added return statement

boring/main.py

@@ -1,7 +1,7 @@
 import sys
 from typing import List
 from boring.parse import boring_parser, TreeToBoring, pretty_print
-from boring.type_checking import TypeChecker
+from boring.type_checking import TypeChecker, Context
 from boring import typedefs
 
 if __name__ == "__main__":
@@ -11,7 +11,7 @@ if __name__ == "__main__":
         result = TreeToBoring().transform(tree)
         # pretty_print(result)
         type_checker = TypeChecker()
-        while type_checker.with_module({}, typedefs.builtins, result):
+        while type_checker.with_module(Context({}, typedefs.builtins, None), result):
             print("loop")
         # type_checker.with_module({}, result)
         pretty_print(result)

boring/parse.py

@@ -26,6 +26,7 @@ def pretty_print(clas, indent=0):
 
 
 UNIT_TYPE = "()"
+NEVER_TYPE = "!"
 
 
 @dataclass
@@ -89,9 +90,15 @@ class VariableUsage:
     type: TypeUsage
 
 
+@dataclass
+class ReturnStatement:
+    source: "Expression"
+    type: TypeUsage
+
+
 @dataclass
 class Expression:
-    expression: Union[LiteralInt, LiteralFloat, FunctionCall, "Block", VariableUsage, Operation]
+    expression: Union[LiteralInt, LiteralFloat, FunctionCall, "Block", ReturnStatement, VariableUsage, Operation]
     type: TypeUsage
 
 
@@ -150,6 +157,8 @@ boring_grammar = r"""
 
     variable_usage : identifier
 
+    return_statement : "return" expression ";"
+
     expression : add_expression
                | sub_expression
                | factor
@@ -169,6 +178,7 @@ boring_grammar = r"""
                   | "let" identifier ":" type_usage "=" expression ";"
 
     statement : let_statement
+              | return_statement
               | expression
 
     block : "{" (statement)* "}"
@@ -238,6 +248,10 @@ class TreeToBoring(Transformer):
         (variable,) = variable
         return VariableUsage(name=variable, type=UnknownTypeUsage())
 
+    def return_statement(self, return_expression) -> ReturnStatement:
+        (return_expression,) = return_expression
+        return ReturnStatement(source=return_expression, type=DataTypeUsage(name=NEVER_TYPE))
+
     def function_call(self, call) -> FunctionCall:
         return FunctionCall(source=call[0], arguments=call[1:], type=UnknownTypeUsage())
 

boring/type_checking.py

@@ -9,15 +9,24 @@ Identified = Union[parse.LetStatement, parse.Function, parse.VariableDeclaration
 Environment = Dict[str, Identified]
 TypeEnvironment = Dict[str, typedefs.TypeDef]
 
+@dataclass
+class Context:
+    environment: Environment
+    type_environment: TypeEnvironment
+    current_function: Optional[parse.Function]
 
-def unify(type_env: TypeEnvironment, first, second) -> bool:
+    def copy(self):
-    result, changed = type_compare(type_env, first.type, second.type)
+        return Context(self.environment.copy(), self.type_environment.copy(), self.current_function)
+
+
+def unify(ctx: Context, first, second) -> bool:
+    result, changed = type_compare(ctx, first.type, second.type)
     first.type = result
     second.type = result
     return changed
 
