Fix DCA for used struct/enum function parameters. (FuelLabs#2468)

This fixes DCA of struct/enum types that are used as function
parameters, but otherwise not instantiated in the module.

This is done by introducing a new graph edge between struct/enum
parameters and their respective struct/enum declarations.

Closes FuelLabs#2425.

Co-authored-by: Mohammad Fawaz <[email protected]>

sway-core/src/control_flow_analysis/dead_code_analysis.rs

@@ -577,14 +577,18 @@ fn connect_enum_declaration(
     graph: &mut ControlFlowGraph,
     entry_node: NodeIndex,
 ) {
+    graph
+        .namespace
+        .insert_enum(enum_decl.name.clone(), entry_node);
+
     // keep a mapping of each variant
     for variant in &enum_decl.variants {
         let variant_index = graph.add_node(ControlFlowGraphNode::from_enum_variant(
             variant,
             enum_decl.visibility != Visibility::Private,
         ));
 
-        graph.namespace.insert_enum(
+        graph.namespace.insert_enum_variant(
             enum_decl.name.clone(),
             entry_node,
             variant.name.clone(),
@@ -630,6 +634,40 @@ fn connect_typed_fn_decl(
     graph
         .namespace
         .insert_function(fn_decl.name.clone(), namespace_entry);
+
+    connect_fn_params_struct_enums(fn_decl, graph, entry_node)?;
+    Ok(())
+}
+
+// Searches for any structs or enums types referenced by the function
+// parameters from the passed function declaration and connects their
+// corresponding struct/enum declaration to the function entry node, thus
+// making sure they are considered used by the DCA pass.
+fn connect_fn_params_struct_enums(
+    fn_decl: &TypedFunctionDeclaration,
+    graph: &mut ControlFlowGraph,
+    fn_decl_entry_node: NodeIndex,
+) -> Result<(), CompileError> {
+    for fn_param in &fn_decl.parameters {
+        let ty = resolve_type(fn_param.type_id, &fn_param.type_span)?;
+        match ty {
+            TypeInfo::Enum { name, .. } => {
+                let ty_index = match graph.namespace.find_enum(&name) {
+                    Some(ix) => *ix,
+                    None => graph.add_node(format!("External enum  {}", name.as_str()).into()),
+                };
+                graph.add_edge(fn_decl_entry_node, ty_index, "".into());
+            }
+            TypeInfo::Struct { name, .. } => {
+                let ty_index = match graph.namespace.find_struct_decl(name.as_str()) {
+                    Some(ix) => *ix,
+                    None => graph.add_node(format!("External struct  {}", name.as_str()).into()),
+                };
+                graph.add_edge(fn_decl_entry_node, ty_index, "".into());
+            }
+            _ => {}
+        }
+    }
     Ok(())
 }
 

sway-core/src/control_flow_analysis/flow_graph/namespace.rs

@@ -55,7 +55,11 @@ impl ControlFlowNamespace {
     pub(crate) fn insert_constant(&mut self, const_name: Ident, declaration_node: NodeIndex) {
         self.const_namespace.insert(const_name, declaration_node);
     }
-    pub(crate) fn insert_enum(
+    pub(crate) fn insert_enum(&mut self, enum_name: Ident, enum_decl_index: NodeIndex) {
+        self.enum_namespace
+            .insert(enum_name, (enum_decl_index, HashMap::new()));
+    }
+    pub(crate) fn insert_enum_variant(
         &mut self,
         enum_name: Ident,
         enum_decl_index: NodeIndex,
@@ -77,6 +81,9 @@ impl ControlFlowNamespace {
             }
         }
     }
+    pub(crate) fn find_enum(&self, enum_name: &Ident) -> Option<&NodeIndex> {
+        self.enum_namespace.get(enum_name).map(|f| &f.0)
+    }
     pub(crate) fn find_enum_variant_index(
         &self,
         enum_name: &Ident,

sway-core/src/error.rs

@@ -417,7 +417,7 @@ impl fmt::Display for Warning {
                 "This trait implementation overrides another one that was previously defined."
             ),
             DeadDeclaration => write!(f, "This declaration is never used."),
-            DeadStructDeclaration => write!(f, "This struct is never instantiated."),
+            DeadStructDeclaration => write!(f, "This struct is never used."),
             DeadFunctionDeclaration => write!(f, "This function is never called."),
             UnreachableCode => write!(f, "This code is unreachable."),
             DeadEnumVariant { variant_name } => {

test/src/e2e_vm_tests/test_programs/should_pass/language/dca_constant_decl_expr/Forc.lock → test/src/e2e_vm_tests/test_programs/should_pass/dca/constant_decl_expr/Forc.lock

