Initial implementation of generics for C#

13 files changed, 437 insertions, 36 deletions

diff --git a/src/main/java/org/zwobble/couscous/ast/LiteralNode.java b/src/main/java/org/zwobble/couscous/ast/LiteralNode.java
index bb38562..df2b87c 100644
--- a/src/main/java/org/zwobble/couscous/ast/LiteralNode.java
+++ b/src/main/java/org/zwobble/couscous/ast/LiteralNode.java
@@ -1,10 +1,13 @@
 package org.zwobble.couscous.ast;
 
+import org.zwobble.couscous.ast.types.ParameterizedType;
 import org.zwobble.couscous.ast.types.ScalarType;
+import org.zwobble.couscous.ast.types.Type;
 import org.zwobble.couscous.ast.visitors.ExpressionNodeMapper;
 import org.zwobble.couscous.ast.visitors.NodeTransformer;
 import org.zwobble.couscous.values.*;
 
+import static org.zwobble.couscous.util.ExtraLists.list;
 import static org.zwobble.couscous.values.PrimitiveValues.value;
 
 public class LiteralNode implements ExpressionNode {
@@ -27,22 +30,22 @@ public class LiteralNode implements ExpressionNode {
     }
 
     public static LiteralNode literal(ScalarType type) {
-        return new LiteralNode(value(type), ObjectValues.CLASS);
+        return new LiteralNode(value(type), new ParameterizedType(ObjectValues.CLASS, list(type)));
     }
     
-    public static LiteralNode of(PrimitiveValue value, ScalarType type) {
+    public static LiteralNode of(PrimitiveValue value, Type type) {
         return new LiteralNode(value, type);
     }
     
     private final PrimitiveValue value;
-    private final ScalarType type;
+    private final Type type;
 
-    private LiteralNode(PrimitiveValue value, ScalarType type) {
+    private LiteralNode(PrimitiveValue value, Type type) {
         this.value = value;
         this.type = type;
     }
     
-    public ScalarType getType() {
+    public Type getType() {
         return type;
     }
     
diff --git a/src/main/java/org/zwobble/couscous/ast/types/BoundTypeParameter.java b/src/main/java/org/zwobble/couscous/ast/types/BoundTypeParameter.java
new file mode 100644
index 0000000..abb8906
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/types/BoundTypeParameter.java
@@ -0,0 +1,55 @@
+package org.zwobble.couscous.ast.types;
+
+public class BoundTypeParameter implements Type {
+    public static BoundTypeParameter boundTypeParameter(TypeParameter parameter, Type value) {
+        return new BoundTypeParameter(parameter, value);
+    }
+
+    private final TypeParameter parameter;
+    private final Type value;
+
+    public BoundTypeParameter(TypeParameter parameter, Type value) {
+        this.parameter = parameter;
+        this.value = value;
+    }
+
+    public TypeParameter getParameter() {
+        return parameter;
+    }
+
+    public Type getValue() {
+        return value;
+    }
+
+    @Override
+    public <T> T accept(Visitor<T> visitor) {
+        return visitor.visit(this);
+    }
+
+    @Override
+    public String toString() {
+        return "BoundTypeParameter(" +
+            "parameter=" + parameter +
+            ", value=" + value +
+            ')';
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        BoundTypeParameter that = (BoundTypeParameter) o;
+
+        if (!parameter.equals(that.parameter)) return false;
+        return value.equals(that.value);
+
+    }
+
+    @Override
+    public int hashCode() {
+        int result = parameter.hashCode();
+        result = 31 * result + value.hashCode();
+        return result;
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/types/ParameterizedType.java b/src/main/java/org/zwobble/couscous/ast/types/ParameterizedType.java
new file mode 100644
index 0000000..a23fdc0
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/types/ParameterizedType.java
@@ -0,0 +1,57 @@
+package org.zwobble.couscous.ast.types;
+
+import java.util.List;
+
+public class ParameterizedType implements Type {
+    public static ParameterizedType parameterizedType(ScalarType rawType, List<Type> parameters) {
+        return new ParameterizedType(rawType, parameters);
+    }
+
+    private final ScalarType rawType;
+    private final List<Type> parameters;
+
+    public ParameterizedType(ScalarType rawType, List<Type> parameters) {
+        this.rawType = rawType;
+        this.parameters = parameters;
+    }
+
+    public ScalarType getRawType() {
+        return rawType;
+    }
+
+    public List<Type> getParameters() {
+        return parameters;
+    }
+
+    @Override
+    public <T> T accept(Visitor<T> visitor) {
+        return visitor.visit(this);
+    }
+
+    @Override
+    public String toString() {
+        return "ParameterizedType(" +
+            "rawType=" + rawType +
+            ", parameters=" + parameters +
+            ')';
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        ParameterizedType that = (ParameterizedType) o;
+
+        if (!rawType.equals(that.rawType)) return false;
+        return parameters.equals(that.parameters);
+
+    }
+
+    @Override
+    public int hashCode() {
+        int result = rawType.hashCode();
+        result = 31 * result + parameters.hashCode();
+        return result;
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/types/Type.java b/src/main/java/org/zwobble/couscous/ast/types/Type.java
index e936279..2a64341 100644
--- a/src/main/java/org/zwobble/couscous/ast/types/Type.java
+++ b/src/main/java/org/zwobble/couscous/ast/types/Type.java
@@ -5,5 +5,8 @@ public interface Type {
 