 
-def type_compare(type_env: TypeEnvironment, first, second) -> (parse.TypeUsage, bool):
+def type_compare(ctx: Context, first, second) -> (parse.TypeUsage, bool):
     print(first, second)
     if isinstance(first, parse.UnknownTypeUsage):
         if not isinstance(second, parse.UnknownTypeUsage):
@@ -32,20 +41,20 @@ def type_compare(type_env: TypeEnvironment, first, second) -> (parse.TypeUsage,
                 second, parse.DataTypeUsage
             ):
                 assert second == first
-                assert first.name in type_env
+                assert first.name in ctx.type_environment
-                assert second.name in type_env
+                assert second.name in ctx.type_environment
                 return first, False
             elif isinstance(first, parse.FunctionTypeUsage) and isinstance(
                 second, parse.FunctionTypeUsage
             ):
                 return_type, changed = type_compare(
-                    type_env, first.return_type, second.return_type
+                    ctx, first.return_type, second.return_type
                 )
                 arguments = []
                 assert len(first.arguments) == len(second.arguments)
                 for first_arg, second_arg in zip(first.arguments, second.arguments):
                     argument_type, argument_changed = type_compare(
-                        type_env, first_arg, second_arg
+                        ctx, first_arg, second_arg
                     )
                     arguments.append(argument_type)
                     if argument_changed:
@@ -56,122 +65,157 @@ def type_compare(type_env: TypeEnvironment, first, second) -> (parse.TypeUsage,
 
 
 class TypeChecker:
-    def with_module(self, env: Environment, type_env: TypeEnvironment, module: parse.Module) -> bool:
+    def with_module(self, ctx: Context, module: parse.Module) -> bool:
         for function in module.functions:
-            env[function.name] = function
+            ctx.environment[function.name] = function
-        found = False
+        changed = False
         for function in module.functions:
-            if self.with_function(env, type_env, function):
+            if self.with_function(ctx, function):
-                found = True
+                changed = True
-        return found
+        return changed
 
-    def with_function(self, env: Environment, type_env: TypeEnvironment, function: parse.Function) -> bool:
+    def with_function(self, ctx: Context, function: parse.Function) -> bool:
-        function_env = env.copy()
+        function_ctx = ctx.copy()
+        function_ctx.current_function = function
         for argument in function.arguments:
-            function_env[argument.name] = argument
+            function_ctx.environment[argument.name] = argument
         assert isinstance(function.type, parse.FunctionTypeUsage)
 
-        type, changed = type_compare(type_env, function.block.type, function.type.return_type)
+        changed = self.with_block(function_ctx, function.block)
+
+        if not (isinstance(function.block.type, parse.DataTypeUsage) and function.block.type.name == parse.NEVER_TYPE):
+            type, compare_changed = type_compare(function_ctx, function.block.type, function.type.return_type)
             function.block.type = type
             function.type.return_type = type
-        if self.with_block(function_env, type_env, function.block):
+            if compare_changed is True:
                 changed = True
         return changed
 
     # Skip variable VariableDeclaration
 
-    def with_block(self, env: Environment, type_env: TypeEnvironment, block: parse.Block) -> bool:
+    def with_block(self, ctx: Context, block: parse.Block) -> bool:
-        block_env = env.copy()
+        block_ctx = ctx.copy()
         # if parent is void, must be statement
         # if parent is type, must be expression
         changed = False
+        for statement in block.statements:
+            if self.with_statement(block_ctx, statement):
+                changed = True
         final = block.statements[-1]
         if isinstance(final, parse.LetStatement):
             if isinstance(block.type, parse.UnknownTypeUsage):
-                found = True
+                changed = True
                 block.type = parse.DataTypeUsage(
-                    name=parse.Identifier(name=parse.UNIT_TYPE)
+                    name=parse.UNIT_TYPE
                 )
             else:
                 assert block.type == parse.DataTypeUsage(
-                    name=parse.Identifier(name=parse.UNIT_TYPE)
+                    name=parse.UNIT_TYPE
+                )
+        elif isinstance(final, parse.ReturnStatement):
+            if isinstance(block.type, parse.UnknownTypeUsage):
+                changed = True
+                block.type = parse.DataTypeUsage(
+                    name=parse.NEVER_TYPE
+                )
+            else:
+                assert block.type == parse.DataTypeUsage(
+                    name=parse.NEVER_TYPE
                 )
         elif isinstance(final, parse.Expression):
-            if unify(type_env, final, block):
+            if unify(block_ctx, final, block):
-                changed = True
-
-        for statement in block.statements:
-            if self.with_statement(block_env, type_env, statement):
                 changed = True
         return changed
 