@@ -1,4 +1,4 @@
 [[package]]
-name = 'dca_constant_decl_expr'
+name = 'constant_decl_expr'
 source = 'root'
 dependencies = []

test/src/e2e_vm_tests/test_programs/should_pass/language/dca_constant_decl_expr/Forc.toml → test/src/e2e_vm_tests/test_programs/should_pass/dca/constant_decl_expr/Forc.toml

@@ -1,6 +1,6 @@
 [project]
 authors = ["Fuel Labs <[email protected]>"]
 license = "Apache-2.0"
-name = "dca_constant_decl_expr"
+name = "constant_decl_expr"
 entry = "main.sw"
 implicit-std = false

test/src/e2e_vm_tests/test_programs/should_pass/language/dca_constant_decl_expr/test.toml → test/src/e2e_vm_tests/test_programs/should_pass/dca/constant_decl_expr/test.toml

@@ -1,5 +1,4 @@
 category = "compile"
-validate_abi = true
 
 # not: const C1 = 66;
 # not: -------------- This declaration is never used.

test/src/e2e_vm_tests/test_programs/should_pass/dca/contract/abi_fn_params/Forc.lock

@@ -0,0 +1,4 @@
+[[package]]
+name = 'abi_fn_params'
+source = 'root'
+dependencies = []

test/src/e2e_vm_tests/test_programs/should_pass/dca/contract/abi_fn_params/Forc.toml

@@ -0,0 +1,6 @@
+[project]
+authors = ["Fuel Labs <[email protected]>"]
+license = "Apache-2.0"
+name = "abi_fn_params"
+entry = "main.sw"
+implicit-std = false

test/src/e2e_vm_tests/test_programs/should_pass/dca/contract/abi_fn_params/src/main.sw

@@ -0,0 +1,22 @@
+contract;
+
+struct S {
+}
+
+enum E {
+}
+
+abi MyContract {
+    fn get_struct(s: S) -> S;
+    fn get_enum(e: E) -> E;
+}
+
+impl MyContract for Contract {
+    fn get_struct(s: S) -> S {
+        s
+    }
+
+    fn get_enum(e: E) -> E {
+        e
+    }
+}

test/src/e2e_vm_tests/test_programs/should_pass/dca/contract/abi_fn_params/test.toml

@@ -0,0 +1,4 @@
+category = "compile"
+
+# not: $()This struct is never used.
+# not: $()This declaration is never used.

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/fn_params_free/Forc.lock

@@ -0,0 +1,4 @@
+[[package]]
+name = 'fn_params_free'
+source = 'root'
+dependencies = []

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/fn_params_free/Forc.toml

@@ -0,0 +1,6 @@
+[project]
+authors = ["Fuel Labs <[email protected]>"]
+license = "Apache-2.0"
+name = "fn_params_free"
+entry = "main.sw"
+implicit-std = false

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/fn_params_free/src/main.sw

@@ -0,0 +1,7 @@
+library foo;
+
+struct S {}
+
+pub fn free_fn(s: S) -> S {
+    s
+}

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/fn_params_free/test.toml

@@ -0,0 +1,4 @@
+category = "compile"
+
+# not: $()This struct is never used.
+# not: $()This declaration is never used.

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/fn_params_impl/Forc.lock

@@ -0,0 +1,4 @@
+[[package]]
+name = 'fn_params_impl'
+source = 'root'
+dependencies = []

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/fn_params_impl/Forc.toml

@@ -0,0 +1,6 @@
+[project]
+authors = ["Fuel Labs <[email protected]>"]
+license = "Apache-2.0"
+name = "fn_params_impl"
+entry = "main.sw"
+implicit-std = false

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/fn_params_impl/src/main.sw

@@ -0,0 +1,11 @@
+library foo;
+
+struct S {}
+
+pub struct F {}
+
+impl F {
+    pub fn free_fn(s: S) -> S {
+        s
+    }
+}

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/fn_params_impl/test.toml

@@ -0,0 +1,4 @@
+category = "compile"
+
+# not: $()This struct is never used.
+# not: $()This declaration is never used.

