statement inference: assignment

nac3core/src/lib.rs

@@ -7,6 +7,7 @@ extern crate rustpython_parser;
 
 pub mod expression_inference;
 pub mod inference_core;
+pub mod statement_inference;
 mod magic_methods;
 pub mod primitives;
 pub mod typedef;

nac3core/src/statement_inference.rs

@@ -0,0 +1,95 @@
+use crate::context::InferenceContext;
+use crate::expression_inference::infer_expr;
+use crate::inference_core::resolve_call;
+use crate::magic_methods::*;
+use crate::primitives::*;
+use crate::typedef::{Type, TypeEnum::*};
+use rustpython_parser::ast::*;
+
+fn get_target_type<'b: 'a, 'a>(
+    ctx: &mut InferenceContext<'a>,
+    target: &'b Expression,
+) -> Result<Type, String> {
+    match &target.node {
+        ExpressionType::Subscript { a, b } => {
+            let int32 = ctx.get_primitive(INT32_TYPE);
+            if infer_expr(ctx, &a)? == Some(int32) {
+                let b = get_target_type(ctx, &b)?;
+                if let ParametricType(LIST_TYPE, t) = b.as_ref() {
+                    Ok(t[0].clone())
+                } else {
+                    Err("subscript is only supported for list".to_string())
+                }
+            } else {
+                Err("subscript must be int32".to_string())
+            }
+        }
+        ExpressionType::Attribute { value, name } => {
+            let t = get_target_type(ctx, &value)?;
+            let base = t.get_base(ctx).ok_or_else(|| "no attributes".to_string())?;
+            Ok(base
+                .fields
+                .get(name.as_str())
+                .ok_or_else(|| "no such attribute")?
+                .clone())
+        }
+        ExpressionType::Identifier { name } => Ok(ctx.resolve(name.as_str())?),
+        _ => Err("not supported".to_string()),
+    }
+}
+
+fn check_stmt_binding<'b: 'a, 'a>(
+    ctx: &mut InferenceContext<'a>,
+    target: &'b Expression,
+    ty: Type,
+) -> Result<(), String> {
+    match &target.node {
+        ExpressionType::Identifier { name } => {
+            if name.as_str() == "_" {
+                Ok(())
+            } else {
+                match ctx.resolve(name.as_str()) {
+                    Ok(t) if t == ty => Ok(()),
+                    Err(_) => {
+                        ctx.assign(name.as_str(), ty).unwrap();
+                        Ok(())
+                    }
+                    _ => Err("conflicting type".into()),
+                }
+            }
+        }
+        ExpressionType::Tuple { elements } => {
+            if let ParametricType(TUPLE_TYPE, ls) = ty.as_ref() {
+                if ls.len() != elements.len() {
+                    return Err("incorrect pattern length".into());
+                }
+                for (x, y) in elements.iter().zip(ls.iter()) {
+                    check_stmt_binding(ctx, x, y.clone())?;
+                }
+                Ok(())
+            } else {
+                Err("pattern matching supports tuple only".into())
+            }
+        }
+        _ => {
+            let t = get_target_type(ctx, target)?;
+            if ty == t {
+                Ok(())
+            } else {
+                Err("type mismatch".into())
+            }
+        }
+    }
+}
+
+fn check_assign<'b: 'a, 'a>(
+    ctx: &mut InferenceContext<'a>,
+    targets: &'b [Expression],
+    value: &'b Expression,
+) -> Result<(), String> {
+    let ty = infer_expr(ctx, value)?.ok_or_else(|| "no value".to_string())?;
+    for t in targets.iter() {
+        check_stmt_binding(ctx, t, ty.clone())?;
+    }
+    Ok(())
+}