From fa240b137df27cf6a938eb0432ef62ad7ba718e4 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Wed, 5 Jul 2023 21:45:09 +0100
Subject: Parse implicit return

---
 .../ast/untyped/UntypedFunctionStatementNode.java  |  2 +-
 .../compiler/ast/untyped/UntypedReturnNode.java    |  9 ++++++
 .../java/org/shedlang/compiler/parser/Parser.java  | 36 ++++++++++++++++------
 .../shedlang/compiler/typechecker/TypeChecker.java |  6 ++++
 4 files changed, 43 insertions(+), 10 deletions(-)
 create mode 100644 src/main/java/org/shedlang/compiler/ast/untyped/UntypedReturnNode.java

(limited to 'src/main/java')

diff --git a/src/main/java/org/shedlang/compiler/ast/untyped/UntypedFunctionStatementNode.java b/src/main/java/org/shedlang/compiler/ast/untyped/UntypedFunctionStatementNode.java
index 45d71235..6ecff062 100644
--- a/src/main/java/org/shedlang/compiler/ast/untyped/UntypedFunctionStatementNode.java
+++ b/src/main/java/org/shedlang/compiler/ast/untyped/UntypedFunctionStatementNode.java
@@ -1,4 +1,4 @@
 package org.shedlang.compiler.ast.untyped;
 
-public sealed interface UntypedFunctionStatementNode extends UntypedNode permits UntypedExpressionStatementNode, UntypedValNode {
+public sealed interface UntypedFunctionStatementNode extends UntypedNode permits UntypedExpressionStatementNode, UntypedReturnNode, UntypedValNode {
 }
diff --git a/src/main/java/org/shedlang/compiler/ast/untyped/UntypedReturnNode.java b/src/main/java/org/shedlang/compiler/ast/untyped/UntypedReturnNode.java
new file mode 100644
index 00000000..36230db8
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/ast/untyped/UntypedReturnNode.java
@@ -0,0 +1,9 @@
+package org.shedlang.compiler.ast.untyped;
+
+import org.shedlang.compiler.sources.Source;
+
+public record UntypedReturnNode(
+    UntypedExpressionNode expression,
+    Source source
+) implements UntypedFunctionStatementNode {
+}
diff --git a/src/main/java/org/shedlang/compiler/parser/Parser.java b/src/main/java/org/shedlang/compiler/parser/Parser.java
index b1794c6c..a2b7b09b 100644
--- a/src/main/java/org/shedlang/compiler/parser/Parser.java
+++ b/src/main/java/org/shedlang/compiler/parser/Parser.java
@@ -71,16 +71,40 @@ public class Parser {
         return new UntypedArgsNode(positional, named, argsSource);
     }
 
+    private static List<UntypedFunctionStatementNode> parseBlock(TokenIterator<TokenType> tokens) {
+        tokens.skip(TokenType.SYMBOL_BRACE_OPEN);
+
+        if (tokens.trySkip(TokenType.SYMBOL_BRACE_CLOSE)) {
+            return List.of();
+        }
+
+        var body = new ArrayList<UntypedFunctionStatementNode>();
+
+        while (true) {
+            var statement = parseFunctionStatement(tokens);
+
+            body.add(statement);
+
+            if (tokens.isNext(TokenType.SYMBOL_BRACE_CLOSE) || statement instanceof UntypedReturnNode) {
+                tokens.skip(TokenType.SYMBOL_BRACE_CLOSE);
+                return body;
+            }
+        }
+    }
+
     private static UntypedFunctionStatementNode parseExpressionStatement(TokenIterator<TokenType> tokens) {
         var start = tokens.position();
 
         var expression = parseTopLevelExpression(tokens);
-        tokens.skip(TokenType.SYMBOL_SEMICOLON);
+
+        var isReturn = !tokens.trySkip(TokenType.SYMBOL_SEMICOLON);
 
         var end = tokens.position();
         var source = start.to(end);
 
-        return new UntypedExpressionStatementNode(expression, source);
+        return isReturn
+            ? new UntypedReturnNode(expression, source)
+            : new UntypedExpressionStatementNode(expression, source);
     }
 
     private static UntypedNamespaceStatementNode parseFunctionDefinition(TokenIterator<TokenType> tokens) {
@@ -103,13 +127,7 @@ public class Parser {
         tokens.skip(TokenType.SYMBOL_THIN_ARROW);
         var returnType = parseTopLevelTypeLevelExpression(tokens);
 
-        tokens.skip(TokenType.SYMBOL_BRACE_OPEN);
-        var body = parseMany(
-            () -> tokens.isNext(TokenType.SYMBOL_BRACE_CLOSE),
-            () -> parseFunctionStatement(tokens),
-            () -> true
-        );
-        tokens.skip(TokenType.SYMBOL_BRACE_CLOSE);
+        var body = parseBlock(tokens);
 
         var end = tokens.position();
         var source = start.to(end);
diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
index 626f1f92..4f8d051b 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
@@ -71,6 +71,9 @@ public class TypeChecker {
             case UntypedExpressionStatementNode expressionStatement ->
                 List.of();
 
+            case UntypedReturnNode return_ ->
+                List.of();
+
             case UntypedValNode val ->
                 targetVariables(val.target());
         };
@@ -307,6 +310,9 @@ public class TypeChecker {
             case UntypedExpressionStatementNode expressionStatement ->
                 typeCheckExpressionStatement(expressionStatement, context);
 
+            case UntypedReturnNode return_ ->
+                throw new UnsupportedOperationException("TODO");
+
             case UntypedValNode val ->
                 typeCheckVal(val, context);
         };
-- 
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