add basic type checking of lambda expressions

langserver/java/anys.js

@@ -87,7 +87,15 @@ class MethodType {
  * eg. `() => null`
  */
 class LambdaType {
-
+    /**
+     * 
+     * @param {JavaType[]} param_types 
+     * @param {ResolvedValue} return_type 
+     */
+    constructor(param_types, return_type) {
+        this.param_types = param_types;
+        this.return_type = return_type;
+    }
 }
 
 /**

langserver/java/expression-resolver.js

@@ -5,7 +5,7 @@
  */
 const ParseProblem = require('./parsetypes/parse-problem');
 const { TypeVariable, JavaType, PrimitiveType, NullType, ArrayType, CEIType, WildcardType, TypeVariableType, InferredTypeArgument } = require('java-mti');
-const { AnyType, ArrayValueType, MultiValueType } = require('./anys');
+const { AnyType, ArrayValueType, LambdaType, MultiValueType } = require('./anys');
 const { ResolveInfo } = require('./body-types');
 const { NumberLiteral } = require('./expressiontypes/literals/Number');
 
@@ -41,6 +41,10 @@ function checkTypeAssignable(variable_type, value, tokens, problems) {
         checkArrayLiteral(variable_type, value, tokens, problems);
         return;
     }
+    if (value instanceof LambdaType) {
+        checkLambdaAssignable(variable_type, value, tokens, problems);
+        return;
+    }
     if (value instanceof JavaType) {
         if (!isTypeAssignable(variable_type, value)) {
             incompatibleTypesError(variable_type, value, tokens, problems);
@@ -61,6 +65,78 @@ function incompatibleTypesError(variable_type, value_type, tokens, problems) {
     problems.push(ParseProblem.Error(tokens(), `Incompatible types: Expression of type '${value_type.fullyDottedTypeName}' cannot be assigned to a variable of type '${variable_type.fullyDottedTypeName}'`));
 }
 
+/**
+ * 
+ * @param {JavaType} variable_type 
+ * @param {LambdaType} value 
+ * @param {() => Token|Token[]} tokens
+ * @param {ParseProblem[]} problems
+ */
+function checkLambdaAssignable(variable_type, value, tokens, problems) {
+    const res = isLambdaAssignable(variable_type, value);
+    if (res === true) {
+        return;
+    }
+    switch (res[0]) {
+        case 'non-interface':
+            problems.push(ParseProblem.Error(tokens(), `Incompatible types: Cannot assign lambda expression to type '${variable_type.fullyDottedTypeName}'`));
+            return;
+        case 'no-methods':
+            problems.push(ParseProblem.Error(tokens(), `Incompatible types: Interface '${variable_type.fullyDottedTypeName}' contains no abstract methods compatible with the specified lambda expression`));
+            return;
+        case 'param-count':
+            problems.push(ParseProblem.Error(tokens(), `Incompatible types: Interface method '${variable_type.methods[0].label}' and lambda expression have different parameter counts`));
+            return;
+        case 'bad-param':
+            problems.push(ParseProblem.Error(tokens(), `Incompatible types: Interface method '${variable_type.methods[0].label}' and lambda expression have different parameter types`));
+            return;
+    }
+}
+
+/**
+ * 
+ * @param {JavaType} variable_type 
+ * @param {LambdaType} value 
+ */
+function isLambdaAssignable(variable_type, value) {
+    if (!(variable_type instanceof CEIType) || variable_type.typeKind !== 'interface') {
+        return ['non-interface'];
+    }
+    // the functional interface must only contain one abstract method excluding public Object methods
+    // and ignoring type-compatible methods from superinterfaces.
+    // this is quite complicated to calculate, so for now, just check against the most common case: a simple interface type with
+    // a single abstract method
+    if (variable_type.supers.length > 1) {
+        return true;
+    }
+    if (variable_type.methods.length === 0) {
+        return ['no-methods']
+    }
+    if (variable_type.methods.length > 1) {
+        return true;
+    }
+    const intf_method = variable_type.methods[0];
+    const intf_params = intf_method.parameters;
+    if (intf_params.length !== value.param_types.length) {
+        return ['param-count'];
+    }
+
+    for (let i = 0; i < intf_params.length; i++) {
+        // explicit parameter types must match exactly
+        if (value.param_types[i] instanceof AnyType) {
+            continue;
+        }
+        if (intf_params[i].type instanceof AnyType) {
+            continue;
+        }
+        if (intf_params[i].type.typeSignature !== value.param_types[i].typeSignature) {
+            return ['bad-param']
+        }
+    }
+
+    return true;
+}
+
 /**
  * 
  * @param {JavaType} variable_type 
@@ -168,7 +244,7 @@ const valid_primitive_types = {
 /**
  * Returns true if a value of value_type is assignable to a variable of dest_type
  * @param {JavaType} dest_type 
- * @param {JavaType|NumberLiteral} value_type 
+ * @param {JavaType|NumberLiteral|LambdaType} value_type 
  */
 function isTypeAssignable(dest_type, value_type) {
 
@@ -176,6 +252,10 @@ function isTypeAssignable(dest_type, value_type) {
         return value_type.isCompatibleWith(dest_type);
     }
 
