Add statements to the guide

Closes #11

guide/guide.md

@@ -42,6 +42,158 @@ move |arg1: i32, arg2: i32| -> i32 { expr1; expr2 }
 Use spaces, not tabs.
 
 
+### Statements
+
+#### Let statements
+
+There should be spaces after the `:` and on both sides of the `=` (if they are
+present). No space before the semi-colon.
+
+```rust
+// A comment.
+let pattern: Type = expr;
+
+let pattern;
+let pattern: Type;
+let pattern = expr;
+```
+
+If possible the declaration should be formatted on a single line. If this is not
+possible, then try splitting after the `=`, if the declaration can fit on two
+lines. The expression should be block indented.
+
+```rust
+let pattern: Type =
+    expr;
+```
+
+If the first line does not fit on a single line, then split after the colon,
+using block indentation. If the type covers multiple lines, even after line-
+breaking after the `:`, then the first line may be placed on the same line as
+the `:`, subject to the [combining rules](https://github.com/rust-lang-nursery/fmt-rfcs/issues/61) (WIP).
+
+
+```rust
+let pattern:
+    Type =
+    expr;
+```
+
+e.g,
+
+```rust
+let Foo {
+    f: abcd,
+    g: qwer,
+}: Foo<Bar> =
+    Foo { f, g };
+
+let (abcd,
+     defg):
+    Baz =
+{ ... }
+```
+
+If the expression covers multiple lines, if the first line of the expression
+fits in the remaining space, it stays on the same line as the `=`, the rest of the
+expression is not indented. If the first line does not fit, then it should start
+on the next lines, and should be block indented. If the expression is a block
+and the type or pattern cover multiple lines, then the opening brace should be
+on a new line and not indented (this provides separation for the interior of the
+block from the type), otherwise the opening brace follows the `=`.
+
+Examples:
+
+```rust
+let foo = Foo {
+    f: abcd,
+    g: qwer,
+};
+
+let foo =
+    ALongName {
+        f: abcd,
+        g: qwer,
+    };
+
+let foo: Type = {
+    an_expression();
+    ...
+};
+
+let foo:
+    ALongType =
+{
+    an_expression();
+    ...    
+};
+
+let Foo {
+    f: abcd,
+    g: qwer,
+}: Foo<Bar> = Foo {
+    f: blimblimblim, 
+    g: blamblamblam,
+};
+
+let Foo {
+    f: abcd,
+    g: qwer,
+}: Foo<Bar> = foo(
+    blimblimblim,
+    blamblamblam,
+);
+```
+
+
+#### Macros in statement position
+
+A macro use in statement position should use parentheses or square brackets as
+delimiters and should be terminated with a semi-colon. There should be no spaces
+between the name, `!`, the delimiters, or the `;`.
+
+```rust
+// A comment.
+a_macro!(...);
+```
+
+
+#### Expressions in statement position
+
+There should be no space between the expression and the semi-colon.
+
+<expr>;
+
+All expressions in statement position should be terminated with a semi-colon,
+unless they end with a block or are used as the value for a block.
+
+E.g.,
+
+```rust
+{
+    an_expression();
+    expr_as_value()
+}
+
+return foo();
+
+loop {
+    break;
+}
+```
+
+Use a semi-colon where an expression has void type, even if it could be
+propagated. E.g.,
+
+```rust
+fn foo() { ... }
+
+fn bar() {
+    foo();
+}
+```
+
+
 ### Expressions
 
 Do not include a space between a unary op and its operand (i.e., `!x`, not