     interface Visitor<T> {
         T visit(ScalarType type);
+        T visit(TypeParameter parameter);
+        T visit(ParameterizedType type);
+        T visit(BoundTypeParameter type);
     }
 }
diff --git a/src/main/java/org/zwobble/couscous/ast/types/TypeParameter.java b/src/main/java/org/zwobble/couscous/ast/types/TypeParameter.java
new file mode 100644
index 0000000..0dee75e
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/types/TypeParameter.java
@@ -0,0 +1,51 @@
+package org.zwobble.couscous.ast.types;
+
+public class TypeParameter implements Type {
+    public static TypeParameter typeParameter(ScalarType declaringType, String name) {
+        return new TypeParameter(declaringType, name);
+    }
+
+    private final ScalarType declaringType;
+    private final String name;
+
+    public TypeParameter(ScalarType declaringType, String name) {
+        this.declaringType = declaringType;
+        this.name = name;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    @Override
+    public <T> T accept(Visitor<T> visitor) {
+        return visitor.visit(this);
+    }
+
+    @Override
+    public String toString() {
+        return "TypeParameter(" +
+            "declaringType=" + declaringType +
+            ", name=" + name +
+            ')';
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        TypeParameter that = (TypeParameter) o;
+
+        if (!declaringType.equals(that.declaringType)) return false;
+        return name.equals(that.name);
+
+    }
+
+    @Override
+    public int hashCode() {
+        int result = declaringType.hashCode();
+        result = 31 * result + name.hashCode();
+        return result;
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/types/Types.java b/src/main/java/org/zwobble/couscous/ast/types/Types.java
index c222c54..5fb079b 100644
--- a/src/main/java/org/zwobble/couscous/ast/types/Types.java
+++ b/src/main/java/org/zwobble/couscous/ast/types/Types.java
@@ -1,5 +1,7 @@
 package org.zwobble.couscous.ast.types;
 
+import org.zwobble.couscous.values.ObjectValues;
+
 public class Types {
     public static ScalarType erasure(Type type) {
         return type.accept(new Type.Visitor<ScalarType>() {
@@ -7,6 +9,21 @@ public class Types {
             public ScalarType visit(ScalarType type) {
                 return type;
             }
+
+            @Override
+            public ScalarType visit(TypeParameter parameter) {
+                return ObjectValues.OBJECT;
+            }
+
+            @Override
+            public ScalarType visit(ParameterizedType type) {
+                return type.getRawType();
+            }
+
+            @Override
+            public ScalarType visit(BoundTypeParameter type) {
+                return erasure(type.getParameter());
+            }
         });
     }
 }
diff --git a/src/main/java/org/zwobble/couscous/backends/Names.java b/src/main/java/org/zwobble/couscous/backends/Names.java
index 094de02..1e9600a 100644
--- a/src/main/java/org/zwobble/couscous/backends/Names.java
+++ b/src/main/java/org/zwobble/couscous/backends/Names.java
@@ -3,10 +3,9 @@ package org.zwobble.couscous.backends;
 import com.google.common.base.Joiner;
 import com.google.common.collect.Iterables;
 import org.zwobble.couscous.ast.MethodSignature;
-import org.zwobble.couscous.ast.types.Type;
+import org.zwobble.couscous.ast.types.*;
 
