Parse function expressions

1 files changed, 246 insertions, 0 deletions

diff --git a/src/test/java/org/shedlang/compiler/parser/ParserFunctionExpressionTests.java b/src/test/java/org/shedlang/compiler/parser/ParserFunctionExpressionTests.java
new file mode 100644
index 00000000..d86776be
--- /dev/null
+++ b/src/test/java/org/shedlang/compiler/parser/ParserFunctionExpressionTests.java
@@ -0,0 +1,246 @@
+package org.shedlang.compiler.parser;
+
+import org.junit.jupiter.api.Test;
+import org.shedlang.compiler.parser.errors.PositionalParamAfterNamedParamError;
+import org.shedlang.compiler.tokeniser.UnexpectedTokenException;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.shedlang.compiler.ast.untyped.UntypedNodeMatchers.*;
+import static org.shedlang.compiler.parser.ParserTesting.parseString;
+import static org.zwobble.precisely.AssertThat.assertThat;
+import static org.zwobble.precisely.Matchers.*;
+
+public class ParserFunctionExpressionTests {
+    @Test
+    public void canParseMinimalFunction() {
+        var source = """
+            fn () -> Unit {
+            }""";
+
+        var node = parseString(source, Parser::parseTopLevelExpression);
+
+        assertThat(
+            node,
+            isUntypedFunctionExpressionNode()
+                .withParams(isUntypedParamsNode(isSequence(), isSequence()))
+                .withEffect(isOptionalEmpty())
+                .withReturnType(isUntypedTypeLevelReferenceNode("Unit"))
+                .withBody(isUntypedBlockNode(isSequence()))
+        );
+    }
+
+    @Test
+    public void canParseFunctionWithSinglePositionalParam() {
+        var source = """
+            fn (a: Int) -> Unit {
+            }""";
+
+        var node = parseString(source, Parser::parseTopLevelExpression);
+
+        assertThat(
+            node,
+            isUntypedFunctionExpressionNode()
+                .withParams(isUntypedParamsNode(
+                    isSequence(
+                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
+                    ),
+                    isSequence()
+                ))
+        );
+    }
+
+    @Test
+    public void canParseFunctionWithManyPositionalParams() {
+        var source = """
+            fn (a: Int, b: String, c: Bool) -> Unit {
+            }""";
+
+        var node = parseString(source, Parser::parseTopLevelExpression);
+
+        assertThat(
+            node,
+            isUntypedFunctionExpressionNode()
+                .withParams(isUntypedParamsNode(
+                    isSequence(
+                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int")),
+                        isUntypedParamNode("b", isUntypedTypeLevelReferenceNode("String")),
+                        isUntypedParamNode("c", isUntypedTypeLevelReferenceNode("Bool"))
+                    ),
+                    isSequence()
+                ))
+        );
+    }
+
+    @Test
+    public void canParseFunctionWithSingleNamedParam() {
+        var source = """
+            fn (.a: Int) -> Unit {
+            }""";
+
+        var node = parseString(source, Parser::parseTopLevelExpression);
+
+        assertThat(
+            node,
+            isUntypedFunctionExpressionNode()
+                .withParams(isUntypedParamsNode(
+                    isSequence(),
+                    isSequence(
+                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
+                    )
+                ))
+        );
+    }
+
+    @Test
+    public void canParseFunctionWithManyNamedParams() {
+        var source = """
+            fn (.a: Int, .b: String, .c: Bool) -> Unit {
+            }""";
+
+        var node = parseString(source, Parser::parseTopLevelExpression);
+
+        assertThat(
+            node,
+            isUntypedFunctionExpressionNode()
+                .withParams(isUntypedParamsNode(
+                    isSequence(),
+                    isSequence(
+                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int")),
+                        isUntypedParamNode("b", isUntypedTypeLevelReferenceNode("String")),