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/fn_params_trait/Forc.lock

@@ -0,0 +1,4 @@
+[[package]]
+name = 'fn_params_trait'
+source = 'root'
+dependencies = []

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/fn_params_trait/Forc.toml

@@ -0,0 +1,6 @@
+[project]
+authors = ["Fuel Labs <[email protected]>"]
+license = "Apache-2.0"
+name = "fn_params_trait"
+entry = "main.sw"
+implicit-std = false

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/fn_params_trait/src/main.sw

@@ -0,0 +1,15 @@
+library foo;
+
+struct S {}
+
+pub struct F {}
+
+trait T {
+    fn bar(t: S) -> S; // pub by default
+}
+
+impl T for F {
+    fn bar(s: S) -> S {
+        s
+    }
+}

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/fn_params_trait/test.toml

@@ -0,0 +1,4 @@
+category = "compile"
+
+# not: $()This struct is never used.
+# not: $()This declaration is never used.

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/unused_pub_free_fn/Forc.lock

@@ -0,0 +1,4 @@
+[[package]]
+name = 'unused_pub_free_fn'
+source = 'root'
+dependencies = []

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/unused_pub_free_fn/Forc.toml

@@ -0,0 +1,6 @@
+[project]
+authors = ["Fuel Labs <[email protected]>"]
+license = "Apache-2.0"
+name = "unused_pub_free_fn"
+entry = "main.sw"
+implicit-std = false

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/unused_pub_free_fn/src/main.sw

@@ -0,0 +1,3 @@
+library foo;
+
+pub fn free_fn() {}

test/src/e2e_vm_tests/test_programs/should_pass/dca/library/unused_pub_free_fn/test.toml

@@ -0,0 +1,4 @@
+category = "compile"
+
+# not: $()This function is never called.
+

test/src/e2e_vm_tests/test_programs/should_pass/dca/unused_free_fn/Forc.lock

@@ -0,0 +1,4 @@
+[[package]]
+name = 'unused_free_fn'
+source = 'root'
+dependencies = []

test/src/e2e_vm_tests/test_programs/should_pass/dca/unused_free_fn/Forc.toml

@@ -0,0 +1,6 @@
+[project]
+authors = ["Fuel Labs <[email protected]>"]
+license = "Apache-2.0"
+name = "unused_free_fn"
+entry = "main.sw"
+implicit-std = false

test/src/e2e_vm_tests/test_programs/should_pass/dca/unused_free_fn/src/main.sw

@@ -0,0 +1,5 @@
+script;
+
+fn free_fn() {}
+
+fn main() {}

test/src/e2e_vm_tests/test_programs/should_pass/dca/unused_free_fn/test.toml

@@ -0,0 +1,5 @@
+category = "compile"
+
+# check: $()fn free_fn() {}
+# nextln: $()This function is never called.
+

test/src/e2e_vm_tests/test_programs/should_pass/dca/unused_struct/Forc.lock

@@ -0,0 +1,4 @@
+[[package]]
+name = 'unused_struct'
+source = 'root'
+dependencies = []

test/src/e2e_vm_tests/test_programs/should_pass/dca/unused_struct/Forc.toml

@@ -0,0 +1,6 @@
+[project]
+authors = ["Fuel Labs <[email protected]>"]
+license = "Apache-2.0"
+name = "unused_struct"
+entry = "main.sw"
+implicit-std = false

test/src/e2e_vm_tests/test_programs/should_pass/dca/unused_struct/src/main.sw

@@ -0,0 +1,7 @@
+script;
+
+struct S {}
+
+fn main() {
+
+}

test/src/e2e_vm_tests/test_programs/should_pass/dca/unused_struct/test.toml

@@ -0,0 +1,5 @@
+category = "compile"
+
+# check: $()struct S {}
+# nextln: $()This struct is never used.
+