 import static com.google.common.collect.Iterables.transform;
-import static org.zwobble.couscous.ast.types.Types.erasure;
 import static org.zwobble.couscous.util.ExtraLists.list;
 
 public class Names {
@@ -18,6 +17,26 @@ public class Names {
     }
 
     private static String typeToString(Type argument) {
-        return erasure(argument).getQualifiedName().replace('.', '_');
+        return argument.accept(new Type.Visitor<String>() {
+            @Override
+            public String visit(ScalarType type) {
+                return type.getQualifiedName().replace('.', '_');
+            }
+
+            @Override
+            public String visit(TypeParameter parameter) {
+                return parameter.getName();
+            }
+
+            @Override
+            public String visit(ParameterizedType type) {
+                return typeToString(type.getRawType());
+            }
+
+            @Override
+            public String visit(BoundTypeParameter type) {
+                return typeToString(type.getParameter());
+            }
+        });
     }
 }
diff --git a/src/main/java/org/zwobble/couscous/backends/csharp/CsharpCodeGenerator.java b/src/main/java/org/zwobble/couscous/backends/csharp/CsharpCodeGenerator.java
index 8388421..469705b 100644
--- a/src/main/java/org/zwobble/couscous/backends/csharp/CsharpCodeGenerator.java
+++ b/src/main/java/org/zwobble/couscous/backends/csharp/CsharpCodeGenerator.java
@@ -2,8 +2,7 @@ package org.zwobble.couscous.backends.csharp;
 
 import com.google.common.collect.ImmutableMap;
 import org.zwobble.couscous.ast.*;
-import org.zwobble.couscous.ast.types.ScalarType;
-import org.zwobble.couscous.ast.types.Type;
+import org.zwobble.couscous.ast.types.*;
 import org.zwobble.couscous.ast.visitors.NodeTransformer;
 import org.zwobble.couscous.backends.Names;
 import org.zwobble.couscous.values.*;
@@ -13,6 +12,7 @@ import java.util.Optional;
 
 import static org.zwobble.couscous.ast.types.Types.erasure;
 import static org.zwobble.couscous.util.Casts.tryCast;
+import static org.zwobble.couscous.util.ExtraLists.eagerMap;
 
 public class CsharpCodeGenerator {
     private final static Map<ScalarType, ScalarType> PRIMITIVES = ImmutableMap.<ScalarType, ScalarType>builder()
@@ -44,11 +44,39 @@ public class CsharpCodeGenerator {
     }
 
     private Type transformType(Type type) {
-        if (PRIMITIVES.containsKey(type)) {
-            return PRIMITIVES.get(type);
-        } else {
-            return addPrefix(type, namespace);
-        }
+        return type.accept(new Type.Visitor<Type>() {
+            @Override
+            public Type visit(ScalarType type) {
+                if (PRIMITIVES.containsKey(type)) {
+                    return PRIMITIVES.get(type);
+                } else {
+                    return addPrefix(type, namespace);
+                }
+            }
+
+            @Override
+            public TypeParameter visit(TypeParameter parameter) {
+                return parameter;
+            }
+
+            @Override
+            public Type visit(ParameterizedType type) {
+                if (type.getRawType().equals(ObjectValues.CLASS)) {
+                    return ScalarType.of("System.Type");
+                } else {
+                    return new ParameterizedType(
+                        (ScalarType) transformType(type.getRawType()),
+                        eagerMap(type.getParameters(), parameter -> transformType(parameter)));
+                }
+            }
+
+            @Override
+            public Type visit(BoundTypeParameter type) {
+                return new BoundTypeParameter(
+                    visit(type.getParameter()),
+                    transformType(type.getValue()));
+            }
+        });
     }
 
