Infer datatype of another identifier

CHANGELOG.md

@@ -8,6 +8,7 @@
     codegen section can focus only in codegen, not in
     translation of thp->php.
 - Parse __more__ binary operators
+- Store tokens for the semantic analysis phase, to have actual error reporting
 - Parse more complex bindings
 - Watch mode
 - Improve error messages
@@ -24,8 +25,12 @@
 
 ## v0.0.12
 
+- [x] Infer datatype of an identifier
+- [ ] Infer datatype of a binary operatior
+- [ ] Infer datatype of unary operator
 - [ ] Infer datatype of a function call expression
 - [ ] Infer datatype of binary operators
+- [ ] Infer Int & Float as different types
 - [ ] Execute semantic analysis on the function's block
 - [ ] Write tests
 - [ ] Abstract the parsing of datatypes, such that in the future generics can be implemented in a single place

src/semantic/checks/binding.rs

@@ -28,7 +28,7 @@ impl SemanticCheck for Binding<'_> {
 
         // This gets the datatype of the assigned expression,
         // to compare it later with the declared datatype.
-        let expression_datatype = self.expression.get_type();
+        let expression_datatype = self.expression.get_type(scope)?;
 
         let datatype = match self.datatype {
             Some(t) => t.value.clone(),

src/semantic/symbol_table.rs

@@ -45,6 +45,11 @@ impl SymbolTable {
     pub fn test(&self, key: &String) -> bool {
         self.node.borrow_mut().test(key)
     }
+
+    /// Gets the datatype of a symbol, if it exists
+    pub fn get_type(&self, key: &String) -> Option<String> {
+        self.node.borrow_mut().get_type(key)
+    }
 }
 
 impl SymbolTableNode {
@@ -83,6 +88,27 @@ impl SymbolTableNode {
             None => false,
         }
     }
+
+    /// Returns the symbol's datatype
+    pub fn get_type(&mut self, key: &String) -> Option<String> {
+        // Try to get the type in the current scope
+        if let Some(entry) = self.scope.get(key) {
+            // TODO: Change to allow other types of datatypes: functions, classes, maps
+            return match entry {
+                SymbolEntry::Variable(t) => Some(t.clone()),
+                SymbolEntry::Function(_, _) => None,
+            }
+        }
+
+        // Try to get the type in the parent scope
+        match &self.parent {
+            Some(parent) => {
+                let mut parent = parent.as_ref().borrow_mut();
+                parent.get_type(key)
+            }
+            None => None,
+        }
+    }
 }
 
 impl SymbolEntry {

src/semantic/types/expression.rs

@@ -1,15 +1,34 @@
-use crate::syntax::ast::Expression;
+use crate::{
+    error_handling::{semantic_error::SemanticError, MistiError},
+    semantic::symbol_table::SymbolTable,
+    syntax::ast::Expression,
+};
 
 use super::Typed;
 
 impl Typed for Expression<'_> {
-    fn get_type(&self) -> String {
+    /// Attempts to get the datatype for an expression.
+    fn get_type(&self, scope: &SymbolTable) -> Result<String, MistiError> {
         match self {
             // TODO: Distinguish between Int & Float
-            Expression::Number(_) => "Int".into(),
-            Expression::String(_) => "String".into(),
-            Expression::Boolean(_) => "Bool".into(),
-            Expression::Identifier(_) => todo!(),
+            Expression::Number(_) => Ok("Int".into()),
+            Expression::String(_) => Ok("String".into()),
+            Expression::Boolean(_) => Ok("Bool".into()),
+            Expression::Identifier(identifier) => {
+                // Attempt to get the datatype of the identifier in the current scope
+                let datatype = match scope.get_type(identifier) {
+                    Some(x) => x,
+                    None => {
+                        return Err(MistiError::Semantic(SemanticError {
+                            error_start: 0,
+                            error_end: 1,
+                            reason: format!("The identifier {} does not exist.", identifier),
+                        }))
+                    }
+                };
+                
+                Ok(datatype)
+            }
             Expression::FunctionCall(_) => todo!(),
             Expression::UnaryOperator(_, _) => todo!(),
             Expression::BinaryOperator(_, _, _) => todo!(),

src/semantic/types/mod.rs

@@ -1,8 +1,12 @@
 // This crate provides an interface and implementations
 // for determining the datatypes of the language constructs.
 
+use crate::error_handling::MistiError;
+
+use super::symbol_table::SymbolTable;
+
 mod expression;
 
 pub trait Typed {
-    fn get_type(&self) -> String; 
+    fn get_type(&self, scope: &SymbolTable) -> Result<String, MistiError>;
 }