffer
+}
+
+fn cache_put(image: read Image) -> Unit
+    effects(retains(value))
+{
+    return Unit
+}