     private String transformMethodName(MethodSignature signature) {
@@ -81,9 +109,28 @@ public class CsharpCodeGenerator {
     private Type addPrefix(Type type, String namespace) {
         return type.accept(new Type.Visitor<Type>() {
             @Override
-            public Type visit(ScalarType type) {
+            public ScalarType visit(ScalarType type) {
                 return ScalarType.of(namespace + "." + type.getQualifiedName());
             }
+
+            @Override
+            public TypeParameter visit(TypeParameter parameter) {
+                return parameter;
+            }
+
+            @Override
+            public Type visit(ParameterizedType type) {
+                return new ParameterizedType(
+                    visit(type.getRawType()),
+                    eagerMap(type.getParameters(), parameter -> addPrefix(parameter, namespace)));
+            }
+
+            @Override
+            public Type visit(BoundTypeParameter type) {
+                return new BoundTypeParameter(
+                    visit(type.getParameter()),
+                    addPrefix(type.getValue(), namespace));
+            }
         });
     }
 }
diff --git a/src/main/java/org/zwobble/couscous/backends/csharp/CsharpSerializer.java b/src/main/java/org/zwobble/couscous/backends/csharp/CsharpSerializer.java
index c898525..0d38a88 100644
--- a/src/main/java/org/zwobble/couscous/backends/csharp/CsharpSerializer.java
+++ b/src/main/java/org/zwobble/couscous/backends/csharp/CsharpSerializer.java
@@ -1,8 +1,7 @@
 package org.zwobble.couscous.backends.csharp;
 
 import org.zwobble.couscous.ast.*;
-import org.zwobble.couscous.ast.types.ScalarType;
-import org.zwobble.couscous.ast.types.Type;
+import org.zwobble.couscous.ast.types.*;
 import org.zwobble.couscous.ast.visitors.NodeVisitor;
 import org.zwobble.couscous.backends.SourceCodeWriter;
 import org.zwobble.couscous.util.Action;
@@ -422,6 +421,34 @@ public class CsharpSerializer implements NodeVisitor {
                 writer.writeIdentifier(typeReference(type));
                 return null;
             }
+
+            @Override
+            public Void visit(TypeParameter parameter) {
+                writer.writeIdentifier(parameter.getName());
+                return null;
+            }
+
+            @Override
+            public Void visit(ParameterizedType type) {
+                writer.writeIdentifier(typeReference(type.getRawType()));
+                writer.writeSymbol("<");
+                writer.writeWithSeparator(
+                    type.getParameters(),
+                    parameter -> writeTypeReference(parameter),
+                    () -> {
+                        writer.writeSymbol(",");
+                        writer.writeSpace();
+                    }
+                );
+                writer.writeSymbol(">");
+                return null;
+            }
+
+            @Override
+            public Void visit(BoundTypeParameter type) {
+                writeTypeReference(type.getValue());
+                return null;
+            }
         });
     }
 
diff --git a/src/main/java/org/zwobble/couscous/frontends/java/JavaExpressionReader.java b/src/main/java/org/zwobble/couscous/frontends/java/JavaExpressionReader.java
index 98f2686..72766b3 100644
--- a/src/main/java/org/zwobble/couscous/frontends/java/JavaExpressionReader.java
+++ b/src/main/java/org/zwobble/couscous/frontends/java/JavaExpressionReader.java
@@ -184,7 +184,8 @@ public class JavaExpressionReader {
         List<ExpressionNode> arguments = readArguments(
             expression.resolveMethodBinding(),
             expression.arguments());
-        final Type type = typeOf(expression);
+        MethodSignature signature = JavaReader.signature(expression.resolveMethodBinding());
+        final Type type = signature.getReturnType();
 
         IMethodBinding methodBinding = expression.resolveMethodBinding();
         Type receiverType = typeOf(methodBinding.getDeclaringClass());
diff --git a/src/main/java/org/zwobble/couscous/frontends/java/JavaReader.java b/src/main/java/org/zwobble/couscous/frontends/java/JavaReader.java
index 950e678..382c592 100644
--- a/src/main/java/org/zwobble/couscous/frontends/java/JavaReader.java
+++ b/src/main/java/org/zwobble/couscous/frontends/java/JavaReader.java
@@ -1,6 +1,7 @@
 package org.zwobble.couscous.frontends.java;
 
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Iterables;
 import com.google.common.collect.Maps;
 import org.eclipse.jdt.core.compiler.IProblem;
 import org.eclipse.jdt.core.dom.*;
@@ -8,8 +9,10 @@ import org.zwobble.couscous.ast.*;
 import org.zwobble.couscous.ast.sugar.AnonymousClass;
 import org.zwobble.couscous.ast.sugar.Lambda;
 import org.zwobble.couscous.ast.sugar.TypeDeclarationBody;
+import org.zwobble.couscous.ast.types.BoundTypeParameter;
 import org.zwobble.couscous.ast.types.ScalarType;
 import org.zwobble.couscous.ast.types.Type;
+import org.zwobble.couscous.ast.types.TypeParameter;
 import org.zwobble.couscous.ast.visitors.NodeTransformer;
 import org.zwobble.couscous.util.ExtraLists;
 