-    def with_statement(self, env: Environment, type_env: TypeEnvironment, statement: parse.Statement) -> bool:
+    def with_statement(self, ctx: Context, statement: parse.Statement) -> bool:
+        if isinstance(statement, parse.ReturnStatement):
+            return self.with_return_statement(ctx, statement)
         if isinstance(statement, parse.LetStatement):
-            return self.with_let_statement(env, type_env, statement)
+            return self.with_let_statement(ctx, statement)
         elif isinstance(statement, parse.Expression):  # expression
-            return self.with_expression(env, type_env, statement)
+            return self.with_expression(ctx, statement)
         else:
             assert False
 
     def with_let_statement(
-        self, env: Environment, type_env: TypeEnvironment, let_statement: parse.LetStatement
+        self, ctx: Context, let_statement: parse.LetStatement
     ) -> bool:
-        found = False
+        changed = False
-        env[let_statement.variable_name] = let_statement
+        ctx.environment[let_statement.variable_name] = let_statement
-        changed = unify(type_env, let_statement, let_statement.expression)
+        if self.with_expression(ctx, let_statement.expression):
-        if self.with_expression(env, type_env, let_statement.expression):
+            changed = True
+        changed = unify(ctx, let_statement, let_statement.expression)
+        return changed
+
+    def with_return_statement(
+        self, ctx: Context, return_statement: parse.ReturnStatement
+    ) -> bool:
+        changed = self.with_expression(ctx, return_statement.source)
+
+        # Doesn't match on an unreachable return
+        if not (isinstance(return_statement.source.type, parse.DataTypeUsage) and return_statement.source.type.name == parse.NEVER_TYPE):
+            type, compare_changed = type_compare(ctx, return_statement.source.type, ctx.current_function.type.return_type)
+            return_statement.source.type = type
+            ctx.current_function.type.return_type = type
+            if compare_changed is True:
                 changed = True
         return changed
 
-    def with_expression(self, env: Environment, type_env: TypeEnvironment, expression: parse.Expression) -> bool:
+    def with_expression(self, ctx: Context, expression: parse.Expression) -> bool:
         subexpression = expression.expression
-        changed = unify(type_env, subexpression, expression)
+        changed = False
 
         if isinstance(subexpression, parse.LiteralInt):
-            if self.with_literal_int(env, type_env, subexpression):
+            changed = self.with_literal_int(ctx, subexpression)
+            if unify(ctx, subexpression, expression):
                 changed = True
             return changed
         if isinstance(subexpression, parse.LiteralFloat):
-            if self.with_literal_float(env, type_env, subexpression):
+            changed = self.with_literal_float(ctx, subexpression)
+            if unify(ctx, subexpression, expression):
                 changed = True
             return changed
         if isinstance(subexpression, parse.FunctionCall):
-            if self.with_function_call(env, type_env, subexpression):
+            changed = self.with_function_call(ctx, subexpression)
+            if unify(ctx, subexpression, expression):
                 changed = True
             return changed
         if isinstance(subexpression, parse.Block):
-            if self.with_block(env, type_env, subexpression):
+            changed = self.with_block(ctx, subexpression)
+            if unify(ctx, subexpression, expression):
                 changed = True
             return changed
         if isinstance(subexpression, parse.VariableUsage):
-            if self.with_variable_usage(env, type_env, subexpression):
+            changed = self.with_variable_usage(ctx, subexpression)
+            if unify(ctx, subexpression, expression):
                 changed = True
             return changed
         if isinstance(subexpression, parse.Operation):
-            if self.with_operation(env, type_env, subexpression):
+            changed = self.with_operation(ctx, subexpression)
+            if unify(ctx, subexpression, expression):
                 changed = True
             return changed
         assert False
 
     def with_variable_usage(
-        self, env: Environment, type_env: TypeEnvironment, variable_usage: parse.VariableUsage
+        self, ctx: Context, variable_usage: parse.VariableUsage
     ) -> bool:
-        return unify(type_env, variable_usage, env[variable_usage.name])
+        return unify(ctx, variable_usage, ctx.environment[variable_usage.name])
 
