feat: ADR-0035 4a — SQL type-alias resolver (Type::from_sql_name)

Advanced-mode SQL type slot accepts the ten playground keywords plus the
standard-SQL aliases (integer/varchar/timestamp/numeric/float/double
precision/binary/..., case-insensitive). Simple-mode FromStr is unchanged
(rejects aliases). Unknown names -> None for the friendly diagnostic.

src/dsl/types.rs

@@ -134,6 +134,41 @@ impl Type {
             other => other,
         }
     }
+
+    /// Resolve a type name from the **advanced-mode SQL** type slot
+    /// (ADR-0035 §3). Accepts the ten playground keywords *and* the
+    /// standard-SQL aliases mapped onto them. Case-insensitive;
+    /// internal whitespace is collapsed so `double precision` resolves
+    /// regardless of spacing. Returns `None` for an unrecognised name —
+    /// the caller turns that into the friendly "unknown type"
+    /// diagnostic.
+    ///
+    /// Deliberately distinct from [`FromStr`](std::str::FromStr), which
+    /// is the *simple-mode* parser and accepts only the ten keywords
+    /// (no aliases), so simple mode teaches the playground's own
+    /// vocabulary. A length/precision argument (`varchar(255)`) is
+    /// stripped by the grammar before the name reaches this resolver.
+    #[must_use]
+    pub fn from_sql_name(name: &str) -> Option<Self> {
+        // Collapse internal whitespace (for the two-word
+        // `double precision`) and lowercase for case-insensitive match.
+        let normalised = name
+            .split_whitespace()
+            .collect::<Vec<_>>()
+            .join(" ")
+            .to_ascii_lowercase();
+        match normalised.as_str() {
+            "integer" | "smallint" | "bigint" => Some(Self::Int),
+            "varchar" | "char" => Some(Self::Text),
+            "boolean" => Some(Self::Bool),
+            "timestamp" => Some(Self::DateTime),
+            "numeric" => Some(Self::Decimal),
+            "float" | "double precision" => Some(Self::Real),
+            "binary" | "varbinary" => Some(Self::Blob),
+            // Fall through to the canonical ten keywords.
+            other => other.parse::<Self>().ok(),
+        }
+    }
 }
 
 impl fmt::Display for Type {
@@ -284,4 +319,64 @@ mod tests {
             );
         }
     }
+
+    // --- ADR-0035 §3: advanced-mode SQL type-name resolution ---
+    // `from_sql_name` accepts the ten playground keywords *and* the
+    // standard-SQL aliases. Simple-mode `FromStr` is unchanged (it
+    // still rejects aliases — see `unknown_type_lists_expected_alternatives`).
+
+    #[test]
+    fn sql_resolver_accepts_the_ten_canonical_keywords() {
+        for &ty in Type::all() {
+            assert_eq!(Type::from_sql_name(ty.keyword()), Some(ty));
+        }
+    }
+
+    #[test]
+    fn sql_resolver_maps_standard_sql_aliases() {
+        for (alias, expected) in [
+            ("integer", Type::Int),
+            ("smallint", Type::Int),
+            ("bigint", Type::Int),
+            ("varchar", Type::Text),
+            ("char", Type::Text),
+            ("boolean", Type::Bool),
+            ("timestamp", Type::DateTime),
+            ("numeric", Type::Decimal),
+            ("float", Type::Real),
+            ("double precision", Type::Real),
+            ("binary", Type::Blob),
+            ("varbinary", Type::Blob),
+        ] {
+            assert_eq!(
+                Type::from_sql_name(alias),
+                Some(expected),
+                "alias `{alias}` should map to {expected:?}"
+            );
+        }
+    }
+
+    #[test]
+    fn sql_resolver_is_case_insensitive() {
+        assert_eq!(Type::from_sql_name("INTEGER"), Some(Type::Int));
+        assert_eq!(Type::from_sql_name("VarChar"), Some(Type::Text));
+        assert_eq!(Type::from_sql_name("Double Precision"), Some(Type::Real));
+        assert_eq!(Type::from_sql_name("TEXT"), Some(Type::Text));
+    }
+
+    #[test]
+    fn sql_resolver_rejects_genuinely_unknown_names() {
+        assert_eq!(Type::from_sql_name("money"), None);
+        assert_eq!(Type::from_sql_name("json"), None);
+        assert_eq!(Type::from_sql_name(""), None);
+    }
+
+    #[test]
+    fn sql_resolver_does_not_accept_serial_aliases() {
+        // `serial`/`shortid` are playground-only; there is no standard
+        // alias for them, and INTEGER PRIMARY KEY does NOT become serial
+        // (ADR-0035 §3 — that is enforced at the PK layer, not here).
+        assert_eq!(Type::from_sql_name("serial"), Some(Type::Serial));
+        assert_eq!(Type::from_sql_name("autoincrement"), None);
+    }
 }