@@ -17,6 +20,7 @@ import java.io.IOException;
 import java.nio.file.Path;
 import java.util.*;
 import java.util.function.Function;
+import java.util.stream.Collectors;
 
 import static com.google.common.collect.Iterables.concat;
 import static com.google.common.collect.Iterables.*;
@@ -29,8 +33,10 @@ import static org.zwobble.couscous.ast.FieldAccessNode.fieldAccess;
 import static org.zwobble.couscous.ast.FieldDeclarationNode.field;
 import static org.zwobble.couscous.ast.FormalTypeParameterNode.formalTypeParameter;
 import static org.zwobble.couscous.ast.InstanceReceiver.instanceReceiver;
+import static org.zwobble.couscous.ast.ReturnNode.returns;
 import static org.zwobble.couscous.ast.StaticReceiver.staticReceiver;
 import static org.zwobble.couscous.ast.ThisReferenceNode.thisReference;
+import static org.zwobble.couscous.ast.TypeCoercionNode.typeCoercion;
 import static org.zwobble.couscous.ast.VariableReferenceNode.reference;
 import static org.zwobble.couscous.ast.types.Types.erasure;
 import static org.zwobble.couscous.frontends.java.FreeVariables.findFreeVariables;
@@ -128,10 +134,14 @@ public class JavaReader {
         ScalarType name = generateAnonymousName(expression);
         Scope scope = outerScope.enterClass(name);
         IMethodBinding functionalInterfaceMethod = expression.resolveTypeBinding().getFunctionalInterfaceMethod();
-        return generateClosure(scope, name, toAnonymousClass(functionalInterfaceMethod, lambda.apply(scope)));
+        return generateClosure(scope, name, toAnonymousClass(scope, name, functionalInterfaceMethod, lambda.apply(scope)));
     }
 
-    private AnonymousClass toAnonymousClass(IMethodBinding functionalInterfaceMethod, Lambda lambda) {
+    private AnonymousClass toAnonymousClass(Scope scope, ScalarType name, IMethodBinding functionalInterfaceMethod, Lambda lambda) {
+        // TODO: does this need type coercion adding? Since the body is straight from the lambda, but the type signature is from the interface method
+        // TODO: can generate override methods by using a placeholder this reference for, well, this references.
+        // They can be replaced once the anonymous class is turned into a real class.
+        // Or perhaps we should just do the conversion directly? Since we (in practice) already know the real class name.
         MethodNode method = MethodNode.method(
             emptyList(),
             false,
@@ -140,10 +150,12 @@ public class JavaReader {
             typeOf(functionalInterfaceMethod.getReturnType()),
             Optional.of(lambda.getBody()));
 
+        Iterable<MethodNode> overrides = generateOverrideMethods(name, functionalInterfaceMethod, scope, method);
+
         return new AnonymousClass(
             superTypesAndSelf(functionalInterfaceMethod.getDeclaringClass()),
             list(),
-            list(method));
+            ExtraLists.cons(method, overrides));
     }
 
     private List<StatementNode> replaceCaptureReferences(
@@ -305,7 +317,7 @@ public class JavaReader {
 
         for (Object declaration : bodyDeclarations) {
             tryCast(MethodDeclaration.class, declaration)
-                .ifPresent(method -> readMethod(body, scope, method));
+                .ifPresent(method -> readMethod(body, scope, type, method));
 
             tryCast(Initializer.class, declaration)
                 .ifPresent(initializer -> body.addInitializer(
@@ -356,8 +368,9 @@ public class JavaReader {
 
     }
 
-    private void readMethod(TypeDeclarationBody.Builder builder, Scope outerScope, MethodDeclaration method) {
-        Scope scope = outerScope.enterMethod(method.getName().getIdentifier());
+    private void readMethod(TypeDeclarationBody.Builder builder, Scope outerScope, ScalarType type, MethodDeclaration method) {
+        String methodName = method.getName().getIdentifier();
+        Scope scope = outerScope.enterMethod(methodName);
 