+    if (value_type instanceof LambdaType) {
+        return isLambdaAssignable(dest_type, value_type) === true;
+    }
+
     let is_assignable = false;
     if (dest_type.typeSignature === value_type.typeSignature) {
         // exact signature match

langserver/java/expressiontypes/LambdaExpression.js

@@ -4,12 +4,13 @@
  */
 const { Expression } = require("./Expression");
 const { Block } = require('../statementtypes/Block');
-const { LambdaType } = require('../anys');
+const { AnyType, LambdaType } = require('../anys');
+const { Local } = require('../body-types');
 
 class LambdaExpression extends Expression {
     /**
      *
-     * @param {*[]} params
+     * @param {(Local|ResolvedIdent)[]} params
      * @param {ResolvedIdent|Block} body
      */
     constructor(params, body) {
@@ -22,7 +23,21 @@ class LambdaExpression extends Expression {
      * @param {ResolveInfo} ri 
      */
     resolveExpression(ri) {
-        return new LambdaType();
+        let return_type;
+        if (this.body instanceof Block) {
+            // todo - search for return statements to work out what return value the lambda has
+            return_type = AnyType.Instance;
+        } else {
+            return_type = this.body.resolveExpression(ri);
+        }
+        const param_types = this.params.map(p => {
+            if (p instanceof Local) {
+                return p.type;
+            }
+            return AnyType.Instance;
+        })
+        return new LambdaType(param_types, return_type);
+
     }
 
     tokens() {

langserver/java/expressiontypes/MethodCallExpression.js

@@ -4,7 +4,7 @@
  * @typedef {import('../tokenizer').Token} Token
  */
 const { Expression } = require("./Expression");
-const { AnyType, AnyMethod, MethodType } = require('../anys');
+const { AnyType, AnyMethod, LambdaType, MethodType } = require('../anys');
 const { ArrayType, JavaType, Method,PrimitiveType, ReifiedConstructor, ReifiedMethod, Constructor } = require('java-mti');
 const { NumberLiteral } = require('./literals/Number');
 const { InstanceLiteral } = require('./literals/Instance')
@@ -68,11 +68,11 @@ class MethodCallExpression extends Expression {
 function resolveMethodCall(ri, methods, args, tokens) {
     const resolved_args = args.map(arg => arg.resolveExpression(ri));
 
-    // all the arguments must be typed expressions or number literals
-    /** @type {(JavaType|NumberLiteral)[]} */
+    // all the arguments must be typed expressions, number literals or lambdas
+    /** @type {(JavaType|NumberLiteral|LambdaType)[]} */
     const arg_types = [];
     resolved_args.forEach((a, idx) => {
-        if (a instanceof JavaType || a instanceof NumberLiteral) {
+        if (a instanceof JavaType || a instanceof NumberLiteral || a instanceof LambdaType) {
             arg_types.push(a);
             return;
         }
@@ -82,7 +82,11 @@ function resolveMethodCall(ri, methods, args, tokens) {
     });
 
     // reify any methods with type-variables
-    const arg_java_types = arg_types.map(a => a instanceof NumberLiteral ? a.type : a);
+    // - lambda expressions can't be used as type arguments so just pass them as void
+    const arg_java_types = arg_types.map(a => 
+        a instanceof NumberLiteral ? a.type 
+        : a instanceof LambdaType ? PrimitiveType.map.V
+        : a);
     const reified_methods = methods.map(m => {
             if (m.typeVariables.length) {
                 m = ReifiedMethod.build(m, arg_java_types);
@@ -142,11 +146,11 @@ function resolveMethodCall(ri, methods, args, tokens) {
 function resolveConstructorCall(ri, constructors, args, tokens) {
     const resolved_args = args.map(arg => arg.resolveExpression(ri));
 
-    // all the arguments must be typed expressions or number literals
-    /** @type {(JavaType|NumberLiteral)[]} */
+    // all the arguments must be typed expressions, number literals or lambdas
+    /** @type {(JavaType|NumberLiteral|LambdaType)[]} */
     const arg_types = [];
     resolved_args.forEach((a, idx) => {
-        if (a instanceof JavaType || a instanceof NumberLiteral) {
+        if (a instanceof JavaType || a instanceof NumberLiteral || a instanceof LambdaType) {
             arg_types.push(a);
             return;
         }
@@ -156,7 +160,11 @@ function resolveConstructorCall(ri, constructors, args, tokens) {
     });
 
     // reify any methods with type-variables
-    const arg_java_types = arg_types.map(a => a instanceof NumberLiteral ? a.type : a);
+    // - lambda expressions can't be used as type arguments so just pass them as void
+    const arg_java_types = arg_types.map(a => 
+        a instanceof NumberLiteral ? a.type 
+        : a instanceof LambdaType ? PrimitiveType.map.V
+        : a);
     const reifed_ctrs = constructors.map(c => {
             if (c.typeVariables.length) {
                 c = ReifiedConstructor.build(c, arg_java_types);
@@ -206,7 +214,7 @@ function resolveConstructorCall(ri, constructors, args, tokens) {
 /**
  * 
  * @param {Method|Constructor} m 
- * @param {(JavaType | NumberLiteral)[]} arg_types 
+ * @param {(JavaType | NumberLiteral | LambdaType)[]} arg_types 
  */
 function isCallCompatible(m, arg_types) {
     if (m instanceof AnyMethod) {