Implement string casts

compiler/tests/compile_errors.rs

@@ -27,6 +27,7 @@ use std::fs;
     case("unary_minus_on_bool.fe", "TypeError"),
     case("type_constructor_from_variable.fe", "NumericLiteralExpected"),
     case("needs_mem_copy.fe", "CannotMove"),
+    case("string_capacity_mismatch.fe", "StringCapacityMismatch"),
     case("numeric_capacity_mismatch/u8_neg.fe", "NumericCapacityMismatch"),
     case("numeric_capacity_mismatch/u8_pos.fe", "NumericCapacityMismatch"),
     case("numeric_capacity_mismatch/u16_neg.fe", "NumericCapacityMismatch"),

compiler/tests/evm_contracts.rs

@@ -756,6 +756,13 @@ fn strings() {
             Some(string_token("The quick brown fox jumps over the lazy dog")),
         );
 
+        harness.test_function(
+            &mut executor,
+            "return_casted_static_string",
+            vec![],
+            Some(string_token("foo")),
+        );
+
         harness.events_emitted(
             executor,
             vec![(
@@ -767,6 +774,7 @@ fn strings() {
                     string_token("string 3"),
                     address_token("1000000000000000000000000000000000000001"),
                     string_token("static string"),
+                    string_token("foo"),
                 ],
             )],
         );

compiler/tests/fixtures/compile_errors/string_capacity_mismatch.fe

@@ -0,0 +1,3 @@
+contract Foo:
+    pub def bar() -> string3:
+        return string3("too long")

compiler/tests/fixtures/strings.fe

@@ -6,12 +6,16 @@ contract Foo:
         s3: string100
         a: address
         s4: string13
+        s5: string100
 
     pub def __init__(s1: string42, a: address, s2: string26, u: u256, s3: string100):
-        emit MyEvent(s2, u, s1, s3, a, "static string")
+        emit MyEvent(s2, u, s1, s3, a, "static string", "foo")
 
     pub def bar(s1: string100, s2: string100) -> string100:
         return s2
 
-    pub def return_static_string() -> string43:
-        return "The quick brown fox jumps over the lazy dog"
+    pub def return_static_string() -> string50:
+        return string50("The quick brown fox jumps over the lazy dog")
+
+    pub def return_casted_static_string() -> string100:
+        return string100("foo")

newsfragments/201.feature.md

@@ -0,0 +1,7 @@
+Add support for string type casts
+
+Example:
+
+```
+val: string100 = string100("foo")
+```

semantics/src/errors.rs

@@ -11,6 +11,7 @@ pub enum ErrorKind {
     MissingReturn,
     NotSubscriptable,
     NumericCapacityMismatch,
+    StringCapacityMismatch,
     UndefinedValue,
     UnexpectedReturn,
     TypeError,
@@ -70,6 +71,14 @@ impl SemanticError {
         }
     }
 
+    /// Create a new error with kind `NumericCapacityMismatch`
+    pub fn string_capacity_mismatch() -> Self {
+        SemanticError {
+            kind: ErrorKind::StringCapacityMismatch,
+            context: vec![],
+        }
+    }
+
     /// Create a new error with kind `UndefinedValue`
     pub fn undefined_value() -> Self {
         SemanticError {

semantics/src/namespace/types.rs

@@ -157,6 +157,20 @@ pub struct FeString {
     pub max_size: usize,
 }
 
+impl TryFrom<&str> for FeString {
+    type Error = String;
+
+    fn try_from(value: &str) -> Result<Self, Self::Error> {
+        if !value.starts_with("string") {
+            return Err("Value must start with 'string'".to_string());
+        }
+
+        let max_size = value[6..].parse::<u32>().map_err(|err| err.to_string())? as usize;
+
+        Ok(FeString { max_size })
+    }
+}
+
 impl Integer {
     pub fn is_signed(&self) -> bool {
         matches!(
@@ -594,12 +608,9 @@ pub fn type_desc(defs: &HashMap<String, Type>, typ: &fe::TypeDesc) -> Result<Typ
         fe::TypeDesc::Base { base: "bool" } => Ok(Type::Base(Base::Bool)),
         fe::TypeDesc::Base { base: "bytes" } => Ok(Type::Base(Base::Byte)),
         fe::TypeDesc::Base { base: "address" } => Ok(Type::Base(Base::Address)),
-        fe::TypeDesc::Base { base } if &base[..6] == "string" => {
-            let max_size = base[6..]
-                .parse::<u32>()
-                .map_err(|_| SemanticError::type_error())? as usize;
-            Ok(Type::String(FeString { max_size }))
-        }
+        fe::TypeDesc::Base { base } if base.starts_with("string") => Ok(Type::String(
+            TryFrom::try_from(*base).map_err(|_| SemanticError::type_error())?,
+        )),
         fe::TypeDesc::Base { base } => {
             if let Some(typ) = defs.get(base.to_owned()) {
                 return Ok(typ.clone());