         List<FormalArgumentNode> formalArguments = readFormalArguments(scope, method);
         List<AnnotationNode> annotations = readAnnotations(method);
@@ -370,16 +383,89 @@ public class JavaReader {
                 formalArguments,
                 body.get()));
         } else {
-            builder.addMethod(MethodNode.method(
+            boolean isStatic = Modifier.isStatic(method.getModifiers());
+            MethodNode methodNode = MethodNode.method(
                 annotations,
-                Modifier.isStatic(method.getModifiers()),
-                method.getName().getIdentifier(),
+                isStatic,
+                methodName,
                 formalArguments,
                 returnType.get(),
-                body));
+                body);
+            builder.addMethod(methodNode);
+
+            Iterable<MethodNode> overrideMethods = generateOverrideMethods(type, method.resolveBinding(), scope, methodNode);
+
+            for (MethodNode overrideMethod : overrideMethods) {
+                builder.addMethod(overrideMethod);
+            }
         }
     }
 
+    private Iterable<MethodNode> generateOverrideMethods(ScalarType type, IMethodBinding method, Scope scope, MethodNode methodNode) {
+        return transform(
+            filter(
+                overrides(method),
+                override -> !override.equals(methodNode.signature())),
+            override -> {
+                List<FormalArgumentNode> arguments = eagerMap(override.getArguments(), argument -> scope.formalArgument("arg", argument));
+                return MethodNode.method(
+                    methodNode.getAnnotations(),
+                    methodNode.isStatic(),
+                    methodNode.getName(),
+                    arguments,
+                    override.getReturnType(),
+                    Optional.of(list(
+                        returns(typeCoercion(
+                            MethodCallNode.methodCall(
+                                thisReference(type),
+                                methodNode.getName(),
+                                eagerMap(arguments, argument -> reference(argument)),
+                                methodNode.getReturnType()),
+                            override.getReturnType()))
+                    )));
+            });
+    }
+
+    private Iterable<MethodSignature> overrides(IMethodBinding methodBinding) {
+        ITypeBinding declaringClass = methodBinding.getDeclaringClass();
+
+        // TODO: remove duplication with JavaTypes
+        // TODO: consider superclass
+        return ExtraLists.concat(list(declaringClass), asList(declaringClass.getInterfaces()))
+            .stream()
+            .flatMap(type -> asList(type.getDeclaredMethods()).stream().filter(superMethod -> methodBinding.overrides(superMethod)))
+            .map(JavaReader::signature)
+            .collect(Collectors.toList());
+    }
+
+    // TODO: move this elsewhere
+    static MethodSignature signature(IMethodBinding method) {
+        ITypeBinding declaringClass = method.getDeclaringClass();
+        ITypeBinding erasedDeclaringClass = declaringClass.getErasure();
+
+        List<Type> argumentTypes = eagerMap(asList(method.getParameterTypes()), JavaTypes::typeOf);
+        Type returnType = typeOf(method.getReturnType());
+
+        if (declaringClass.isEqualTo(erasedDeclaringClass)) {
+            return new MethodSignature(method.getName(), argumentTypes, returnType);
+        } else {
+            IMethodBinding[] erasedMethods = erasedDeclaringClass.getDeclaredMethods();
+            IMethodBinding erasedMethod = Iterables.getOnlyElement(Iterables.filter(
+                asList(erasedMethods),
+                m -> m.isSubsignature(method)));
+            return new MethodSignature(
+                method.getName(),
+                eagerMap(
+                    argumentTypes,
+                    asList(erasedMethod.getParameterTypes()),
+                    (argumentType, erasedParameterType) -> new BoundTypeParameter((TypeParameter) typeOf(erasedParameterType), argumentType)),
+                new BoundTypeParameter(
+                    (TypeParameter) typeOf(erasedMethod.getReturnType()),
+                    returnType));
+        }
+    }
+
+
     private List<AnnotationNode> readAnnotations(MethodDeclaration method) {
         return eagerMap(asList(method.resolveBinding().getAnnotations()), this::readAnnotation);
     }
diff --git a/src/main/java/org/zwobble/couscous/frontends/java/JavaTypes.java b/src/main/java/org/zwobble/couscous/frontends/java/JavaTypes.java
index fd59e8c..f0060a2 100644
--- a/src/main/java/org/zwobble/couscous/frontends/java/JavaTypes.java
+++ b/src/main/java/org/zwobble/couscous/frontends/java/JavaTypes.java
@@ -2,16 +2,20 @@ package org.zwobble.couscous.frontends.java;
 
 import com.google.common.collect.ImmutableSet;
 import org.eclipse.jdt.core.dom.*;
+import org.zwobble.couscous.ast.types.ParameterizedType;
 import org.zwobble.couscous.ast.types.ScalarType;
 import org.zwobble.couscous.ast.types.Type;
-import org.zwobble.couscous.ast.types.Types;
+import org.zwobble.couscous.ast.types.TypeParameter;
 import org.zwobble.couscous.values.ObjectValues;
 
