[fine] Tweak syntax for assertions to make me happier

fine/build.rs

@@ -17,7 +17,7 @@ fn generate_test_for_file(path: PathBuf) -> String {
         };
 
         let line = line.trim();
-        if line == "concrete:" {
+        if line == "@concrete:" {
             let mut concrete = String::new();
             while let Some(line) = lines.next() {
                 let line = match line.strip_prefix("// | ") {
@@ -32,7 +32,7 @@ fn generate_test_for_file(path: PathBuf) -> String {
             assertions.push(quote! {
                 crate::assert_concrete(&_tree, #concrete, #display_path);
             });
-        } else if let Some(line) = line.strip_prefix("type:") {
+        } else if let Some(line) = line.strip_prefix("@type:") {
             let (pos, expected) = line
                 .trim()
                 .split_once(' ')
@@ -45,7 +45,7 @@ fn generate_test_for_file(path: PathBuf) -> String {
             assertions.push(quote! {
                 crate::assert_type_at(&_tree, &_lines, #pos, #expected, #display_path);
             });
-        } else if let Some(line) = line.strip_prefix("type-error:") {
+        } else if let Some(line) = line.strip_prefix("@type-error:") {
             let (pos, expected) = line
                 .trim()
                 .split_once(' ')

fine/tests/README.md

@@ -0,0 +1,79 @@
+# Snapshot Tests
+
+The `.fine` files in this directory and its descendants are processed
+by `build.rs` into a series of snapshot-tests. The various test
+assertions are specified by `@` directives in comments in the file.
+
+e.g., a test might look like this:
+
+```fine
+// @concrete:
+// | File
+// |   ExpressionStatement
+// |     BinaryExpression
+// |       BinaryExpression
+// |         LiteralExpression
+// |           Number:'"1"'
+// |         Star:'"*"'
+// |         LiteralExpression
+// |           Number:'"2"'
+// |       Plus:'"+"'
+// |       BinaryExpression
+// |         UnaryExpression
+// |           Minus:'"-"'
+// |           LiteralExpression
+// |             Number:'"3"'
+// |         Star:'"*"'
+// |         LiteralExpression
+// |           Number:'"4"'
+// |     Semicolon:'";"'
+//
+1 * 2 + -3 * 4;
+
+// @type: 532 f64
+```
+
+## Assertions
+
+The various assertions are as follows:
+
+- The `// @concrete:` assertion says that the following lines
+  (prefixed with `// | `, as above) describe the concrete syntax tree
+  of the file after parsing.
+
+  e.g.:
+
+  ```fine
+  // @concrete:
+  // | File
+  // |   ExpressionStatement
+  // |     LiteralExpression
+  // |       String:'"\"Hello world\""'
+  // |     Semicolon:'";"'
+  //
+  "Hello world";
+  ```
+
+- The `// @type:` assertion says that the type of the tree at the
+  given point will match the given type. `@type` assertions usually go
+  after the contents of the file to make the probe points more stable
+  in the face of new assertions and whatnot.
+
+  e.g.:
+
+  ```fine
+  "Hello world!"
+  // @type: 2 string
+  ```
+
+- The `// @type-error:` assertion says that the type of the tree at
+  the given point should be an error, and that the error message
+  provided should be among the generated errors. (Like `@type`, these
+  usually go after the code, for stability.)
+
+  e.g.:
+
+  ```fine
+  - "twenty five";
+  // @type-error: 0 cannot apply unary operator '-' to value of type string
+  ```

fine/tests/expression/arithmetic.fine

@@ -1,4 +1,4 @@
-// concrete:
+// @concrete:
 // | File
 // |   ExpressionStatement
 // |     BinaryExpression
@@ -21,4 +21,4 @@
 //
 1 * 2 + -3 * 4;
 
-// type: 532 f64
+// @type: 532 f64

fine/tests/expression/boolean.fine

@@ -1,4 +1,4 @@
-// concrete:
+// @concrete:
 // | File
 // |   ExpressionStatement
 // |     BinaryExpression
@@ -21,4 +21,4 @@
 //
 true and false or false and !true;
 
-// type: 549 bool
+// @type: 549 bool

fine/tests/expression/conditional.fine

@@ -1,4 +1,4 @@
-// concrete:
+// @concrete:
 // | File
 // |   IfStatement
 // |     ConditionalExpression
@@ -27,18 +27,18 @@ if true { "discarded"; 23 } else { 45 }
 
 // Here come some type probes!
 // (type of the condition)
-// type: 667 bool
+// @type: 667 bool
 //
 // (the discarded expression)
-// type: 674 string
+// @type: 674 string
 //
 // (the "then" clause)
-// type: 686 f64
-// type: 689 f64
+// @type: 686 f64
+// @type: 689 f64
 //
 // (the "else" clause)
-// type: 696 f64
-// type: 699 f64
+// @type: 696 f64
+// @type: 699 f64
 //
 // (the overall expression)
-// type: 664 f64
+// @type: 664 f64

fine/tests/expression/errors/binary_mismatch.fine

@@ -1,4 +1,4 @@
 112 - "twenty five";
 "twenty five" - 112;
-// type-error: 4 cannot apply binary operator '-' to expressions of type 'f64' (on the left) and 'string' (on the right)
-// type-error: 35 cannot apply binary operator '-' to expressions of type 'string' (on the left) and 'f64' (on the right)
+// @type-error: 4 cannot apply binary operator '-' to expressions of type 'f64' (on the left) and 'string' (on the right)
+// @type-error: 35 cannot apply binary operator '-' to expressions of type 'string' (on the left) and 'f64' (on the right)

fine/tests/expression/errors/if_mismatched_arms.fine

@@ -1,2 +1,2 @@
 if true { "blarg" } else { 23 }
-// type-error: 0 the type of the `then` branch (string) must match the type of the `else` branch (f64)
+// @type-error: 0 the type of the `then` branch (string) must match the type of the `else` branch (f64)

fine/tests/expression/errors/if_not_bool.fine

@@ -1,2 +1,2 @@
 if 23 { "what" } else { "the" }
-// type-error: 0 conditions must yield a boolean
+// @type-error: 0 conditions must yield a boolean

fine/tests/expression/errors/if_requires_else.fine

@@ -1,2 +1,2 @@
 if (if false { true }) { 32 } else { 23 }
-// type-error: 4 the type of the `then` branch (bool) must match the type of the `else` branch (())
+// @type-error: 4 the type of the `then` branch (bool) must match the type of the `else` branch (())

fine/tests/expression/errors/unary_mismatch.fine

@@ -1,2 +1,2 @@
 - "twenty five";
-// type-error: 0 cannot apply unary operator '-' to value of type string
+// @type-error: 0 cannot apply unary operator '-' to value of type string

fine/tests/expression/number.fine

@@ -1,4 +1,4 @@
-// concrete:
+// @concrete:
 // | File
 // |   ExpressionStatement
 // |     LiteralExpression
@@ -7,4 +7,4 @@
 
 42;
 
-// type: 129 f64
+// @type: 129 f64

fine/tests/expression/strings.fine

@@ -1,4 +1,4 @@
-// concrete:
+// @concrete:
 // | File
 // |   ExpressionStatement
 // |     BinaryExpression
@@ -11,4 +11,4 @@
 //
 "Hello " + 'world!';
 
-// type: 261 string
+// @type: 261 string