Implement unused variable detection

.gitignore

@@ -2,3 +2,5 @@
 Cargo.lock
 /target
 **/*.rs.bk
+.DS_Store
+.idea

src/sema/ast.rs

@@ -62,6 +62,7 @@ pub struct EventDecl {
     pub fields: Vec<Parameter>,
     pub signature: String,
     pub anonymous: bool,
+    pub used: bool,
 }
 
 impl fmt::Display for EventDecl {
@@ -284,6 +285,8 @@ pub struct Variable {
     pub visibility: pt::Visibility,
     pub constant: bool,
     pub initializer: Option<Expression>,
+    pub assigned: bool,
+    pub read: bool,
 }
 
 #[derive(Clone, PartialEq)]

src/sema/builtin.rs

@@ -467,7 +467,7 @@ pub fn resolve_call(
     args: &[pt::Expression],
     contract_no: Option<usize>,
     ns: &mut Namespace,
-    symtable: &Symtable,
+    symtable: &mut Symtable,
     is_constant: bool,
     diagnostics: &mut Vec<Diagnostic>,
 ) -> Result<Expression, ()> {
@@ -590,7 +590,7 @@ pub fn resolve_method_call(
     args: &[pt::Expression],
     contract_no: Option<usize>,
     ns: &mut Namespace,
-    symtable: &Symtable,
+    symtable: &mut Symtable,
     diagnostics: &mut Vec<Diagnostic>,
 ) -> Result<Expression, ()> {
     // The abi.* functions need special handling, others do not

src/sema/contracts.rs

@@ -13,6 +13,7 @@ use super::statements;
 use super::symtable::Symtable;
 use super::variables;
 use super::{ast, SOLANA_FIRST_OFFSET};
+use crate::sema::unused_variable::emit_warning_local_variable;
 use crate::{emit, Target};
 
 impl ast::Contract {
@@ -249,7 +250,7 @@ fn resolve_base_args(
                     .position(|e| e.contract_no == base_no)
                 {
                     if let Some(args) = &base.args {
-                        let symtable = Symtable::new();
+                        let mut symtable = Symtable::new();
 
                         // find constructor which matches this
                         if let Ok((Some(constructor_no), args)) = match_constructor_to_args(
@@ -259,7 +260,7 @@ fn resolve_base_args(
                             base_no,
                             *contract_no,
                             ns,
-                            &symtable,
+                            &mut symtable,
                             &mut diagnostics,
                         ) {
                             ns.contracts[*contract_no].bases[pos].constructor =
@@ -868,6 +869,12 @@ fn resolve_bodies(
             .is_err()
         {
             broken = true;
+        } else {
+            for (_, variable) in &ns.functions[function_no].symtable.vars {
+                if let Some(warning) = emit_warning_local_variable(&variable) {
+                    ns.diagnostics.push(*warning);
+                }
+            }
         }
     }