+import java.util.List;
 import java.util.Optional;
 import java.util.Set;
 
 import static com.google.common.collect.Iterables.transform;
 import static java.util.Arrays.asList;
+import static org.zwobble.couscous.ast.types.Types.erasure;
+import static org.zwobble.couscous.util.ExtraLists.eagerMap;
 
 class JavaTypes {
     static Type typeOf(Expression expression) {
@@ -29,9 +33,19 @@ class JavaTypes {
     static Type typeOf(ITypeBinding typeBinding) {
         ITypeBinding outerClass = typeBinding.getDeclaringClass();
         if (outerClass == null) {
-            return ScalarType.of(typeBinding.getErasure().getQualifiedName());
+            ScalarType rawType = ScalarType.of(typeBinding.getErasure().getQualifiedName());
+            if (typeBinding.isParameterizedType()) {
+                List<Type> typeParameters = eagerMap(
+                    asList(typeBinding.getTypeArguments()),
+                    JavaTypes::typeOf);
+                return new ParameterizedType(rawType, typeParameters);
+            } else {
+                return rawType;
+            }
+        } else if (typeBinding.isTypeVariable()) {
+            return new TypeParameter(erasure(typeOf(outerClass)), typeBinding.getName());
         } else {
-            return ScalarType.of(Types.erasure(typeOf(outerClass)).getQualifiedName() + "__" + typeBinding.getName());
+            return ScalarType.of(erasure(typeOf(outerClass)).getQualifiedName() + "__" + typeBinding.getName());
         }
     }
 
diff --git a/src/main/java/org/zwobble/couscous/util/ExtraLists.java b/src/main/java/org/zwobble/couscous/util/ExtraLists.java
index ce9230a..8485b02 100644
--- a/src/main/java/org/zwobble/couscous/util/ExtraLists.java
+++ b/src/main/java/org/zwobble/couscous/util/ExtraLists.java
@@ -1,8 +1,11 @@
 package org.zwobble.couscous.util;
 
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Iterables;
 
+import java.util.Iterator;
 import java.util.List;
+import java.util.function.BiFunction;
 import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
@@ -26,16 +29,16 @@ public class ExtraLists {
         return ImmutableList.of(value1, value2, value3);
     }
 
-    public static <T> List<T> cons(T value, List<T> list) {
-        return Stream.concat(Stream.of(value), list.stream()).collect(Collectors.toList());
+    public static <T> List<T> cons(T value, Iterable<T> list) {
+        return concat(list(value), list);
     }
 
     public static <T> List<T> append(List<T> list, T value) {
         return Stream.concat(list.stream(), Stream.of(value)).collect(Collectors.toList());
     }
 
-    public static <T> List<T> concat(List<? extends T> first, List<? extends T> second) {
-        return Stream.concat(first.stream(), second.stream()).collect(Collectors.toList());
+    public static <T> List<T> concat(Iterable<? extends T> first, Iterable<? extends T> second) {
+        return ImmutableList.copyOf(Iterables.concat(first, second));
     }
 
     public static <T> List<T> concat(List<? extends T> first, List<? extends T> second, List<? extends T> third) {
@@ -82,6 +85,24 @@ public class ExtraLists {
             .collect(Collectors.toList());
     }
 
+    public static <T1, T2, R> List<R> eagerMap(
+        Iterable<T1> iterable1,
+        Iterable<T2> iterable2,
+        BiFunction<T1, T2, R> function)
+    {
+        // TODO: error handling when iterables are different lengths
+        Iterator<T1> iterator1 = iterable1.iterator();
+        Iterator<T2> iterator2 = iterable2.iterator();
+
+        ImmutableList.Builder<R> result = ImmutableList.builder();
+
+        while (iterator1.hasNext()) {
+            result.add(function.apply(iterator1.next(), iterator2.next()));
+        }
+
+        return result.build();
+    }
+
     public static <T, R> List<R> eagerFlatMap(
         Iterable<T> iterable,
         Function<T, Iterable<R>> function) {