semantics/src/traversal/expressions.rs

@@ -4,6 +4,7 @@ use crate::namespace::scopes::{
     ContractFunctionDef,
     Shared,
 };
+use std::convert::TryFrom;
 
 use crate::builtins;
 use crate::namespace::operations;
@@ -27,6 +28,7 @@ use crate::{
     ExpressionAttributes,
     Location,
 };
+
 use fe_parser::ast as fe;
 use fe_parser::span::Spanned;
 use std::rc::Rc;
@@ -203,8 +205,9 @@ fn expr_str(
     exp: &Spanned<fe::Expr>,
 ) -> Result<ExpressionAttributes, SemanticError> {
     if let fe::Expr::Str(lines) = &exp.node {
-        let string_length = lines.iter().map(|val| val.len()).sum();
         let string_val = lines.join("");
+        let string_length = string_val.len();
+
         scope
             .borrow_mut()
             .contract_scope()
@@ -409,14 +412,23 @@ fn expr_call_type_constructor(
         return Err(SemanticError::wrong_number_of_params());
     }
 
-    let num = validate_is_numeric_literal(&args.node[0].node)?;
+    call_arg(Rc::clone(&scope), Rc::clone(&context), &args.node[0])?;
 
-    if !matches!(typ, Type::Base(Base::Address)) {
-        validate_literal_fits_type(&num, &typ)?;
-    }
+    match typ {
+        Type::String(ref fe_string) => {
+            validate_str_literal_fits_type(&args.node[0].node, &fe_string)?;
+            Ok(ExpressionAttributes::new(typ, Location::Memory))
+        }
+        _ => {
+            let num = validate_is_numeric_literal(&args.node[0].node)?;
 
-    call_arg(scope, context, &args.node[0])?;
-    Ok(ExpressionAttributes::new(typ, Location::Value))
+            if !matches!(typ, Type::Base(Base::Address)) {
+                validate_numeric_literal_fits_type(&num, &typ)?;
+            }
+
+            Ok(ExpressionAttributes::new(typ, Location::Value))
+        }
+    }
 }
 
 fn validate_is_numeric_literal(call_arg: &fe::CallArg) -> Result<String, SemanticError> {
@@ -431,7 +443,7 @@ fn validate_is_numeric_literal(call_arg: &fe::CallArg) -> Result<String, Semanti
     Err(SemanticError::numeric_literal_expected())
 }
 
-fn validate_literal_fits_type(num: &str, typ: &Type) -> Result<(), SemanticError> {
+fn validate_numeric_literal_fits_type(num: &str, typ: &Type) -> Result<(), SemanticError> {
     if let Type::Base(Base::Numeric(integer)) = typ {
         if integer.fits(num) {
             return Ok(());
@@ -443,6 +455,22 @@ fn validate_literal_fits_type(num: &str, typ: &Type) -> Result<(), SemanticError
     Err(SemanticError::type_error())
 }
 
+fn validate_str_literal_fits_type(
+    call_arg: &fe::CallArg,
+    typ: &FeString,
+) -> Result<(), SemanticError> {
+    if let fe::CallArg::Arg(fe::Expr::Str(lines)) = call_arg {
+        let string_length: usize = lines.join("").len();
+        if string_length > typ.max_size {
+            return Err(SemanticError::string_capacity_mismatch());
+        } else {
+            return Ok(());
+        }
+    }
+
+    Err(SemanticError::type_error())
+}
+
 fn expr_call_self_attribute(
     scope: Shared<BlockScope>,
     context: Shared<Context>,
@@ -568,6 +596,11 @@ fn expr_name_call_type(
         "i8" => Ok(CallType::TypeConstructor {
             typ: Type::Base(Base::Numeric(Integer::I8)),
         }),
+        value if value.starts_with("string") => Ok(CallType::TypeConstructor {
+            typ: Type::String(
+                TryFrom::try_from(value).map_err(|_| SemanticError::undefined_value())?,
+            ),
+        }),
         _ => Err(SemanticError::undefined_value()),
     }
 }