Start hacking on "if" expressions.

test/block_syntax.wren

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+// Single line.
+{ io.write("ok") }.call // expect: ok
+
+// No trailing newline.
+{
+  io.write("ok") }.call // expect: ok
+
+// Trailing newline.
+{
+  io.write("ok") // expect: ok
+}.call
+
+// Multiple expressions.
+{
+  io.write("1") // expect: 1
+  io.write("2") // expect: 2
+}.call
+
+// Extra newlines.
+{
+
+
+  io.write("1") // expect: 1
+
+
+  io.write("2") // expect: 2
+
+
+}.call
+
+// TODO(bob): Arguments.

test/if_syntax.wren

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+// Evaluate the 'then' expression if the condition is true.
+if (true) io.write("good") // expect: good
+if (false) io.write("bad")
+
+// Evaluate the 'else' expression if the condition is false.
+if (true) io.write("good") else io.write("bad") // expect: good
+if (false) io.write("bad") else io.write("good") // expect: good
+
+// Return the 'then' expression if the condition is true.
+io.write(if (true) "good") // expect: good
+
+// Return null if the condition is false and there is no else.
+io.write(if (false) "bad") // expect: null
+
+// Return the 'else' expression if the condition is false.
+io.write(if (false) "bad" else "good") // expect: good