-    def with_operation(self, env: Environment, type_env: TypeEnvironment, operation: parse.Operation) -> bool:
+    def with_operation(self, ctx: Context, operation: parse.Operation) -> bool:
         changed = False
-        if unify(type_env, operation, operation.left):
+        if self.with_expression(ctx, operation.left):
             changed = True
-        if unify(type_env, operation, operation.right):
+        if self.with_expression(ctx, operation.right):
             changed = True
-        if self.with_expression(env, type_env, operation.left):
+        if unify(ctx, operation, operation.left):
             changed = True
-        if self.with_expression(env, type_env, operation.right):
+        if unify(ctx, operation, operation.right):
             changed = True
         return changed
 
     def with_function_call(
-        self, env: Environment, type_env: TypeEnvironment, function_call: parse.FunctionCall
+        self, ctx: Context, function_call: parse.FunctionCall
     ) -> bool:
         changed = False
         if isinstance(function_call.source.type, parse.UnknownTypeUsage):
@@ -180,14 +224,14 @@ class TypeChecker:
                 return_type=parse.UnknownTypeUsage(),
             )
             changed = True
-        if self.with_expression(env, type_env, function_call.source):
+        if self.with_expression(ctx, function_call.source):
             changed = True
         for argument in function_call.arguments:
-            if self.with_expression(env, type_env, argument):
+            if self.with_expression(ctx, argument):
                 changed = True
 
         return_type, return_changed = type_compare(
-            type_env, function_call.type, function_call.source.type.return_type
+            ctx, function_call.type, function_call.source.type.return_type
         )
         function_call.type = return_type
         function_call.source.type.return_type = return_type
@@ -198,7 +242,7 @@ class TypeChecker:
             function_call.arguments, function_call.source.type.arguments
         ):
             argument_out_type, argument_changed = type_compare(
-                type_env, argument.type, function_call.source.type.return_type
+                ctx, argument.type, function_call.source.type.return_type
             )
             argument.type = argument_out_type
             function_call.source.type.return_type = argument_out_type
@@ -206,13 +250,13 @@ class TypeChecker:
                 changed = True
         return changed
 
-    def with_literal_float(self, env: Environment, type_env: TypeEnvironment, literal_float: parse.LiteralFloat) -> bool:
+    def with_literal_float(self, ctx: Context, literal_float: parse.LiteralFloat) -> bool:
         floats = ["F32", "F64", "F128"]
         if not isinstance(literal_float.type, parse.UnknownTypeUsage):
             assert literal_float.type.name in floats, f"{literal_float.type}"
         return False
 
-    def with_literal_int(self, env: Environment, type_env: TypeEnvironment, literal_int: parse.LiteralInt) -> bool:
+    def with_literal_int(self, ctx: Context, literal_int: parse.LiteralInt) -> bool:
         ints = ["I8", "I16", "I32", "I64", "I128", "U8", "U16", "U32", "U64", "U128"]
         if not isinstance(literal_int.type, parse.UnknownTypeUsage):
             assert literal_int.type.name in ints, f"{literal_int.type}"

examples/math/main.bl

@@ -1,6 +1,6 @@
 // adds a and b, but also 4 for some reason
 fn add(a: I32, b: I32): I32 {
-    let foo = 4;
+    let foo = 4; // because I feel like it
     let test_float: F32 = {
       10.2
     };
@@ -11,6 +11,18 @@ fn subtract(a: I32, b: I32): I32 {
     a - b
 }
 
+fn return_type_test(a: F64): F64 {
+    return a * 2.0;
+}
+
+fn i_hate_this(a: F64): F64 {
+    return {
+        return {
+            return a;
+        };
+    };
+}
+
 fn main(): I32 {
     add(4, subtract(5, 2))
 }