+                        isUntypedParamNode("c", isUntypedTypeLevelReferenceNode("Bool"))
+                    )
+                ))
+        );
+    }
+
+    @Test
+    public void canParseNamedParamAfterPositionalParam() {
+        var source = """
+            fn (a: Int, .b: String) -> Unit {
+            }""";
+
+        var node = parseString(source, Parser::parseTopLevelExpression);
+
+        assertThat(
+            node,
+            isUntypedFunctionExpressionNode()
+                .withParams(isUntypedParamsNode(
+                    isSequence(
+                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
+                    ),
+                    isSequence(
+                        isUntypedParamNode("b", isUntypedTypeLevelReferenceNode("String"))
+                    )
+                ))
+        );
+    }
+
+    @Test
+    public void cannotParsePositionalParamAfterNamedParam() {
+        var source = """
+            fn (.a: Int, b: String) -> Unit {
+            }""";
+
+        assertThrows(
+            PositionalParamAfterNamedParamError.class,
+            () -> parseString(source, Parser::parseTopLevelExpression)
+        );
+    }
+
+    @Test
+    public void paramsCanHaveTrailingComma() {
+        var source = """
+            fn (a: Int, ) -> Unit {
+            }""";
+
+        var node = parseString(source, Parser::parseTopLevelExpression);
+
+        assertThat(
+            node,
+            isUntypedFunctionExpressionNode()
+                .withParams(isUntypedParamsNode(
+                    isSequence(
+                        isUntypedParamNode("a", isUntypedTypeLevelReferenceNode("Int"))
+                    ),
+                    isSequence()
+                ))
+        );
+    }
+
+    @Test
+    public void canParseFunctionWithEffect() {
+        var source = """
+            fn () ! Io -> Unit {
+            }""";
+
+        var node = parseString(source, Parser::parseTopLevelExpression);
+
+        assertThat(
+            node,
+            isUntypedFunctionExpressionNode()
+                .withEffect(isOptionalOf(isUntypedTypeLevelReferenceNode("Io")))
+        );
+    }
+
+    @Test
+    public void canParseFunctionWithBodyWithoutReturn() {
+        var source = """
+            fn () -> Unit {
+                a;
+                b;
+                c;
+            }""";
+
+        var node = parseString(source, Parser::parseTopLevelExpression);
+
+        assertThat(
+            node,
+            isUntypedFunctionExpressionNode()
+                .withBody(isUntypedBlockNode(isSequence(
+                    isUntypedExpressionStatementNode(isUntypedReferenceNode("a")),
+                    isUntypedExpressionStatementNode(isUntypedReferenceNode("b")),
+                    isUntypedExpressionStatementNode(isUntypedReferenceNode("c"))
+                )))
+        );
+    }
+
+    @Test
+    public void canParseFunctionWithBodyWithBlockReturn() {
+        var source = """
+            fn () -> Unit {
+                a;
+                b;
+                c
+            }""";
+
+        var node = parseString(source, Parser::parseTopLevelExpression);
+
+        assertThat(
+            node,
+            isUntypedFunctionExpressionNode()
+                .withBody(isUntypedBlockNode(isSequence(
+                    isUntypedExpressionStatementNode(isUntypedReferenceNode("a")),
+                    isUntypedExpressionStatementNode(isUntypedReferenceNode("b")),
+                    isUntypedBlockReturnNode(isUntypedReferenceNode("c"))
+                )))
+        );
+    }
+
+    @Test
+    public void blockReturnEndsFunction() {
+        var source = """
+            fn () -> Unit {
+                a;
+                b
+                c
+            }""";
+
+        var error = assertThrows(
+            UnexpectedTokenException.class,
+            () -> parseString(source, Parser::parseTopLevelExpression)
+        );
+
+        assertThat(error.getActual().value(), equalTo("c"));
+        assertThat(error.getExpected(), equalTo(TokenType.SYMBOL_BRACE_CLOSE.toString()));
+    }
+}